热寂

2021-10-13T12:14:40Z

Fernando：

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{{For|the album by Off Minor|The Heat Death of the Universe}}

'''宇宙的热寂'''，也被称为大寒或大冻结<ref>[http://map.gsfc.nasa.gov/universe/uni_fate.html WMAP – Fate of the Universe], ''WMAP's Universe'', [[NASA]]. Accessed online July 17, 2008.</ref>，是对宇宙最终命运的猜测，这表明宇宙将进化到没有热力学自由能的状态，因此将无法维持熵增的过程。热寂并不意味着任何特定的绝对温度; 它只要求温差或其他过程可能不再被利用来进行做工。用物理学的语言来说，此时宇宙达到热力学平衡（最大熵）。

如果宇宙的拓扑结构是开放的或平坦的，或者如果暗能量是一个正的宇宙学常数（两者都与目前的数据一致），宇宙将永远继续膨胀，预计会出现热寂<ref name="DftS">
If the topology of the universe is open or flat, or if dark energy is a positive cosmological constant (both of which are consistent with current data), the universe will continue expanding forever, and a heat death is expected to occur, with the universe cooling to approach equilibrium at a very low temperature after a very long time period.

如果宇宙的拓扑结构是开放的或者是平坦的，或者暗能量是一个正宇宙学常数(两者都与当前的数据一致) ，那么宇宙将永远继续膨胀，并且预计会发生热死亡，在很长一段时间后，宇宙将在一个非常低的温度下达到平衡。

{{Cite book

| title = Death from the Skies!

The hypothesis of heat death stems from the ideas of Lord Kelvin, who in the 1850s took the theory of heat as mechanical energy loss in nature (as embodied in the first two laws of thermodynamics) and extrapolated it to larger processes on a universal scale.

热死的假说来源于开尔文勋爵的思想，他在19世纪50年代把热理论看作是自然界中的机械能损失(正如前两个热力学定律所体现的那样) ，并将其推广到普遍规模的更大过程中。

| last = Plait

| first = Philip

| publisher = Viking Adult

The concept of the heat death of the universe is based on the observation that the gravitational potential energy of the universe, also known as rest mass that is stored mostly in baryons, self‑gravitationally shrinks and heats up to ever higher temperatures. Consequently, the ever‑smaller and ever‑hotter baryons "evaporate", with an exponential acceleration, into the seemingly expanding ambient space as photons, so that eventually the universe will consist of zero‑frequency photons:

宇宙热死的概念是基于这样的观察: 宇宙的重力位能量，也被称为剩余质量，大部分储存在重子中，自我; 引力收缩和加热到更高的温度。因此，越来越小、越来越热的重子以指数加速“蒸发” ，进入看似正在扩张的周围空间，成为光子，因此最终宇宙将由频率为0的光子组成:

| isbn = 978-0-670-01997-7

<blockquote>

< 我们的目标是什么 >

| publication-date = 16 October 2008

If the rest mass decreases by Δm0, the kinetic energy E = c2Δm0 is produced. The same thing is true if we replace production of kinetic energy E by production of radiant energy E. Continuing this line of argument, one can envisage the possibility that the whole rest mass m of a body could be converted into energy. Then the energy E = m0c2 would be produced and the whole rest mass of the body would disappear.

如果静止质量减小到 δm 0 ，动能 e = c 2 δm 0 。如果我们用辐射能的产生来代替动能的产生，情况也是如此。继续这一论点，我们可以设想一个物体的整个静止质量 m 可以转化为能量的可能性。然后产生能量 e = m 0 c 2 ，使整个身体的静止质量消失。

| pages = 259

—[https://dokumen.pub/qdownload/international-encyclopedia-of-unified-science-vol-1-nos-6-10.html International Encyclopedia of Unified Science] Vol. 1, nos. 6–10, University of Chicago Press, 1955, p. 460

国际统一科学百科全书 https://dokumen.pub/qdownload/International-Encyclopedia-of-Unified-Science-Vol-1-nos-6-10.html。1，no.6-10，芝加哥大学出版社，1955，第460页

| author-link = Phil Plait

</blockquote>

</blockquote >

| title-link = Death from the Skies!

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< 我们的目标是什么 >

| year = 2008

Although mechanical energy is indestructible, there is a universal tendency to its dissipation, which produces throughout the system a gradual augmentation and diffusion of heat, cessation of motion and exhaustion of the potential energy of the material Universe.

虽然机械能是坚不可摧的，但是它的耗散有一种普遍的趋势，这种趋势使整个系统产生热量的逐渐增加和扩散、运动停止和物质宇宙的势能耗尽。

}}</ref>。也就是说，宇宙在很长一段时间后会冷却到很低的温度保持平衡。

——汤姆森，威廉。[http://zapatopi.net/kelvin/papers/on_the_age_of_the_suns_heat.html 论太阳热能的年龄]，麦克米伦杂志，1862年3月5日，388–93页

热寂的假设源于开尔文勋爵的想法，他在19世纪50年代将热力学理论作为自然界的机械能量损失（体现在热力学的前两个定律中）的解释，并将其外推到全球范围内的更大过程。

==概念==

< 我们的目标是什么 >

热寂的概念是基于这样的观察：宇宙的重力势能，也被称为主要储存在重子中的静止质量，会进行自我重力式地收缩并加热到越来越高的温度。因此，越来越小、越来越热的重子以指数级的加速度 "蒸发 "到看似膨胀的环境空间中，成为光子。所以，最终宇宙将由零频率的光子组成。

所有的变化都是相对的。相对于我们常见的物质标准，宇宙正在扩张; 相对于宇宙的大小，我们的物质标准在不断缩小。“膨胀宇宙”理论也可以称为“收缩原子”理论。

亚瑟·爱丁顿曾经描述过重子蒸发的指数加速:<blockquote>那么，让我们把整个宇宙作为我们的恒定标准，并采用一个宇宙存在的观点，其身体由星系间的空间组成，并随着它们的膨胀而膨胀。或者更确切地说，我们现在必须说它保持了同样的规模，因为它不会承认是它改变了。观察这几千万年的历史，它看到我们在缩小：原子、动物、行星，甚至星系，都同样在缩小。只有星系间的空间保持不变。地球绕着太阳旋转，轨道越来越小。把它不断变化的演变当作一个固定的时间单位是荒谬的。宇宙的存在将自然地把他的长度和时间单位联系起来，使光速保持不变。而我们的岁月将在宇宙的时间尺度上以几何级数递减。在那个尺度上，人的生命变得越来越短暂，他的三十岁和十岁是一个不断减少的限额。由于几何级数的特性，我们的无限年数加起来将是一个有限的宇宙时间；因此，我们应该称之为永恒的结束只是宇宙日历中一个普通的有限日期。但是在那一天，宇宙在我们的推算中已经膨胀到无穷大，而我们在宇宙存在的推算中已经缩小到什么也没有。(只提供英文版本)

如果静止质量减少了 Δ''m''0就会产生''E'' = ''c''2Δ''m''0的动能。如果我们用辐射能''E'' 的产生代替动能''E''的产生，情况也是一样的。继续这一论证思路，我们可以设想，一个物体的全部静止质量''m'' 转化为能量的可能性。于是 ''E'' = ''m''0''c''2的能量会被产生，而物体整个的静止质量就会消失。

我们行走在生命的舞台上，为了宇宙观众的利益而进行戏剧表演。随着场景的发展，它注意到演员变得越来越小，动作也越来越快。当最后一幕开始时，幕布升起，侏儒演员以疯狂的速度冲过他们的角色。越来越小。越来越快。发生了最后一次强烈的激动的微观模糊现象。然后就什么都没有了。

:—[https://dokumen.pub/qdownload/international-encyclopedia-of-unified-science-vol-1-nos-6-10.html International Encyclopedia of Unified Science] Vol. 1, nos. 6–10, University of Chicago Press, 1955, p. 460

—Eddington, Arthur. [https://archive.org/details/in.ernet.dli.2015.220736/page/n105/mode/2up The Expanding Universe] CUP, 1933年，90–92页</blockquote>虽然机械能是不可破坏的，但它有一个普遍的耗散趋势，这在整个系统中产生了热量的逐渐增加和扩散、运动的停止和物质宇宙的势能的耗尽。<blockquote>

After the evaporation of all baryons, the resultant bath of zero‑frequency photons, indistinguishable from empty space, will condense into new protons, each miles across, which will undergo another 13.8‑billion‑year‑long exponentially accelerating shrinkage and evaporation. And so ad infinitum:

在所有重子蒸发之后，由此产生的频率为0的光子浴---- 与空空难以分辨---- 将凝结成新的质子，每英里宽，这将经历另一个13.8亿的长指数加速收缩和蒸发。所以永无止境:

:—Thomson, William. [http://zapatopi.net/kelvin/papers/on_the_age_of_the_suns_heat.html On the Age of the Sun’s Heat] ''Macmillan's Magazine'', 5 March 1862, pp. 388–93

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< 我们的目标是什么 >

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According to the standard view, dark energy will lead the universe into an eternal accelerating expansion. Every bit of matter will eventually lose contact with every other bit. "It all just seemed unbelievably boring to me," Penrose says. Then he found something interesting within it: at the very end of the universe, the only remaining particles will be massless. That means everything that exists will travel at the speed of light, making the flow of time meaningless. After a few mathematical manipulations of infinity, out popped a never‑ending universe, where new big bangs are the inevitable result of a universe's demise. In Penrose's theory, one cosmos leads to another. "I used to call it a crazy scheme, but I'm starting to believe it now," he says.

根据标准观点，暗能量将导致宇宙进入永恒的加速膨胀。每一点物质最终都会与其他每一点失去联系。彭罗斯说: “对我来说，这一切都令人难以置信地无聊。”。然后他在其中发现了一些有趣的东西: 在宇宙的尽头，仅存的粒子将是无质量的。这意味着所有存在的事物都将以光速传播，使得时间的流动变得毫无意义。经过一些数学上的无限操作，一个永远不会结束的宇宙出现了，新的宇宙大爆炸是宇宙灭亡的必然结果。在彭罗斯的理论中，一个宇宙导致另一个宇宙。“我过去常说这是一个疯狂的计划，但现在我开始相信了，”他说。

—Brooks, Michael. [https://web.archive.org/web/20160413033955/http:/www.newscientist.com/article/mg20527511-300-roger-penrose-non-stop-cosmos-non-stop-career/ Roger Penrose: Non-stop cosmos, non-stop career] New Scientist, 10 March 2010

ー布鲁克斯，迈克尔。Https://web.archive.org/web/20160413033955/http:/www.newscientist.com/article/mg20527511-300-Roger-Penrose-Non-stop-cosmos-Non-stop-career/ : 《新科学家》，2010年3月10日

The exponential acceleration of [[baryon]]s' evaporation has been described by [[Arthur Eddington]]:

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<blockquote>

All change is relative. The universe is expanding relatively to our common material standards; our material standards are shrinking relatively to the size of the universe. The theory of the "expanding universe" might also be called the theory of the "shrinking atom". <...>

Let us then take the whole universe as our standard of constancy, and adopt the view of a cosmic being whose body is composed of intergalactic spaces and swells as they swell. Or rather we must now say it keeps the same size, for he will not admit that it is he who has changed. Watching us for a few thousand million years, he sees us shrinking; atoms, animals, planets, even the galaxies, all shrink alike; only the intergalactic spaces remain the same. The earth spirals round the sun in an ever‑decreasing orbit. It would be absurd to treat its changing revolution as a constant unit of time. The cosmic being will naturally relate his units of length and time so that the velocity of light remains constant. Our years will then decrease in geometrical progression in the cosmic scale of time. On that scale man's life is becoming briefer; his threescore years and ten are an ever‑decreasing allowance. Owing to the property of geometrical progressions an infinite number of our years will add up to a finite cosmic time; so that what we should call the end of eternity is an ordinary finite date in the cosmic calendar. But on that date the universe has expanded to infinity in our reckoning, and we have shrunk to nothing in the reckoning of the cosmic being.

The idea of heat death stems from the second law of thermodynamics, of which one version states that entropy tends to increase in an isolated system. From this, the hypothesis implies that if the universe lasts for a sufficient time, it will asymptotically approach a state where all energy is evenly distributed. In other words, according to this hypothesis, there is a tendency in nature to the dissipation (energy transformation) of mechanical energy (motion) into thermal energy; hence, by extrapolation, there exists the view that, in time, the mechanical movement of the universe will run down as work is converted to heat because of the second law.

热死的概念来源于热力学第二定律，其中一种说法认为，在一个孤立的系统中，熵倾向于增加。由此，该假设暗示，如果宇宙持续足够长的时间，它将渐近地接近所有能量均匀分布的状态。换句话说，根据这一假设，在自然界中存在着将机械能(运动)耗散(能量转换)为热能的趋势; 因此，通过外推，存在着这样一种观点，即随着时间的推移，宇宙的机械运动将减少，因为根据第二定律，功转换为热。

'''We walk the stage of life, performers of a drama for the benefit of the cosmic spectator. As the scenes proceed he notices that the actors are growing smaller and the action quicker. When the last act opens the curtain rises on midget actors rushing through their parts at frantic speed. Smaller and smaller. Faster and faster. One last microscopic blurr of intense agitation. And then nothing.'''

:—Eddington, Arthur. [https://archive.org/details/in.ernet.dli.2015.220736/page/n105/mode/2up The Expanding Universe] CUP, 1933, pp. 90–92

The conjecture that all bodies in the universe cool off, eventually becoming too cold to support life, seems to have been first put forward by the French astronomer Jean Sylvain Bailly in 1777 in his writings on the history of astronomy and in the ensuing correspondence with Voltaire. In Bailly's view, all planets have an internal heat and are now at some particular stage of cooling. Jupiter, for instance, is still too hot for life to arise there for thousands of years, while the Moon is already too cold. The final state, in this view, is described as one of "equilibrium" in which all motion ceases.

宇宙中的所有物体都会冷却，最终变得太冷以至于无法维持生命，这一猜想似乎最早是由法国天文学家让·西尔万·巴伊于1777年在他关于天文学史的著作中以及随后与伏尔泰的通信中提出的。在贝利看来，所有的行星都有内部热量，现在正处于某个特定的冷却阶段。例如，木星仍然太热，几千年来无法形成生命，而月球已经太冷了。在这种观点中，最终状态被描述为一种“平衡” ，在这种平衡中，所有的运动都停止了。

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The idea of heat death as a consequence of the laws of thermodynamics, however, was first proposed in loose terms beginning in 1851 by Lord Kelvin (William Thomson), who theorized further on the mechanical energy loss views of Sadi Carnot (1824), James Joule (1843) and Rudolf Clausius (1850). Thomson's views were then elaborated over the next decade by Hermann von Helmholtz and William Rankine.

然而，热死作为热力学定律的后果的想法最早是在1851年由开尔文勋爵(William Thomson)以宽松的术语提出的，他进一步从萨迪 · 卡诺(1824年)、詹姆斯 · 朱尔(1843年)和鲁道夫 · 克劳修斯(1850年)的机械能损失观点进行理论化。在接下来的十年里，赫尔曼·冯·亥姆霍兹和威廉 · 兰金详细阐述了汤姆森的观点。

After the evaporation of all [[baryon]]s, the resultant bath of zero‑frequency photons, indistinguishable from empty space, will condense into new [[proton]]s, each miles across, which will undergo another 13.8‑billion‑year‑long exponentially accelerating shrinkage and evaporation. And so ''ad infinitum'':

<blockquote>

According to the standard view, dark energy will lead the universe into an eternal accelerating expansion. Every bit of matter will eventually lose contact with every other bit. "It all just seemed unbelievably boring to me," Penrose says. Then he found something interesting within it: '''at the very end of the universe, the only remaining particles will be massless. That means everything that exists will travel at the speed of light, making the flow of time meaningless.''' After a few mathematical manipulations of infinity, out popped a never‑ending universe, where new big bangs are the inevitable result of a universe's demise. In Penrose's theory, one cosmos leads to another. "I used to call it a crazy scheme, but I'm starting to believe it now," he says.

The idea of heat death of the universe derives from discussion of the application of the first two laws of thermodynamics to universal processes. Specifically, in 1851, Lord Kelvin outlined the view, as based on recent experiments on the dynamical theory of heat: "heat is not a substance, but a dynamical form of mechanical effect, we perceive that there must be an equivalence between mechanical work and heat, as between cause and effect."

宇宙热死的概念来源于前两个热力学定律对宇宙过程的应用的讨论。特别是在1851年，开尔文勋爵根据最近关于热力学理论的实验概述了这一观点: “热不是一种物质，而是一种机械效应的动力形式，我们认为机械功和热之间，如因果之间，必然存在等价关系。”

:—Brooks, Michael. [https://web.archive.org/web/20160413033955/http:/www.newscientist.com/article/mg20527511-300-roger-penrose-non-stop-cosmos-non-stop-career/ Roger Penrose: Non-stop cosmos, non-stop career] ''New Scientist'', 10 March 2010

Lord Kelvin originated the idea of universal heat death in 1852.]]

开尔文爵士在1852年提出了宇宙热死的概念

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In 1852, Thomson published On a Universal Tendency in Nature to the Dissipation of Mechanical Energy, in which he outlined the rudiments of the second law of thermodynamics summarized by the view that mechanical motion and the energy used to create that motion will naturally tend to dissipate or run down. The ideas in this paper, in relation to their application to the age of the Sun and the dynamics of the universal operation, attracted the likes of William Rankine and Hermann von Helmholtz. The three of them were said to have exchanged ideas on this subject. In 1862, Thomson published "On the age of the Sun's heat", an article in which he reiterated his fundamental beliefs in the indestructibility of energy (the first law) and the universal dissipation of energy (the second law), leading to diffusion of heat, cessation of useful motion (work), and exhaustion of potential energy through the material universe, while clarifying his view of the consequences for the universe as a whole. Thomson wrote:

1852年，Thomson 出版了《论自然界中机械能耗散的普遍趋势》一书，其中他概述了热力学第二定律的基本原理，总结为机械运动和用来产生运动的能量会自然地趋于消散或下降。这篇论文中的观点，关于它们在太阳时代和宇宙运行动力学中的应用，吸引了像 William Rankine 和赫尔曼·冯·亥姆霍兹。据说他们三人就这个问题交换了意见。1862年，汤姆森发表了《论太阳热的年龄》一文，重申了他对能量不可毁灭(第一定律)和能量普遍耗散(第二定律)的基本信念，导致热量扩散、有用运动(功)停止以及通过物质宇宙的势能耗尽，同时澄清了他对整个宇宙的后果的看法。汤姆森写道:

==Origins of the idea==

The idea of heat death stems from the [[second law of thermodynamics]], of which one version states that entropy tends to increase in an [[isolated system]]. From this, the hypothesis implies that if the universe lasts for a sufficient time, it will [[asymptotically]] approach a state where all [[energy]] is evenly distributed. In other words, according to this hypothesis, there is a tendency in nature to the [[dissipation]] (energy transformation) of [[mechanical energy]] (motion) into [[thermal energy]]; hence, by extrapolation, there exists the view that, in time, the mechanical movement of the universe will run down as work is converted to heat because of the second law.

<blockquote>The result would inevitably be a state of universal rest and death, if the universe were finite and left to obey existing laws. But it is impossible to conceive a limit to the extent of matter in the universe; and therefore science points rather to an endless progress, through an endless space, of action involving the transformation of potential energy into palpable motion and hence into heat, than to a single finite mechanism, running down like a clock, and stopping for ever.</blockquote>

如果宇宙是有限的，并且遵循现有的法则，那么结果将不可避免地是宇宙的休息和死亡的状态。但是，我们不可能设想宇宙中物质范围的极限; 因此，科学指向的是一个无止境的进步，通过一个无止境的空间，将势能转化为可触知的运动，进而转化为热量，而不是一个单一的有限机制，像时钟一样慢下来，永远停止。</blockquote >

The conjecture that all bodies in the universe cool off, eventually becoming too cold to support life, seems to have been first put forward by the French astronomer [[Jean Sylvain Bailly]] in 1777 in his writings on the history of astronomy and in the ensuing correspondence with [[Voltaire]]. In Bailly's view, all planets have an [[Internal heating|internal heat]] and are now at some particular stage of cooling. [[Jupiter]], for instance, is still too hot for life to arise there for thousands of years, while the [[Moon]] is already too cold. The final state, in this view, is described as one of "equilibrium" in which all motion ceases.<ref>
In the years to follow both Thomson's 1852 and the 1862 papers, Helmholtz and Rankine both credited Thomson with the idea, but read further into his papers by publishing views stating that Thomson argued that the universe will end in a "heat death" (Helmholtz) which will be the "end of all physical phenomena" (Rankine).

在汤姆森1852年和1862年的论文发表后的几年里，亥姆霍兹和兰金都赞扬了汤姆森的这个想法，但他们对汤姆森的论文进行了进一步的解读，发表了自己的观点，认为汤姆森认为宇宙将以“热死亡”(亥姆霍兹)结束，这将是“所有物理现象的终结”(兰金)。

{{Cite book

|title = A History of Modern Planetary Physics: Nebulous Earth

|last = Brush

|first = Stephen G.

Proposals about the final state of the universe depend on the assumptions made about its ultimate fate, and these assumptions have varied considerably over the late 20th century and early 21st century. In a hypothesized "open" or "flat" universe that continues expanding indefinitely, either a heat death or a Big Rip is expected to eventually occur.

关于宇宙最终状态的提议取决于对宇宙最终命运的假设，而这些假设在20世纪晚期和21世纪早期已经发生了相当大的变化。在一个假设的“开放”或“平坦”宇宙，继续膨胀无限期，要么热死或大撕裂预计最终发生。

|author-link = Stephen G. Brush

|publisher = Cambridge University Press

If a Big Rip does not happen long before that, the "heat death" situation could be avoided if there is a method or mechanism to regenerate hydrogen atoms from radiation, dark matter, dark energy, zero-point energy, or other sources. If so, it is at least possible that star formation and heat transfer can continue, avoiding a gradual running down of the universe due to the conversion of matter into energy and heavier elements in stellar processes, and the absorption of matter by black holes and their subsequent evaporation as Hawking radiation.

如果大裂缝不会在那之前很久发生，那么如果有一种方法或机制可以从辐射、暗物质、暗能量、零点能量或其他来源再生氢原子，那么“热死”情况就可以避免。如果是这样的话，至少恒星的形成和热量传递可以继续下去，从而避免了在恒星形成过程中由于物质转化为能量和更重的元素，以及黑洞吸收物质并随之蒸发为霍金辐射而导致的宇宙的逐渐减少。

|year = 1996

|isbn = 978-0-521-44171-1

|volume = 1

|page = [https://archive.org/details/historyofmodernp0000brus/page/77 77]

|url = https://archive.org/details/historyofmodernp0000brus/page/77

From the Big Bang through the present day, matter and dark matter in the universe are thought to have been concentrated in stars, galaxies, and galaxy clusters, and are presumed to continue to do so well into the future. Therefore, the universe is not in thermodynamic equilibrium, and objects can do physical work.:§VID The decay time for a supermassive black hole of roughly 1 galaxy mass (1011 solar masses) due to Hawking radiation is on the order of 10100 years, so entropy can be produced until at least that time. Some large black holes in the universe are predicted to continue to grow up to perhaps 1014 during the collapse of superclusters of galaxies. Even these would evaporate over a timescale of up to 10106 years. After that time, the universe enters the so-called Dark Era and is expected to consist chiefly of a dilute gas of photons and leptons. Over vast periods of time, a spontaneous entropy decrease would eventually occur via the Poincaré recurrence theorem, thermal fluctuations, and fluctuation theorem. Such a scenario, however, has been described as "highly speculative, probably wrong, [and] completely untestable". Sean M. Carroll, originally an advocate of this idea, no longer supports it.

从大爆炸到现在，宇宙中的物质和暗物质被认为集中在恒星、星系和星系团中，并且被认为在未来会继续这样做。因此，宇宙不在热力学平衡，物体可以做物理工作。一个大约有1个星系质量(10个 11个 太阳质量)的超重黑洞，由于霍金辐射的存在，其衰变时间大约为10 100 年，因此至少在那个时间之前，熵是可以产生的。据预测，在超星系团坍缩期间，宇宙中的一些大型黑洞可能会继续增长到10个。即使这些也会在长达10年的时间内蒸发掉。在那之后，宇宙进入了所谓的黑暗时期，预计主要由光子和轻子组成的稀释气体。在大量的时间里，自发的熵减少最终会通过庞加莱始态复现定理、热涨落和涨落定理发生。然而，这种情况被描述为“高度投机，可能是错误的，并且完全不可测试”。最初支持这一观点的肖恩 · m · 卡罗尔不再支持这一观点。

}}</ref>

The idea of heat death as a consequence of the laws of thermodynamics, however, was first proposed in loose terms beginning in 1851 by Lord Kelvin (William Thomson), who theorized further on the mechanical energy loss views of [[Nicolas Léonard Sadi Carnot|Sadi Carnot]] (1824), [[James Joule]] (1843) and [[Rudolf Clausius]] (1850). Thomson's views were then elaborated over the next decade by [[Hermann von Helmholtz]] and [[William Rankine]].{{citation needed|date=November 2015}}

Max Planck wrote that the phrase "entropy of the universe" has no meaning because it admits of no accurate definition. More recently, Walter Grandy writes: "It is rather presumptuous to speak of the entropy of a universe about which we still understand so little, and we wonder how one might define thermodynamic entropy for a universe and its major constituents that have never been in equilibrium in their entire existence." According to Tisza: "If an isolated system is not in equilibrium, we cannot associate an entropy with it." Buchdahl writes of "the entirely unjustifiable assumption that the universe can be treated as a closed thermodynamic system". According to Gallavotti: "... there is no universally accepted notion of entropy for systems out of equilibrium, even when in a stationary state." Discussing the question of entropy for non-equilibrium states in general, Lieb and Yngvason express their opinion as follows: "Despite the fact that most physicists believe in such a nonequilibrium entropy, it has so far proved impossible to define it in a clearly satisfactory way." In Landsberg's opinion: "The third misconception is that thermodynamics, and in particular, the concept of entropy, can without further enquiry be applied to the whole universe. ... These questions have a certain fascination, but the answers are speculations, and lie beyond the scope of this book."

马克斯 · 普朗克写道，“宇宙的熵”这个短语没有任何意义，因为它不承认有准确的定义。最近，Walter Grandy 写道: “我们仍然对宇宙的熵知之甚少，我们想知道如何定义一个宇宙及其主要成分的熵，而这些成分在整个存在过程中从未处于平衡状态。”蒂萨说: “如果一个孤立的系统不处于平衡状态，我们就不能把熵和它联系起来。”布赫达尔写道: “宇宙可以被视为一个封闭的热力学系统，这是完全不合理的假设。”。根据 Gallavotti 的说法: “对于失去平衡的系统，没有普遍接受的熵的概念，即使是在定态中。”在讨论一般非平衡态的熵问题时，Lieb 和 Yngvason 表达了他们的观点如下: “尽管大多数物理学家相信存在这样的非平衡熵，但迄今为止已经证明不可能以一种明显令人满意的方式来定义它。”兰兹伯格认为: “第三个误解是，热力学，特别是熵的概念，不需要进一步探究就可以应用于整个宇宙。...这些问题有一定的吸引力，但答案都是推测，超出了本书的范围。”

===History===

A 2010 analysis of entropy states, "The entropy of a general gravitational field is still not known", and "gravitational entropy is difficult to quantify". The analysis considers several possible assumptions that would be needed for estimates and suggests that the observable universe has more entropy than previously thought. This is because the analysis concludes that supermassive black holes are the largest contributor. Lee Smolin goes further: "It has long been known that gravity is important for keeping the universe out of thermal equilibrium. Gravitationally bound systems have negative specific heat—that is, the velocities of their components increase when energy is removed. ... Such a system does not evolve toward a homogeneous equilibrium state. Instead it becomes increasingly structured and heterogeneous as it fragments into subsystems."

2010年对熵状态的分析表明，“一个普通引力场的熵仍然不为人知” ，“引力熵很难量化”。该分析考虑了几个可能的假设，这些假设对于估计来说是必要的，并且表明可观测宇宙的熵比之前想象的要多。这是因为分析得出结论，超大质量黑洞是最大的贡献者。李 · 斯莫林更进一步说: “人们早就知道，引力对于防止宇宙进入热平衡十分重要。引力束缚系统具有负的比热，也就是说，当能量消失时，其组分的速度增加。...这样的系统不会演化到均匀的平衡状态。相反，随着它分解成子系统，它变得越来越结构化和异构化。”

The idea of heat death of the universe derives from discussion of the application of the first two laws of thermodynamics to universal processes. Specifically, in 1851, Lord Kelvin outlined the view, as based on recent experiments on the dynamical [[theory of heat]]: "heat is not a substance, but a dynamical form of mechanical effect, we perceive that there must be an equivalence between mechanical work and heat, as between cause and effect."<ref>Thomson, Sir William. (1851). [https://zapatopi.net/kelvin/papers/on_the_dynamical_theory_of_heat.html "On the Dynamical Theory of Heat, with numerical results deduced from Mr Joule’s equivalent of a Thermal Unit, and M. Regnault’s Observations on Steam"] Excerpts. [§§1–14 & §§99–100], ''[[Transactions of the Royal Society of Edinburgh]]'', March 1851, and ''[[Philosophical Magazine|Philosophical Magazine IV]]'', 1852. [from ''Mathematical and Physical Papers'', vol. i, art. XLVIII, pp. 174]</ref>

This point of view is also supported by the fact of a recent experimental discovery of a stable non-equilibrium steady state in a relatively simple closed system. It should be expected that an isolated system fragmented into subsystems does not necessarily come to thermodynamic equilibrium and remain in non-equilibrium steady state. Entropy will be transmitted from one subsystem to another, but its production will be zero, which does not contradict the second law of thermodynamics.

最近在一个相对简单的封闭系统中实验发现了稳定的非平衡稳态，这也支持了这一观点。可以预期的是，一个分裂成子系统的孤立系统不一定会达到热力学平衡并保持非平衡的稳定状态。熵将从一个子系统传递到另一个子系统，但是它的产出将为零，这与热力学第二定律并不矛盾。

[[Image:Lord Kelvin photograph.jpg|175px|right|thumb|[[William Thomson, 1st Baron Kelvin|Lord Kelvin]] originated the idea of universal heat death in 1852.|链接=Special:FilePath/Lord_Kelvin_photograph.jpg]]

In 1852, Thomson published ''On a Universal Tendency in Nature to the Dissipation of Mechanical Energy'', in which he outlined the rudiments of the second law of thermodynamics summarized by the view that mechanical motion and the energy used to create that motion will naturally tend to dissipate or run down.<ref>Thomson, Sir William (1852). [https://zapatopi.net/kelvin/papers/on_a_universal_tendency.html "On a Universal Tendency in Nature to the Dissipation of Mechanical Energy"] ''[[Proceedings of the Royal Society of Edinburgh]]'' for 19 April 1852, also ''[[Philosophical Magazine]]'', Oct. 1852. [This version from ''Mathematical and Physical Papers'', vol. i, art. 59, pp. 511.]</ref> The ideas in this paper, in relation to their application to the age of the [[Sun]] and the dynamics of the universal operation, attracted the likes of William Rankine and Hermann von Helmholtz. The three of them were said to have exchanged ideas on this subject.<ref name="Energy and Empire">
{{Cite book

| title = Energy and Empire: A Biographical Study of Lord Kelvin

| last = Smith

| first = Crosbie

| last2 = Wise

| first2 = M. Norton

| publisher = Cambridge University Press

| year = 1989

| isbn = 978-0-521-26173-9

| pages = 500

| author-link2 = M. Norton Wise

}}</ref> In 1862, Thomson published "On the age of the Sun's heat", an article in which he reiterated his fundamental beliefs in the indestructibility of energy (the [[first law of thermodynamics|first law]]) and the universal dissipation of energy (the second law), leading to diffusion of heat, cessation of useful motion ([[work (physics)|work]]), and exhaustion of [[potential energy]] through the material universe, while clarifying his view of the consequences for the universe as a whole. Thomson wrote:

<blockquote>The result would inevitably be a state of universal rest and death, if the universe were finite and left to obey existing laws. But it is impossible to conceive a limit to the extent of matter in the universe; and therefore science points rather to an endless progress, through an endless space, of action involving the transformation of [[potential energy]] into [[Work (physics)|palpable motion]] and hence into [[heat]], than to a single finite mechanism, running down like a clock, and stopping for ever.<ref>

{{Cite magazine

| last = Thomson

| first = Sir William

| date = 5 March 1862

| title = On the Age of the Sun's Heat

| url = https://zapatopi.net/kelvin/papers/on_the_age_of_the_suns_heat.html

| magazine = [[Macmillan's Magazine]]

| volume = 5

| pages = 388–93

}}</ref></blockquote>

类别: 物理宇宙学

In the years to follow both Thomson's 1852 and the 1862 papers, Helmholtz and Rankine both credited Thomson with the idea, but read further into his papers by publishing views stating that Thomson argued that the universe will end in a "''heat death''" (Helmholtz) which will be the "''end of all physical phenomena''" (Rankine).<ref name="Energy and Empire" /><ref>

类别: 热力学熵

分类: 末日情景

类别: 1851年的科学

类别: 宇宙的终极命运

<noinclude>

This page was moved from [[wikipedia:en:Heat death of the universe]]. Its edit history can be viewed at [[热寂/edithistory]]</noinclude>

[[Category:待整理页面]]

热寂

2021-09-29T14:06:01Z

Fernando：

此词条暂由彩云小译翻译，翻译字数共2403，未经人工整理和审校，带来阅读不便，请见谅。

{{For|the album by Off Minor|The Heat Death of the Universe}}

{{article issues|

{{article issues|

{文章问题 |

{{Over-quotation|date=September 2020}}

{{Original research|date=September 2020}}

}}

}}

{{short description|Possible end of the universe}}

{{Physical cosmology|expansion}}

'''宇宙的热寂'''，也被称为大寒或大冻结<ref>[http://map.gsfc.nasa.gov/universe/uni_fate.html WMAP – Fate of the Universe], ''WMAP's Universe'', [[NASA]]. Accessed online July 17, 2008.</ref>，是对宇宙最终命运的猜测，这表明宇宙将进化到没有热力学自由能的状态，因此将无法维持熵增的过程。热寂并不意味着任何特定的绝对温度; 它只要求温差或其他过程可能不再被利用来进行做工。用物理学的语言来说，此时宇宙达到热力学平衡（最大熵）。

如果宇宙的拓扑结构是开放的或平坦的，或者如果暗能量是一个正的宇宙学常数（两者都与目前的数据一致），宇宙将永远继续膨胀，预计会出现热寂<ref name="DftS">
If the topology of the universe is open or flat, or if dark energy is a positive cosmological constant (both of which are consistent with current data), the universe will continue expanding forever, and a heat death is expected to occur, with the universe cooling to approach equilibrium at a very low temperature after a very long time period.

如果宇宙的拓扑结构是开放的或者是平坦的，或者暗能量是一个正宇宙学常数(两者都与当前的数据一致) ，那么宇宙将永远继续膨胀，并且预计会发生热死亡，在很长一段时间后，宇宙将在一个非常低的温度下达到平衡。

{{Cite book

| title = Death from the Skies!

The hypothesis of heat death stems from the ideas of Lord Kelvin, who in the 1850s took the theory of heat as mechanical energy loss in nature (as embodied in the first two laws of thermodynamics) and extrapolated it to larger processes on a universal scale.

热死的假说来源于开尔文勋爵的思想，他在19世纪50年代把热理论看作是自然界中的机械能损失(正如前两个热力学定律所体现的那样) ，并将其推广到普遍规模的更大过程中。

| last = Plait

| first = Philip

| publisher = Viking Adult

The concept of the heat death of the universe is based on the observation that the gravitational potential energy of the universe, also known as rest mass that is stored mostly in baryons, self‑gravitationally shrinks and heats up to ever higher temperatures. Consequently, the ever‑smaller and ever‑hotter baryons "evaporate", with an exponential acceleration, into the seemingly expanding ambient space as photons, so that eventually the universe will consist of zero‑frequency photons:

宇宙热死的概念是基于这样的观察: 宇宙的重力位能量，也被称为剩余质量，大部分储存在重子中，自我; 引力收缩和加热到更高的温度。因此，越来越小、越来越热的重子以指数加速“蒸发” ，进入看似正在扩张的周围空间，成为光子，因此最终宇宙将由频率为0的光子组成:

| isbn = 978-0-670-01997-7

<blockquote>

< 我们的目标是什么 >

| publication-date = 16 October 2008

If the rest mass decreases by Δm0, the kinetic energy E = c2Δm0 is produced. The same thing is true if we replace production of kinetic energy E by production of radiant energy E. Continuing this line of argument, one can envisage the possibility that the whole rest mass m of a body could be converted into energy. Then the energy E = m0c2 would be produced and the whole rest mass of the body would disappear.

如果静止质量减小到 δm 0 ，动能 e = c 2 δm 0 。如果我们用辐射能的产生来代替动能的产生，情况也是如此。继续这一论点，我们可以设想一个物体的整个静止质量 m 可以转化为能量的可能性。然后产生能量 e = m 0 c 2 ，使整个身体的静止质量消失。

| pages = 259

—[https://dokumen.pub/qdownload/international-encyclopedia-of-unified-science-vol-1-nos-6-10.html International Encyclopedia of Unified Science] Vol. 1, nos. 6–10, University of Chicago Press, 1955, p. 460

国际统一科学百科全书 https://dokumen.pub/qdownload/International-Encyclopedia-of-Unified-Science-Vol-1-nos-6-10.html。1，no.6-10，芝加哥大学出版社，1955，第460页

| author-link = Phil Plait

</blockquote>

</blockquote >

| title-link = Death from the Skies!

<blockquote>

< 我们的目标是什么 >

| year = 2008

Although mechanical energy is indestructible, there is a universal tendency to its dissipation, which produces throughout the system a gradual augmentation and diffusion of heat, cessation of motion and exhaustion of the potential energy of the material Universe.

虽然机械能是坚不可摧的，但是它的耗散有一种普遍的趋势，这种趋势使整个系统产生热量的逐渐增加和扩散、运动停止和物质宇宙的势能耗尽。

}}</ref>。也就是说，宇宙在很长一段时间后会冷却到很低的温度保持平衡。

—Thomson, William. [http://zapatopi.net/kelvin/papers/on_the_age_of_the_suns_heat.html On the Age of the Sun’s Heat] Macmillan's Magazine, 5 March 1862, pp. 388–93

ー汤姆森，威廉。论太阳热能的年龄 http://zapatopi.net/kelvin/papers/on_the_age_of_the_suns_heat.html 麦克米伦杂志，1862年3月5日，388–93页

The hypothesis of heat death stems from the ideas of [[William Thomson, 1st Baron Kelvin|Lord Kelvin]], who in the 1850s took the [[theory of heat]] as [[mechanical energy]] loss in nature (as embodied in the first two [[laws of thermodynamics]]) and [[Extrapolation|extrapolated]] it to larger processes on a universal scale.

The exponential acceleration of baryons' evaporation has been described by Arthur Eddington:

重子蒸发的指数加速已经被亚瑟·爱丁顿描述过了:

==Concept==

<blockquote>

< 我们的目标是什么 >

The concept of the heat death of the universe is based on the observation that the gravitational potential energy of the universe, also known as [[rest mass]] that is stored mostly in [[baryon]]s, self‑gravitationally shrinks and heats up to ever higher temperatures. Consequently, the ever‑smaller and ever‑hotter baryons "evaporate", with an exponential acceleration, into the seemingly expanding ambient space as photons, so that eventually the universe will consist of zero‑frequency photons:

All change is relative. The universe is expanding relatively to our common material standards; our material standards are shrinking relatively to the size of the universe. The theory of the "expanding universe" might also be called the theory of the "shrinking atom". <...>

所有的变化都是相对的。宇宙相对于我们共同的物质标准正在扩张; 我们的物质标准相对于宇宙的大小正在缩小。“膨胀宇宙”理论也可以称为“收缩原子”理论。我不知道你在说什么

<blockquote>

Let us then take the whole universe as our standard of constancy, and adopt the view of a cosmic being whose body is composed of intergalactic spaces and swells as they swell. Or rather we must now say it keeps the same size, for he will not admit that it is he who has changed. Watching us for a few thousand million years, he sees us shrinking; atoms, animals, planets, even the galaxies, all shrink alike; only the intergalactic spaces remain the same. The earth spirals round the sun in an ever‑decreasing orbit. It would be absurd to treat its changing revolution as a constant unit of time. The cosmic being will naturally relate his units of length and time so that the velocity of light remains constant. Our years will then decrease in geometrical progression in the cosmic scale of time. On that scale man's life is becoming briefer; his threescore years and ten are an ever‑decreasing allowance. Owing to the property of geometrical progressions an infinite number of our years will add up to a finite cosmic time; so that what we should call the end of eternity is an ordinary finite date in the cosmic calendar. But on that date the universe has expanded to infinity in our reckoning, and we have shrunk to nothing in the reckoning of the cosmic being.

那么，让我们以整个宇宙作为恒常的标准，采纳宇宙存在的观点，认为宇宙存在的身体是由星系间的空间组成的，膨胀时会膨胀。或者更确切地说，我们现在必须说它保持了同样的规模，因为他不会承认是他改变了。观察我们几千万年，他看到我们在缩小; 原子、动物、行星，甚至星系，都一样缩小; 只有星系间的空间保持不变。地球绕着太阳旋转，轨道越来越小。把它不断变化的革命当作一个固定的时间单位是荒谬的。宇宙存在自然而然地将他的长度和时间单位联系起来，以便光速保持不变。我们的年龄将随着宇宙时间尺度上的几何级数而减少。在这个尺度上，人的生命变得越来越短暂; 他的六十岁和十岁是一个不断减少的零用钱。由于几何级数的性质，我们的无限年数加起来就是一个有限的宇宙时间; 所以我们应该称之为永恆的终结时间是宇宙日历中的一个普通的有限日期。但是在那一天，宇宙在我们的推算中已经膨胀到无穷大，而我们在宇宙存在的推算中已经缩小到什么也没有。(只提供英文版本)

If the rest mass decreases by Δ''m''0, the kinetic energy ''E'' = ''c''2Δ''m''0 is produced. The same thing is true if we replace production of kinetic energy ''E'' by production of radiant energy ''E''. Continuing this line of argument, one can envisage the possibility that the whole rest mass ''m'' of a body could be converted into energy. Then the energy ''E'' = ''m''0''c''2 would be produced and the whole rest mass of the body would disappear.

We walk the stage of life, performers of a drama for the benefit of the cosmic spectator. As the scenes proceed he notices that the actors are growing smaller and the action quicker. When the last act opens the curtain rises on midget actors rushing through their parts at frantic speed. Smaller and smaller. Faster and faster. One last microscopic blurr of intense agitation. And then nothing.

我们行走在生命的舞台上，为了宇宙旁观者的利益而表演戏剧。随着场景的进行，他注意到演员们变得越来越小，动作也越来越快。当最后一幕开始时，幕布升起，侏儒演员以疯狂的速度冲过他们的角色。越来越小。越来越快。强烈搅动的最后一个微小的冲口。然后什么也没有。

:—[https://dokumen.pub/qdownload/international-encyclopedia-of-unified-science-vol-1-nos-6-10.html International Encyclopedia of Unified Science] Vol. 1, nos. 6–10, University of Chicago Press, 1955, p. 460

—Eddington, Arthur. [https://archive.org/details/in.ernet.dli.2015.220736/page/n105/mode/2up The Expanding Universe] CUP, 1933, pp. 90–92

—Eddington, Arthur.1933年， https://archive.org/details/in.ernet.dli.2015.220736/page/n105/mode/2up 90-92页

</blockquote>

</blockquote>

<blockquote>

Although mechanical energy is indestructible, there is a universal tendency to its dissipation, which produces throughout the system a gradual augmentation and diffusion of heat, cessation of motion and '''exhaustion of the potential energy of the material Universe'''.

After the evaporation of all baryons, the resultant bath of zero‑frequency photons, indistinguishable from empty space, will condense into new protons, each miles across, which will undergo another 13.8‑billion‑year‑long exponentially accelerating shrinkage and evaporation. And so ad infinitum:

在所有重子蒸发之后，由此产生的频率为0的光子浴---- 与空空难以分辨---- 将凝结成新的质子，每英里宽，这将经历另一个13.8亿的长指数加速收缩和蒸发。所以永无止境:

:—Thomson, William. [http://zapatopi.net/kelvin/papers/on_the_age_of_the_suns_heat.html On the Age of the Sun’s Heat] ''Macmillan's Magazine'', 5 March 1862, pp. 388–93

<blockquote>

< 我们的目标是什么 >

</blockquote>

According to the standard view, dark energy will lead the universe into an eternal accelerating expansion. Every bit of matter will eventually lose contact with every other bit. "It all just seemed unbelievably boring to me," Penrose says. Then he found something interesting within it: at the very end of the universe, the only remaining particles will be massless. That means everything that exists will travel at the speed of light, making the flow of time meaningless. After a few mathematical manipulations of infinity, out popped a never‑ending universe, where new big bangs are the inevitable result of a universe's demise. In Penrose's theory, one cosmos leads to another. "I used to call it a crazy scheme, but I'm starting to believe it now," he says.

根据标准观点，暗能量将导致宇宙进入永恒的加速膨胀。每一点物质最终都会与其他每一点失去联系。彭罗斯说: “对我来说，这一切都令人难以置信地无聊。”。然后他在其中发现了一些有趣的东西: 在宇宙的尽头，仅存的粒子将是无质量的。这意味着所有存在的事物都将以光速传播，使得时间的流动变得毫无意义。经过一些数学上的无限操作，一个永远不会结束的宇宙出现了，新的宇宙大爆炸是宇宙灭亡的必然结果。在彭罗斯的理论中，一个宇宙导致另一个宇宙。“我过去常说这是一个疯狂的计划，但现在我开始相信了，”他说。

—Brooks, Michael. [https://web.archive.org/web/20160413033955/http:/www.newscientist.com/article/mg20527511-300-roger-penrose-non-stop-cosmos-non-stop-career/ Roger Penrose: Non-stop cosmos, non-stop career] New Scientist, 10 March 2010

ー布鲁克斯，迈克尔。Https://web.archive.org/web/20160413033955/http:/www.newscientist.com/article/mg20527511-300-Roger-Penrose-Non-stop-cosmos-Non-stop-career/ : 《新科学家》，2010年3月10日

The exponential acceleration of [[baryon]]s' evaporation has been described by [[Arthur Eddington]]:

</blockquote>

<blockquote>

All change is relative. The universe is expanding relatively to our common material standards; our material standards are shrinking relatively to the size of the universe. The theory of the "expanding universe" might also be called the theory of the "shrinking atom". <...>

Let us then take the whole universe as our standard of constancy, and adopt the view of a cosmic being whose body is composed of intergalactic spaces and swells as they swell. Or rather we must now say it keeps the same size, for he will not admit that it is he who has changed. Watching us for a few thousand million years, he sees us shrinking; atoms, animals, planets, even the galaxies, all shrink alike; only the intergalactic spaces remain the same. The earth spirals round the sun in an ever‑decreasing orbit. It would be absurd to treat its changing revolution as a constant unit of time. The cosmic being will naturally relate his units of length and time so that the velocity of light remains constant. Our years will then decrease in geometrical progression in the cosmic scale of time. On that scale man's life is becoming briefer; his threescore years and ten are an ever‑decreasing allowance. Owing to the property of geometrical progressions an infinite number of our years will add up to a finite cosmic time; so that what we should call the end of eternity is an ordinary finite date in the cosmic calendar. But on that date the universe has expanded to infinity in our reckoning, and we have shrunk to nothing in the reckoning of the cosmic being.

The idea of heat death stems from the second law of thermodynamics, of which one version states that entropy tends to increase in an isolated system. From this, the hypothesis implies that if the universe lasts for a sufficient time, it will asymptotically approach a state where all energy is evenly distributed. In other words, according to this hypothesis, there is a tendency in nature to the dissipation (energy transformation) of mechanical energy (motion) into thermal energy; hence, by extrapolation, there exists the view that, in time, the mechanical movement of the universe will run down as work is converted to heat because of the second law.

热死的概念来源于热力学第二定律，其中一种说法认为，在一个孤立的系统中，熵倾向于增加。由此，该假设暗示，如果宇宙持续足够长的时间，它将渐近地接近所有能量均匀分布的状态。换句话说，根据这一假设，在自然界中存在着将机械能(运动)耗散(能量转换)为热能的趋势; 因此，通过外推，存在着这样一种观点，即随着时间的推移，宇宙的机械运动将减少，因为根据第二定律，功转换为热。

'''We walk the stage of life, performers of a drama for the benefit of the cosmic spectator. As the scenes proceed he notices that the actors are growing smaller and the action quicker. When the last act opens the curtain rises on midget actors rushing through their parts at frantic speed. Smaller and smaller. Faster and faster. One last microscopic blurr of intense agitation. And then nothing.'''

:—Eddington, Arthur. [https://archive.org/details/in.ernet.dli.2015.220736/page/n105/mode/2up The Expanding Universe] CUP, 1933, pp. 90–92

The conjecture that all bodies in the universe cool off, eventually becoming too cold to support life, seems to have been first put forward by the French astronomer Jean Sylvain Bailly in 1777 in his writings on the history of astronomy and in the ensuing correspondence with Voltaire. In Bailly's view, all planets have an internal heat and are now at some particular stage of cooling. Jupiter, for instance, is still too hot for life to arise there for thousands of years, while the Moon is already too cold. The final state, in this view, is described as one of "equilibrium" in which all motion ceases.

宇宙中的所有物体都会冷却，最终变得太冷以至于无法维持生命，这一猜想似乎最早是由法国天文学家让·西尔万·巴伊于1777年在他关于天文学史的著作中以及随后与伏尔泰的通信中提出的。在贝利看来，所有的行星都有内部热量，现在正处于某个特定的冷却阶段。例如，木星仍然太热，几千年来无法形成生命，而月球已经太冷了。在这种观点中，最终状态被描述为一种“平衡” ，在这种平衡中，所有的运动都停止了。

</blockquote>

The idea of heat death as a consequence of the laws of thermodynamics, however, was first proposed in loose terms beginning in 1851 by Lord Kelvin (William Thomson), who theorized further on the mechanical energy loss views of Sadi Carnot (1824), James Joule (1843) and Rudolf Clausius (1850). Thomson's views were then elaborated over the next decade by Hermann von Helmholtz and William Rankine.

然而，热死作为热力学定律的后果的想法最早是在1851年由开尔文勋爵(William Thomson)以宽松的术语提出的，他进一步从萨迪 · 卡诺(1824年)、詹姆斯 · 朱尔(1843年)和鲁道夫 · 克劳修斯(1850年)的机械能损失观点进行理论化。在接下来的十年里，赫尔曼·冯·亥姆霍兹和威廉 · 兰金详细阐述了汤姆森的观点。

After the evaporation of all [[baryon]]s, the resultant bath of zero‑frequency photons, indistinguishable from empty space, will condense into new [[proton]]s, each miles across, which will undergo another 13.8‑billion‑year‑long exponentially accelerating shrinkage and evaporation. And so ''ad infinitum'':

<blockquote>

According to the standard view, dark energy will lead the universe into an eternal accelerating expansion. Every bit of matter will eventually lose contact with every other bit. "It all just seemed unbelievably boring to me," Penrose says. Then he found something interesting within it: '''at the very end of the universe, the only remaining particles will be massless. That means everything that exists will travel at the speed of light, making the flow of time meaningless.''' After a few mathematical manipulations of infinity, out popped a never‑ending universe, where new big bangs are the inevitable result of a universe's demise. In Penrose's theory, one cosmos leads to another. "I used to call it a crazy scheme, but I'm starting to believe it now," he says.

The idea of heat death of the universe derives from discussion of the application of the first two laws of thermodynamics to universal processes. Specifically, in 1851, Lord Kelvin outlined the view, as based on recent experiments on the dynamical theory of heat: "heat is not a substance, but a dynamical form of mechanical effect, we perceive that there must be an equivalence between mechanical work and heat, as between cause and effect."

宇宙热死的概念来源于前两个热力学定律对宇宙过程的应用的讨论。特别是在1851年，开尔文勋爵根据最近关于热力学理论的实验概述了这一观点: “热不是一种物质，而是一种机械效应的动力形式，我们认为机械功和热之间，如因果之间，必然存在等价关系。”

:—Brooks, Michael. [https://web.archive.org/web/20160413033955/http:/www.newscientist.com/article/mg20527511-300-roger-penrose-non-stop-cosmos-non-stop-career/ Roger Penrose: Non-stop cosmos, non-stop career] ''New Scientist'', 10 March 2010

Lord Kelvin originated the idea of universal heat death in 1852.]]

开尔文爵士在1852年提出了宇宙热死的概念

</blockquote>

In 1852, Thomson published On a Universal Tendency in Nature to the Dissipation of Mechanical Energy, in which he outlined the rudiments of the second law of thermodynamics summarized by the view that mechanical motion and the energy used to create that motion will naturally tend to dissipate or run down. The ideas in this paper, in relation to their application to the age of the Sun and the dynamics of the universal operation, attracted the likes of William Rankine and Hermann von Helmholtz. The three of them were said to have exchanged ideas on this subject. In 1862, Thomson published "On the age of the Sun's heat", an article in which he reiterated his fundamental beliefs in the indestructibility of energy (the first law) and the universal dissipation of energy (the second law), leading to diffusion of heat, cessation of useful motion (work), and exhaustion of potential energy through the material universe, while clarifying his view of the consequences for the universe as a whole. Thomson wrote:

1852年，Thomson 出版了《论自然界中机械能耗散的普遍趋势》一书，其中他概述了热力学第二定律的基本原理，总结为机械运动和用来产生运动的能量会自然地趋于消散或下降。这篇论文中的观点，关于它们在太阳时代和宇宙运行动力学中的应用，吸引了像 William Rankine 和赫尔曼·冯·亥姆霍兹。据说他们三人就这个问题交换了意见。1862年，汤姆森发表了《论太阳热的年龄》一文，重申了他对能量不可毁灭(第一定律)和能量普遍耗散(第二定律)的基本信念，导致热量扩散、有用运动(功)停止以及通过物质宇宙的势能耗尽，同时澄清了他对整个宇宙的后果的看法。汤姆森写道:

==Origins of the idea==

The idea of heat death stems from the [[second law of thermodynamics]], of which one version states that entropy tends to increase in an [[isolated system]]. From this, the hypothesis implies that if the universe lasts for a sufficient time, it will [[asymptotically]] approach a state where all [[energy]] is evenly distributed. In other words, according to this hypothesis, there is a tendency in nature to the [[dissipation]] (energy transformation) of [[mechanical energy]] (motion) into [[thermal energy]]; hence, by extrapolation, there exists the view that, in time, the mechanical movement of the universe will run down as work is converted to heat because of the second law.

<blockquote>The result would inevitably be a state of universal rest and death, if the universe were finite and left to obey existing laws. But it is impossible to conceive a limit to the extent of matter in the universe; and therefore science points rather to an endless progress, through an endless space, of action involving the transformation of potential energy into palpable motion and hence into heat, than to a single finite mechanism, running down like a clock, and stopping for ever.</blockquote>

如果宇宙是有限的，并且遵循现有的法则，那么结果将不可避免地是宇宙的休息和死亡的状态。但是，我们不可能设想宇宙中物质范围的极限; 因此，科学指向的是一个无止境的进步，通过一个无止境的空间，将势能转化为可触知的运动，进而转化为热量，而不是一个单一的有限机制，像时钟一样慢下来，永远停止。</blockquote >

The conjecture that all bodies in the universe cool off, eventually becoming too cold to support life, seems to have been first put forward by the French astronomer [[Jean Sylvain Bailly]] in 1777 in his writings on the history of astronomy and in the ensuing correspondence with [[Voltaire]]. In Bailly's view, all planets have an [[Internal heating|internal heat]] and are now at some particular stage of cooling. [[Jupiter]], for instance, is still too hot for life to arise there for thousands of years, while the [[Moon]] is already too cold. The final state, in this view, is described as one of "equilibrium" in which all motion ceases.<ref>
In the years to follow both Thomson's 1852 and the 1862 papers, Helmholtz and Rankine both credited Thomson with the idea, but read further into his papers by publishing views stating that Thomson argued that the universe will end in a "heat death" (Helmholtz) which will be the "end of all physical phenomena" (Rankine).

在汤姆森1852年和1862年的论文发表后的几年里，亥姆霍兹和兰金都赞扬了汤姆森的这个想法，但他们对汤姆森的论文进行了进一步的解读，发表了自己的观点，认为汤姆森认为宇宙将以“热死亡”(亥姆霍兹)结束，这将是“所有物理现象的终结”(兰金)。

{{Cite book

|title = A History of Modern Planetary Physics: Nebulous Earth

|last = Brush

|first = Stephen G.

Proposals about the final state of the universe depend on the assumptions made about its ultimate fate, and these assumptions have varied considerably over the late 20th century and early 21st century. In a hypothesized "open" or "flat" universe that continues expanding indefinitely, either a heat death or a Big Rip is expected to eventually occur.

关于宇宙最终状态的提议取决于对宇宙最终命运的假设，而这些假设在20世纪晚期和21世纪早期已经发生了相当大的变化。在一个假设的“开放”或“平坦”宇宙，继续膨胀无限期，要么热死或大撕裂预计最终发生。

|author-link = Stephen G. Brush

|publisher = Cambridge University Press

If a Big Rip does not happen long before that, the "heat death" situation could be avoided if there is a method or mechanism to regenerate hydrogen atoms from radiation, dark matter, dark energy, zero-point energy, or other sources. If so, it is at least possible that star formation and heat transfer can continue, avoiding a gradual running down of the universe due to the conversion of matter into energy and heavier elements in stellar processes, and the absorption of matter by black holes and their subsequent evaporation as Hawking radiation.

如果大裂缝不会在那之前很久发生，那么如果有一种方法或机制可以从辐射、暗物质、暗能量、零点能量或其他来源再生氢原子，那么“热死”情况就可以避免。如果是这样的话，至少恒星的形成和热量传递可以继续下去，从而避免了在恒星形成过程中由于物质转化为能量和更重的元素，以及黑洞吸收物质并随之蒸发为霍金辐射而导致的宇宙的逐渐减少。

|year = 1996

|isbn = 978-0-521-44171-1

|volume = 1

|page = [https://archive.org/details/historyofmodernp0000brus/page/77 77]

|url = https://archive.org/details/historyofmodernp0000brus/page/77

From the Big Bang through the present day, matter and dark matter in the universe are thought to have been concentrated in stars, galaxies, and galaxy clusters, and are presumed to continue to do so well into the future. Therefore, the universe is not in thermodynamic equilibrium, and objects can do physical work.:§VID The decay time for a supermassive black hole of roughly 1 galaxy mass (1011 solar masses) due to Hawking radiation is on the order of 10100 years, so entropy can be produced until at least that time. Some large black holes in the universe are predicted to continue to grow up to perhaps 1014 during the collapse of superclusters of galaxies. Even these would evaporate over a timescale of up to 10106 years. After that time, the universe enters the so-called Dark Era and is expected to consist chiefly of a dilute gas of photons and leptons. Over vast periods of time, a spontaneous entropy decrease would eventually occur via the Poincaré recurrence theorem, thermal fluctuations, and fluctuation theorem. Such a scenario, however, has been described as "highly speculative, probably wrong, [and] completely untestable". Sean M. Carroll, originally an advocate of this idea, no longer supports it.

从大爆炸到现在，宇宙中的物质和暗物质被认为集中在恒星、星系和星系团中，并且被认为在未来会继续这样做。因此，宇宙不在热力学平衡，物体可以做物理工作。一个大约有1个星系质量(10个 11个 太阳质量)的超重黑洞，由于霍金辐射的存在，其衰变时间大约为10 100 年，因此至少在那个时间之前，熵是可以产生的。据预测，在超星系团坍缩期间，宇宙中的一些大型黑洞可能会继续增长到10个。即使这些也会在长达10年的时间内蒸发掉。在那之后，宇宙进入了所谓的黑暗时期，预计主要由光子和轻子组成的稀释气体。在大量的时间里，自发的熵减少最终会通过庞加莱始态复现定理、热涨落和涨落定理发生。然而，这种情况被描述为“高度投机，可能是错误的，并且完全不可测试”。最初支持这一观点的肖恩 · m · 卡罗尔不再支持这一观点。

}}</ref>

The idea of heat death as a consequence of the laws of thermodynamics, however, was first proposed in loose terms beginning in 1851 by Lord Kelvin (William Thomson), who theorized further on the mechanical energy loss views of [[Nicolas Léonard Sadi Carnot|Sadi Carnot]] (1824), [[James Joule]] (1843) and [[Rudolf Clausius]] (1850). Thomson's views were then elaborated over the next decade by [[Hermann von Helmholtz]] and [[William Rankine]].{{citation needed|date=November 2015}}

Max Planck wrote that the phrase "entropy of the universe" has no meaning because it admits of no accurate definition. More recently, Walter Grandy writes: "It is rather presumptuous to speak of the entropy of a universe about which we still understand so little, and we wonder how one might define thermodynamic entropy for a universe and its major constituents that have never been in equilibrium in their entire existence." According to Tisza: "If an isolated system is not in equilibrium, we cannot associate an entropy with it." Buchdahl writes of "the entirely unjustifiable assumption that the universe can be treated as a closed thermodynamic system". According to Gallavotti: "... there is no universally accepted notion of entropy for systems out of equilibrium, even when in a stationary state." Discussing the question of entropy for non-equilibrium states in general, Lieb and Yngvason express their opinion as follows: "Despite the fact that most physicists believe in such a nonequilibrium entropy, it has so far proved impossible to define it in a clearly satisfactory way." In Landsberg's opinion: "The third misconception is that thermodynamics, and in particular, the concept of entropy, can without further enquiry be applied to the whole universe. ... These questions have a certain fascination, but the answers are speculations, and lie beyond the scope of this book."

马克斯 · 普朗克写道，“宇宙的熵”这个短语没有任何意义，因为它不承认有准确的定义。最近，Walter Grandy 写道: “我们仍然对宇宙的熵知之甚少，我们想知道如何定义一个宇宙及其主要成分的熵，而这些成分在整个存在过程中从未处于平衡状态。”蒂萨说: “如果一个孤立的系统不处于平衡状态，我们就不能把熵和它联系起来。”布赫达尔写道: “宇宙可以被视为一个封闭的热力学系统，这是完全不合理的假设。”。根据 Gallavotti 的说法: “对于失去平衡的系统，没有普遍接受的熵的概念，即使是在定态中。”在讨论一般非平衡态的熵问题时，Lieb 和 Yngvason 表达了他们的观点如下: “尽管大多数物理学家相信存在这样的非平衡熵，但迄今为止已经证明不可能以一种明显令人满意的方式来定义它。”兰兹伯格认为: “第三个误解是，热力学，特别是熵的概念，不需要进一步探究就可以应用于整个宇宙。...这些问题有一定的吸引力，但答案都是推测，超出了本书的范围。”

===History===

A 2010 analysis of entropy states, "The entropy of a general gravitational field is still not known", and "gravitational entropy is difficult to quantify". The analysis considers several possible assumptions that would be needed for estimates and suggests that the observable universe has more entropy than previously thought. This is because the analysis concludes that supermassive black holes are the largest contributor. Lee Smolin goes further: "It has long been known that gravity is important for keeping the universe out of thermal equilibrium. Gravitationally bound systems have negative specific heat—that is, the velocities of their components increase when energy is removed. ... Such a system does not evolve toward a homogeneous equilibrium state. Instead it becomes increasingly structured and heterogeneous as it fragments into subsystems."

2010年对熵状态的分析表明，“一个普通引力场的熵仍然不为人知” ，“引力熵很难量化”。该分析考虑了几个可能的假设，这些假设对于估计来说是必要的，并且表明可观测宇宙的熵比之前想象的要多。这是因为分析得出结论，超大质量黑洞是最大的贡献者。李 · 斯莫林更进一步说: “人们早就知道，引力对于防止宇宙进入热平衡十分重要。引力束缚系统具有负的比热，也就是说，当能量消失时，其组分的速度增加。...这样的系统不会演化到均匀的平衡状态。相反，随着它分解成子系统，它变得越来越结构化和异构化。”

The idea of heat death of the universe derives from discussion of the application of the first two laws of thermodynamics to universal processes. Specifically, in 1851, Lord Kelvin outlined the view, as based on recent experiments on the dynamical [[theory of heat]]: "heat is not a substance, but a dynamical form of mechanical effect, we perceive that there must be an equivalence between mechanical work and heat, as between cause and effect."<ref>Thomson, Sir William. (1851). [https://zapatopi.net/kelvin/papers/on_the_dynamical_theory_of_heat.html "On the Dynamical Theory of Heat, with numerical results deduced from Mr Joule’s equivalent of a Thermal Unit, and M. Regnault’s Observations on Steam"] Excerpts. [§§1–14 & §§99–100], ''[[Transactions of the Royal Society of Edinburgh]]'', March 1851, and ''[[Philosophical Magazine|Philosophical Magazine IV]]'', 1852. [from ''Mathematical and Physical Papers'', vol. i, art. XLVIII, pp. 174]</ref>

This point of view is also supported by the fact of a recent experimental discovery of a stable non-equilibrium steady state in a relatively simple closed system. It should be expected that an isolated system fragmented into subsystems does not necessarily come to thermodynamic equilibrium and remain in non-equilibrium steady state. Entropy will be transmitted from one subsystem to another, but its production will be zero, which does not contradict the second law of thermodynamics.

最近在一个相对简单的封闭系统中实验发现了稳定的非平衡稳态，这也支持了这一观点。可以预期的是，一个分裂成子系统的孤立系统不一定会达到热力学平衡并保持非平衡的稳定状态。熵将从一个子系统传递到另一个子系统，但是它的产出将为零，这与热力学第二定律并不矛盾。

[[Image:Lord Kelvin photograph.jpg|175px|right|thumb|[[William Thomson, 1st Baron Kelvin|Lord Kelvin]] originated the idea of universal heat death in 1852.|链接=Special:FilePath/Lord_Kelvin_photograph.jpg]]

In 1852, Thomson published ''On a Universal Tendency in Nature to the Dissipation of Mechanical Energy'', in which he outlined the rudiments of the second law of thermodynamics summarized by the view that mechanical motion and the energy used to create that motion will naturally tend to dissipate or run down.<ref>Thomson, Sir William (1852). [https://zapatopi.net/kelvin/papers/on_a_universal_tendency.html "On a Universal Tendency in Nature to the Dissipation of Mechanical Energy"] ''[[Proceedings of the Royal Society of Edinburgh]]'' for 19 April 1852, also ''[[Philosophical Magazine]]'', Oct. 1852. [This version from ''Mathematical and Physical Papers'', vol. i, art. 59, pp. 511.]</ref> The ideas in this paper, in relation to their application to the age of the [[Sun]] and the dynamics of the universal operation, attracted the likes of William Rankine and Hermann von Helmholtz. The three of them were said to have exchanged ideas on this subject.<ref name="Energy and Empire">
{{Cite book

| title = Energy and Empire: A Biographical Study of Lord Kelvin

| last = Smith

| first = Crosbie

| last2 = Wise

| first2 = M. Norton

| publisher = Cambridge University Press

| year = 1989

| isbn = 978-0-521-26173-9

| pages = 500

| author-link2 = M. Norton Wise

}}</ref> In 1862, Thomson published "On the age of the Sun's heat", an article in which he reiterated his fundamental beliefs in the indestructibility of energy (the [[first law of thermodynamics|first law]]) and the universal dissipation of energy (the second law), leading to diffusion of heat, cessation of useful motion ([[work (physics)|work]]), and exhaustion of [[potential energy]] through the material universe, while clarifying his view of the consequences for the universe as a whole. Thomson wrote:

<blockquote>The result would inevitably be a state of universal rest and death, if the universe were finite and left to obey existing laws. But it is impossible to conceive a limit to the extent of matter in the universe; and therefore science points rather to an endless progress, through an endless space, of action involving the transformation of [[potential energy]] into [[Work (physics)|palpable motion]] and hence into [[heat]], than to a single finite mechanism, running down like a clock, and stopping for ever.<ref>

{{Cite magazine

| last = Thomson

| first = Sir William

| date = 5 March 1862

| title = On the Age of the Sun's Heat

| url = https://zapatopi.net/kelvin/papers/on_the_age_of_the_suns_heat.html

| magazine = [[Macmillan's Magazine]]

| volume = 5

| pages = 388–93

}}</ref></blockquote>

Category:Physical cosmology

类别: 物理宇宙学

In the years to follow both Thomson's 1852 and the 1862 papers, Helmholtz and Rankine both credited Thomson with the idea, but read further into his papers by publishing views stating that Thomson argued that the universe will end in a "''heat death''" (Helmholtz) which will be the "''end of all physical phenomena''" (Rankine).<ref name="Energy and Empire" /><ref>

Category:Thermodynamic entropy

类别: 熵

{{Cite web

Category:Doomsday scenarios

分类: 末日情景

| url = http://webplaza.pt.lu/fklaess/html/HISTORIA.HTML

Category:1851 in science

类别: 1851年的科学

| title = Physics Chronology

Category:Ultimate fate of the universe

类别: 宇宙的终极命运

<noinclude>

This page was moved from [[wikipedia:en:Heat death of the universe]]. Its edit history can be viewed at [[热寂/edithistory]]</noinclude>

[[Category:待整理页面]]

韦斯特方程

2021-09-09T13:29:29Z

Fernando：格式小修，定稿

此词条暂由彩云小译翻译，由Fernando审校。

'''西尔韦斯特方程'''是控制论中的矩阵方程，形式如下<ref>这个方程也有常见的等价形式 ''AX'' − ''XB'' = ''C''.</ref>:

<math>A X + X B = C.</math>

其中''A''，''B''，''C''为已知的矩阵，问题是要找到能够满足方程的矩阵X。所有矩阵的系数都是复数。为了使方程有意义，矩阵的行和列需要满足一定条件，''A'' 和 ''B'' 都要是方阵，大小分别是''n''和''m''，而''X''和''C''要是''n x'' ''m''列的矩阵，''n''和''m''也可以相等，四个矩阵都是大小相同的方阵。

当且仅当 ''A'' 和-''b'' 没有共同的本征值时，西尔韦斯特有唯一解 ''X'' 。更一般地，方程 <math>A X + X B = C.</math> 也可以视为(可能无限维中)巴拿赫空间中有界算子的方程。在这种情况下，此情形下，有唯一解 ''X'' 的充分必要条件几乎相同: ''A'' 和-''B'' 的谱不相交<ref>Bhatia and Rosenthal, 1997</ref>。

==解的存在及唯一==

利用克罗内克积符号和向量化算子操作符<math>\operatorname{vec}</math>，我们可以以下形式重写韦斯特方程:
:<math> (I_m \otimes A + B^T \otimes I_n) \operatorname{vec}X = \operatorname{vec}C,</math>
其中 ''A'' 是 ''n'' ''×'' ''m''的矩阵，''B'' 是''m'' ''×'' ''m''的矩阵，''X'' 是''n'' ''×'' ''m''的矩阵，<math>I_k</math> 是 <math>k \times k</math>的单位矩阵。在这种形式下，该方程可以看作是一个大小为<math>mn \times mn</math>的线性系统<ref>然而，不建议为了数值解重写这种形式的方程，因为这个版本计算代价较高，并且存在病态。</ref>。然而，不建议为了数值解重写这种形式的方程，因为这个版本计算代价较高，并且存在病态。

'''定理'''。给定矩阵 <math>A\in \mathbb{C}^{n\times n}</math>和<math>B\in \mathbb{C}^{m\times m}</math>，韦斯特方程 <math>AX+XB=C</math>对任意 <math>C\in\mathbb{C}^{n\times m}</math>有唯一解 ''X'' 当且仅当 ''A'' 和''-B'' 不共享任何特征值。

'''证明'''。方程<math>AX+XB=C</math>是一个m和n未知的线性系统，涉及和未知数等量的方程。因此，对于任意给定的 C，它是唯一可解的当且仅当齐次方程 <math>
AX+XB=0
</math>仅存在平凡解<math>0</math>。

(i)假设 ''A'' 和-''B'' 不共享任何特征值。设 ''X'' 是上述齐次方程的解。于是有 <math>AX=X(-B)</math>，它可以被数学归纳法提升到 <math>
A^kX = X(-B)^k
</math>
对任意 <math>k \ge 0</math>都成立。因此，对于任意多项式 p，<math>
p(A) X = X p(-B)
</math>，特别地，设 <math>p</math> 是 ''A'' 的特征多项式。那么由 Cayley-Hamilton 定理可得<math>p(A)=0</math>。同时谱映射定理告诉我们<math>
\sigma(p(-B)) = p(\sigma(-B)),
</math>，其中 <math>\sigma(\cdot)</math>表示矩阵的谱。由于 ''A'' 和-''B'' 不共享任何特征值，<math>p(\sigma(-B))</math>不包含零，因此 <math>p(-B)</math>是非奇异的。从而得到<math>X= 0</math>。这证明了定理的“当”部分。

(ii)现在假设 ''A'' 和-''B'' 有一个相同的特征值 λ。设 u 是 ''A'' 的对应右特征向量，v 是-''B'' 的对应左特征向量，并且 <math>X=u{v}^*</math>。于是<math>X\neq 0</math>，而<math>
AX+XB = A(uv^*)-(uv^*)(-B) = \lambda uv^*-\lambda uv^* = 0.
</math>。因此，''X'' 是上述齐次方程的非平凡解。这证明了定理的“仅当”部分得证。

'''Q.E.D.'''

作为谱映射定理的另一种形式，证明的第(i)部分<math>p(-B)</math>的非奇异性也可以用贝祖特的互素多项式恒等式来证明。设 q 是-''B'' 的特征多项式。由于 ''A'' 和-''B'' 不共享任何特征值，所以 p 和 q 互素。因此存在多项式 f 和 g，使得 <math>p(z)f(z)+q(z)g(z)\equiv 1</math>。利用 Cayley-Hamilton 定理，可得<math>q(-B)=0</math>，这意味着 <math>p(-B)</math>是非奇异的。

这个定理对实矩阵仍然成立，但需要注意的是考虑它们的复特征值。充分条件的证明仍然适用; 对于必要条件的证明，请注意 <math>\mathrm{Re}(uv^*)</math>和 <math>\mathrm{Im}(uv^*)</math> 都满足齐次方程 ''AX + XB = 0''，而它们不能同时为零。

=Roth消去法则=

给定两个大小分别为''n'' 和 ''m'' 的复方阵 ''A'' 和 ''B''，以及大小为 ''n × m'' 的矩阵 ''C''，我们可以确认下列两个大小为 ''n + m'' 的方阵[math]\begin{bmatrix} A & C \\ 0 & B \end{bmatrix}[/math]和[math]\begin{bmatrix} A & 0 \\0&B \end{bmatrix}[/math]是否相似。当存在矩阵 ''X'' 使得 ''AX-XB'' ''='' ''C'' ，这两个矩阵就是相似的。换句话说，''X'' 是维斯特方程的解。这就是众所周知的'''Roth消去法则'''<ref>{{cite journal|last1=Gerrish|first1=F|last2=Ward|first2=A.G.B|title=Sylvester's matrix equation and Roth's removal rule|journal=The Mathematical Gazette|date=Nov 1998|volume=82|issue=495|pages=423–430|doi=10.2307/3619888|jstor=3619888}}</ref>。

一种简便的检查方式如下：如果''AX-XB = C''，那么：

<math>\begin{bmatrix}I_n & X \\ 0 & I_m \end{bmatrix} \begin{bmatrix} A&C\\0&B \end{bmatrix} \begin{bmatrix} I_n & -X \\ 0& I_m \end{bmatrix} = \begin{bmatrix} A&0\\0&B \end{bmatrix}.</math>

Roth消去法则无法一般化到巴拿赫空间中的无穷维有界算子中。<ref>Bhatia and Rosenthal, p.3</ref>
==数值解==
韦斯特方程数值解的一个经典算法是 Bartels-Stewart 算法，该算法通过 QR 算法将矩阵''A'' 和 ''B'' 转化为舒尔形式，然后通过逆向取代法求解三角矩阵。在LAPACK，或是GNU Octave的lyap函数中，该算法的计算代价是[[Big O notation|<math>\mathcal{O}(n^3)</math>]]<ref>{{Cite web | url=https://octave.sourceforge.io/control/function/lyap.html | title=Function Reference: Lyap}}</ref>。也可以参阅该语言中的 sylvester 函数。自 GNU Octave Version 4.0以来，不推荐使用<code>syl</code>命令。<ref>{{Cite web | url=https://www.gnu.org/software/octave/doc/interpreter/Functions-of-a-Matrix.html | title=Functions of a Matrix (GNU Octave (version 4.4.1))}}</ref><ref>The <code>syl</code> 命令自从GNU Octave 4.0版本以后就弃用了。</ref>在某些特定的图像处理应用程序中，导出的韦斯特方程有会有解析解<ref>{{cite journal |first=Q. |last=Wei |first2=N. |last2=Dobigeon |first3=J.-Y. |last3=Tourneret |title=Fast Fusion of Multi-Band Images Based on Solving a Sylvester Equation|journal=[[IEEE Transactions on Image Processing|IEEE]] |volume=24 |year=2015 |issue=11 |pages=4109–4121 |doi=10.1109/TIP.2015.2458572|pmid=26208345 |arxiv=1502.03121|bibcode=2015ITIP...24.4109W}}</ref>。

==相关条目==
*李雅普诺夫方程
*代数Riccati方程

==脚注==
{{Reflist}}

==引用==
*{{cite journal |first=J. |last=Sylvester |title=Sur l'equations en matrices <math>px = xq</math> |journal=[[C. R. Acad. Sci. Paris]] |volume=99 |year=1884 |issue=2 |pages=67–71, 115–116 }}
*{{cite journal |first=R. H. |last=Bartels |first2=G. W. |last2=Stewart |title=Solution of the matrix equation <math>AX +XB = C</math> |journal=[[Comm. ACM]] |volume=15 |year=1972 |issue=9 |pages=820–826 |doi=10.1145/361573.361582 }}
*{{cite journal |first=R. |last=Bhatia |first2=P. |last2=Rosenthal |title=How and why to solve the operator equation <math>AX -XB = Y </math> ? |journal=[[Bull. London Math. Soc.]] |volume=29 |issue=1 |year=1997 |pages=1–21 |doi=10.1112/S0024609396001828 }}
*{{cite journal |first=S.-G. |last=Lee |first2=Q.-P. |last2=Vu |title=Simultaneous solutions of Sylvester equations and idempotent matrices separating the joint spectrum |journal=[[Linear Algebra and its Applications|Linear Algebra Appl.]] |volume=435 |year=2011 |issue=9 |pages=2097–2109 |doi=10.1016/j.laa.2010.09.034 |doi-access=free }}
*{{cite journal |first=Q. |last=Wei |first2=N. |last2=Dobigeon |first3=J.-Y. |last3=Tourneret |title=Fast Fusion of Multi-Band Images Based on Solving a Sylvester Equation|journal=[[IEEE Transactions on Image Processing]] |volume=24 |year=2015 |issue=11 |pages=4109–4121 |doi=10.1109/TIP.2015.2458572|arxiv=1502.03121|bibcode=2015ITIP...24.4109W |pmid=26208345}}
*{{cite book|last1=Birkhoff and MacLane|title=A survey of Modern Algebra|publisher=Macmillan|pages=213, 299}}

*
*
*
*
*
*

*

*

*

*

*

*

== 外部链接==
*[http://calculator-fx.com/calculator/linear-algebra/solve-sylvester-equation Online solver for arbitrary sized matrices.]{{deadlink|date=May 2021}}
*[http://reference.wolfram.com/mathematica/ref/LyapunovSolve.html Mathematica function to solve the Sylvester equation]
*[http://www.mathworks.co.uk/help/matlab/ref/sylvester.html MATLAB function to solve the Sylvester equation]

* Online solver for arbitrary sized matrices.
*Mathematica function to solve the Sylvester equation
*MATLAB function to solve the Sylvester equation

*任意大小矩阵的在线求解器。
* Mathematica 函数求解 Sylvester 方程
*MATLAB 函数求解 Sylvester 方程

[[Category:Matrices]]
[[Category:Control theory]]

{{Authority control}}

范畴: 矩阵范畴: 控制论

<noinclude>

This page was moved from [[wikipedia:en:Sylvester equation]]. Its edit history can be viewed at [[韦斯特方程/edithistory]]</noinclude>

[[Category:待整理页面]]

韦斯特方程

2021-09-09T09:04:23Z

Fernando：审校初稿完成

此词条暂由彩云小译翻译，由Fernando审校。

'''西尔韦斯特方程'''是控制论中的矩阵方程，形式如下<ref>这个方程也有常见的等价形式 ''AX'' − ''XB'' = ''C''.</ref>:

<math>A X + X B = C.</math>

其中''A''，''B''，''C''为已知的矩阵，问题是要找到能够满足方程的矩阵X。所有矩阵的系数都是复数。为了使方程有意义，矩阵的行和列需要满足一定条件，''A'' 和 ''B'' 都要是方阵，大小分别是''n''和''m''，而''X''和''C''要是''n''行''m''列的矩阵，''n''和''m''也可以相等，四个矩阵都是大小相同的方阵。

当且仅当 ''A'' 和-''b'' 没有共同的本征值时，西尔韦斯特有唯一解 ''X'' 。更一般地，方程 <math>A X + X B = C.</math> 也可以视为(可能无限维中)巴拿赫空间中有界算子的方程。在这种情况下，此情形下，有唯一解 ''X'' 的充分必要条件几乎相同: ''A'' 和-''B'' 的谱不相交<ref>Bhatia and Rosenthal, 1997</ref>。

==解的存在及唯一==

利用克罗内克积符号和向量化算子操作符<math>\operatorname{vec}</math>，我们可以以下形式重写韦斯特方程:
:<math> (I_m \otimes A + B^T \otimes I_n) \operatorname{vec}X = \operatorname{vec}C,</math>
其中 ''A'' 是 n × m的矩阵，''B'' 是m × m的矩阵，X 是n × m的矩阵，<math>I_k</math> 是 <math>k \times k</math>的单位矩阵。在这种形式下，该方程可以看作是一个大小为<math>mn \times mn</math>的线性系统<ref>然而，不建议为了数值解重写这种形式的方程，因为这个版本计算代价较高，并且存在病态。</ref>。然而，不建议为了数值解重写这种形式的方程，因为这个版本计算代价较高，并且存在病态。

'''定理'''。给定矩阵 <math>A\in \mathbb{C}^{n\times n}</math>和<math>B\in \mathbb{C}^{m\times m}</math>，韦斯特方程 <math>AX+XB=C</math>对任意 <math>C\in\mathbb{C}^{n\times m}</math>有唯一解 ''X'' 当且仅当 ''A'' 和''-B'' 不共享任何特征值。

'''证明'''。方程<math>AX+XB=C</math>是一个m和n未知的线性系统，涉及和未知数等量的方程。因此，对于任意给定的 C，它是唯一可解的当且仅当齐次方程 <math>
AX+XB=0
</math>仅存在平凡解<math>0</math>。

(i)假设 ''A'' 和-''B'' 不共享任何特征值。设 ''X'' 是上述齐次方程的解。于是有 <math>AX=X(-B)</math>，它可以被数学归纳法提升到 <math>
A^kX = X(-B)^k
</math>
对任意 <math>k \ge 0</math>都成立。因此，对于任意多项式 p，<math>
p(A) X = X p(-B)
</math>，特别地，设 <math>p</math> 是 ''A'' 的特征多项式。那么由 Cayley-Hamilton 定理可得<math>p(A)=0</math>。同时谱映射定理告诉我们<math>
\sigma(p(-B)) = p(\sigma(-B)),
</math>，其中 <math>\sigma(\cdot)</math>表示矩阵的谱。由于 ''A'' 和-''B'' 不共享任何特征值，<math>p(\sigma(-B))</math>不包含零，因此 <math>p(-B)</math>是非奇异的。从而得到<math>X= 0</math>。这证明了定理的“当”部分。

(ii)现在假设 ''A'' 和-''B'' 有一个相同的特征值 λ。设 u 是 ''A'' 的对应右特征向量，v 是-''B'' 的对应左特征向量，并且 <math>X=u{v}^*</math>。于是<math>X\neq 0</math>，而<math>
AX+XB = A(uv^*)-(uv^*)(-B) = \lambda uv^*-\lambda uv^* = 0.
</math>。因此，''X'' 是上述齐次方程的非平凡解。这证明了定理的“仅当”部分得证。

'''Q.E.D.'''

作为谱映射定理的另一种形式，证明的第(i)部分<math>p(-B)</math>的非奇异性也可以用贝祖特的互素多项式恒等式来证明。设 q 是-''B'' 的特征多项式。由于 ''A'' 和-''B'' 不共享任何特征值，所以 p 和 q 互素。因此存在多项式 f 和 g，使得 <math>p(z)f(z)+q(z)g(z)\equiv 1</math>。利用 Cayley-Hamilton 定理，可得<math>q(-B)=0</math>，这意味着 <math>p(-B)</math>是非奇异的。

这个定理对实矩阵仍然成立，但需要注意的是考虑它们的复特征值。充分条件的证明仍然适用; 对于必要条件的证明，请注意 <math>\mathrm{Re}(uv^*)</math>和 <math>\mathrm{Im}(uv^*)</math> 都满足齐次方程 ''AX + XB = 0''，而它们不能同时为零。

=Roth消去法则=

给定两个大小分别为''n'' 和 ''m'' 的复方阵 ''A'' 和 ''B''，以及大小为 n × m 的矩阵 ''C''，我们可以确认下列两个大小为 ''n + m'' 的方阵[math]\begin{bmatrix} A & C \\ 0 & B \end{bmatrix}[/math]和[math]\begin{bmatrix} A & 0 \\0&B \end{bmatrix}[/math]是否相似。当存在矩阵 ''X'' 使得 ''AX-XB'' ''='' ''C'' ，这两个矩阵就是相似的。换句话说，''X'' 是维斯特方程的解。这就是众所周知的'''Roth消去法则'''<ref>{{cite journal|last1=Gerrish|first1=F|last2=Ward|first2=A.G.B|title=Sylvester's matrix equation and Roth's removal rule|journal=The Mathematical Gazette|date=Nov 1998|volume=82|issue=495|pages=423–430|doi=10.2307/3619888|jstor=3619888}}</ref>。

一种简便的检查方式如下：如果''AX-XB = C''，那么：

<math>\begin{bmatrix}I_n & X \\ 0 & I_m \end{bmatrix} \begin{bmatrix} A&C\\0&B \end{bmatrix} \begin{bmatrix} I_n & -X \\ 0& I_m \end{bmatrix} = \begin{bmatrix} A&0\\0&B \end{bmatrix}.</math>

Roth消去法则无法一般化到巴拿赫空间中的无穷维有界算子中。<ref>Bhatia and Rosenthal, p.3</ref>
==数值解==
韦斯特方程数值解的一个经典算法是 Bartels-Stewart 算法，该算法通过 QR 算法将矩阵''A'' 和 ''B'' 转化为舒尔形式，然后通过逆向取代法求解三角矩阵。在LAPACK，或是GNU Octave的lyap函数中，该算法的计算代价是[[Big O notation|<math>\mathcal{O}(n^3)</math>]]<ref>{{Cite web | url=https://octave.sourceforge.io/control/function/lyap.html | title=Function Reference: Lyap}}</ref>。也可以参阅该语言中的 sylvester 函数。自 GNU Octave Version 4.0以来，不推荐使用<code>syl</code>命令。<ref>{{Cite web | url=https://www.gnu.org/software/octave/doc/interpreter/Functions-of-a-Matrix.html | title=Functions of a Matrix (GNU Octave (version 4.4.1))}}</ref><ref>The <code>syl</code> 命令自从GNU Octave 4.0版本以后就弃用了。</ref>在某些特定的图像处理应用程序中，导出的韦斯特方程有会有解析解<ref>{{cite journal |first=Q. |last=Wei |first2=N. |last2=Dobigeon |first3=J.-Y. |last3=Tourneret |title=Fast Fusion of Multi-Band Images Based on Solving a Sylvester Equation|journal=[[IEEE Transactions on Image Processing|IEEE]] |volume=24 |year=2015 |issue=11 |pages=4109–4121 |doi=10.1109/TIP.2015.2458572|pmid=26208345 |arxiv=1502.03121|bibcode=2015ITIP...24.4109W}}</ref>。

==相关条目==
*李雅普诺夫方程
*代数Riccati方程

==脚注==
{{Reflist}}

==引用==
*{{cite journal |first=J. |last=Sylvester |title=Sur l'equations en matrices <math>px = xq</math> |journal=[[C. R. Acad. Sci. Paris]] |volume=99 |year=1884 |issue=2 |pages=67–71, 115–116 }}
*{{cite journal |first=R. H. |last=Bartels |first2=G. W. |last2=Stewart |title=Solution of the matrix equation <math>AX +XB = C</math> |journal=[[Comm. ACM]] |volume=15 |year=1972 |issue=9 |pages=820–826 |doi=10.1145/361573.361582 }}
*{{cite journal |first=R. |last=Bhatia |first2=P. |last2=Rosenthal |title=How and why to solve the operator equation <math>AX -XB = Y </math> ? |journal=[[Bull. London Math. Soc.]] |volume=29 |issue=1 |year=1997 |pages=1–21 |doi=10.1112/S0024609396001828 }}
*{{cite journal |first=S.-G. |last=Lee |first2=Q.-P. |last2=Vu |title=Simultaneous solutions of Sylvester equations and idempotent matrices separating the joint spectrum |journal=[[Linear Algebra and its Applications|Linear Algebra Appl.]] |volume=435 |year=2011 |issue=9 |pages=2097–2109 |doi=10.1016/j.laa.2010.09.034 |doi-access=free }}
*{{cite journal |first=Q. |last=Wei |first2=N. |last2=Dobigeon |first3=J.-Y. |last3=Tourneret |title=Fast Fusion of Multi-Band Images Based on Solving a Sylvester Equation|journal=[[IEEE Transactions on Image Processing]] |volume=24 |year=2015 |issue=11 |pages=4109–4121 |doi=10.1109/TIP.2015.2458572|arxiv=1502.03121|bibcode=2015ITIP...24.4109W |pmid=26208345}}
*{{cite book|last1=Birkhoff and MacLane|title=A survey of Modern Algebra|publisher=Macmillan|pages=213, 299}}

*
*
*
*
*
*

*

*

*

*

*

*

== 外部链接==
*[http://calculator-fx.com/calculator/linear-algebra/solve-sylvester-equation Online solver for arbitrary sized matrices.]{{deadlink|date=May 2021}}
*[http://reference.wolfram.com/mathematica/ref/LyapunovSolve.html Mathematica function to solve the Sylvester equation]
*[http://www.mathworks.co.uk/help/matlab/ref/sylvester.html MATLAB function to solve the Sylvester equation]

* Online solver for arbitrary sized matrices.
*Mathematica function to solve the Sylvester equation
*MATLAB function to solve the Sylvester equation

*任意大小矩阵的在线求解器。
* Mathematica 函数求解 Sylvester 方程
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{{short description|The set of life-sustaining chemical transformations within the cells of organisms }}

{{redirect|Cell metabolism|the journal|Cell Metabolism}}

{{about||the architectural movement|Metabolism (architecture)}}

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[[File:Metabolism.png|thumb|细胞新陈代谢的简化图]]

[[File:ATP-3D-vdW.png|thumb|right|[[三磷酸腺苷]]的结构（ATP），它是能量代谢中的中枢中间体。]]

'''Metabolism''' ({{IPAc-en|m|ə|ˈ|t|æ|b|ə|l|ɪ|z|ə|m}}, from {{lang-el|μεταβολή}} ''metabolē'', "change") is the set of [[life]]-sustaining [[chemical reactions]] in [[organisms]]. The three main purposes of metabolism are: the conversion of food to [[energy]] to run cellular processes; the conversion of food/fuel to building blocks for [[protein]]s, [[lipid]]s, [[nucleic acid]]s, and some [[carbohydrate]]s; and the elimination of [[Metabolic waste|metabolic wastes]]. These [[enzyme]]-catalyzed reactions allow organisms to grow and reproduce, maintain their structures, and respond to their environments. (The word metabolism can also refer to the sum of all chemical reactions that occur in living organisms, including [[digestion]] and the transport of substances into and between different cells, in which case the above described set of reactions within the cells is called intermediary metabolism or intermediate metabolism).

Metabolism (/məˈtæbəlɪzəm/, from Greek: μεταβολή metabolē, "change") is the set of life-sustaining chemical reactions in organisms. The three main purposes of metabolism are: the conversion of food to energy to run cellular processes; the conversion of food/fuel to building blocks for proteins, lipids, nucleic acids, and some carbohydrates; and the elimination of metabolic wastes. These enzyme-catalyzed reactions allow organisms to grow and reproduce, maintain their structures, and respond to their environments. (The word metabolism can also refer to the sum of all chemical reactions that occur in living organisms, including digestion and the transport of substances into and between different cells, in which case the above described set of reactions within the cells is called intermediary metabolism or intermediate metabolism).

新陈代谢（/məˈtæbəlɪzəm/，来自希腊语：μεταβολή metabolē，"变化"）是生物体内维持生命的[[化学反应]]。新陈代谢的三个主要目的是：将食物转化为能量以运行细胞过程；将食物/燃料转化为[[蛋白质]]、[[脂类]]、[[核酸]]和一些[[碳水化合物]]的构件；以及消除[[代谢废物]]。这些酶催化的反应使生物体得以生长和繁殖，维持其结构，并对其环境作出反应。（新陈代谢这个词也可以指生物体内发生的所有化学反应的总和，包括消化和物质在细胞内以及不同细胞之间的运输，在这种情况下，上述细胞内的一系列反应称为中间代谢或中级代谢）。

Metabolic reactions may be categorized as ''[[catabolic]]'' – the ''breaking down'' of compounds (for example, the breaking down of glucose to pyruvate by [[cellular respiration]]); or ''[[anabolic]]'' – the ''building up'' ([[biosynthesis|synthesis]]) of compounds (such as proteins, carbohydrates, lipids, and nucleic acids). Usually, catabolism releases energy, and anabolism consumes energy.

Metabolic reactions may be categorized as catabolic – the breaking down of compounds (for example, the breaking down of glucose to pyruvate by cellular respiration); or anabolic – the building up (synthesis) of compounds (such as proteins, carbohydrates, lipids, and nucleic acids). Usually, catabolism releases energy, and anabolism consumes energy.

新陈代谢反应可分为[[分解代谢]]分解代谢-分解化合物(例如，通过[[细胞呼吸]]将葡萄糖分解为丙酮酸) ; 或合成代谢-合成化合物(例如蛋白质、碳水化合物、脂类和核酸)。通常，分解代谢释放能量，合成代谢消耗能量。

The chemical reactions of metabolism are organized into [[metabolic pathway]]s, in which one chemical is transformed through a series of steps into another chemical, each step being facilitated by a specific [[enzyme]]. Enzymes are crucial to metabolism because they allow organisms to drive desirable reactions that require [[energy]] that will not occur by themselves, by [[Coupling (physics)|coupling]] them to [[spontaneous process|spontaneous reactions]] that release energy. Enzymes act as [[Catalysis|catalysts]] – they allow a reaction to proceed more rapidly – and they also allow the [[Metabolic pathway#Regulation|regulation]] of the rate of a metabolic reaction, for example in response to changes in the [[cell (biology)|cell's]] environment or to [[cell signaling|signals]] from other cells.

The chemical reactions of metabolism are organized into metabolic pathways, in which one chemical is transformed through a series of steps into another chemical, each step being facilitated by a specific enzyme. Enzymes are crucial to metabolism because they allow organisms to drive desirable reactions that require energy that will not occur by themselves, by coupling them to spontaneous reactions that release energy. Enzymes act as catalysts – they allow a reaction to proceed more rapidly – and they also allow the regulation of the rate of a metabolic reaction, for example in response to changes in the cell's environment or to signals from other cells.

新陈代谢的化学反应被组织成代谢途径，在代谢途径中，一种化学物质通过一系列步骤转化为另一种化学物质，每一步都由特定的[[酶]]来推动。酶对新陈代谢至关重要，因为它们通过将生物体与释放能量的自发反应耦合，使生物体能够驱动需要能量的理想反应，而这些反应本身不会发生。酶起催化剂的作用——它们使反应进行得更快——它们还可以调节代谢反应的速率，例如对细胞环境的变化或其他细胞发出的信号作出反应。

The metabolic system of a particular organism determines which substances it will find [[nutrition|nutritious]] and which [[poison]]ous. For example, some [[prokaryote]]s use [[hydrogen sulfide]] as a nutrient, yet this gas is poisonous to animals. The [[basal metabolic rate]] of an organism is the measure of the amount of energy consumed by all of these chemical reactions.

The metabolic system of a particular organism determines which substances it will find nutritious and which poisonous. For example, some prokaryotes use hydrogen sulfide as a nutrient, yet this gas is poisonous to animals. The basal metabolic rate of an organism is the measure of the amount of energy consumed by all of these chemical reactions.

特定生物体的新陈代谢系统决定了哪些物质有营养，哪些有毒。例如，一些[[原核生物]]利用硫化氢作为营养物质，然而这种气体对动物是有毒的<ref name="Physiology1">{{cite book |author=Friedrich C |title=Physiology and genetics of sulfur-oxidizing bacteria |journal=Adv Microb Physiol |volume=39 |issue= |pages=235–89 |year=1998 |pmid=9328649 |doi=10.1016/S0065-2911(08)60018-1 |series=Advances in Microbial Physiology |isbn=978-0-12-027739-1}}</ref>。生物体的[[基础代谢率]]是所有这些化学反应所消耗能量的量度。

A striking feature of metabolism is the similarity of the basic metabolic pathways among vastly different species. For example, the set of [[carboxylic acid]]s that are best known as the intermediates in the [[citric acid cycle]] are present in all known organisms, being found in species as diverse as the [[Unicellular organism|unicellular]] bacterium ''[[Escherichia coli]]'' and huge [[multicellular organism]]s like [[elephant]]s. These similarities in metabolic pathways are likely due to their early appearance in [[evolutionary history of life|evolutionary history]], and their retention because of their [[efficacy]]. The metabolism of cancer cells is also different from the metabolism of normal cells and these differences can be used to find targets for therapeutic intervention in cancer.

A striking feature of metabolism is the similarity of the basic metabolic pathways among vastly different species. For example, the set of carboxylic acids that are best known as the intermediates in the citric acid cycle are present in all known organisms, being found in species as diverse as the unicellular bacterium Escherichia coli and huge multicellular organisms like elephants. These similarities in metabolic pathways are likely due to their early appearance in evolutionary history, and their retention because of their efficacy. The metabolism of cancer cells is also different from the metabolism of normal cells and these differences can be used to find targets for therapeutic intervention in cancer.

新陈代谢的一个显著特征是，不同物种之间的基本新陈代谢途径具有相似性<ref>{{cite journal | vauthors = Pace NR | title = The universal nature of biochemistry | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 98 | issue = 3 | pages = 805–8 | date = January 2001 | pmid = 11158550 | pmc = 33372 | doi = 10.1073/pnas.98.3.805 | bibcode = 2001PNAS...98..805P }}</ref>。例如，作为[[三羧酸循环]]中的中间体，最著名的一组羧酸存在于所有已知的生物体中，它们在单细胞细菌[[大肠杆菌]]和巨大的多细胞生物（如大象）中都能被找到<ref name=SmithE>{{cite journal | vauthors = Smith E, Morowitz HJ | title = Universality in intermediary metabolism | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 101 | issue = 36 | pages = 13168–73 | date = September 2004 | pmid = 15340153 | pmc = 516543 | doi = 10.1073/pnas.0404922101 | bibcode = 2004PNAS..10113168S }}</ref>。这些代谢途径的相似性很可能是由于它们在演化史的早期出现，然后又因为它们的功效而保留下来<ref name=Ebenhoh>{{cite journal | vauthors = Ebenhöh O, Heinrich R | title = Evolutionary optimization of metabolic pathways. Theoretical reconstruction of the stoichiometry of ATP and NADH producing systems | journal = Bulletin of Mathematical Biology | volume = 63 | issue = 1 | pages = 21–55 | date = January 2001 | pmid = 11146883 | doi = 10.1006/bulm.2000.0197 | s2cid = 44260374 }}</ref><ref name=Cascante>{{cite journal | vauthors = Meléndez-Hevia E, Waddell TG, Cascante M | title = The puzzle of the Krebs citric acid cycle: assembling the pieces of chemically feasible reactions, and opportunism in the design of metabolic pathways during evolution | journal = Journal of Molecular Evolution | volume = 43 | issue = 3 | pages = 293–303 | date = September 1996 | pmid = 8703096 | doi = 10.1007/BF02338838 | s2cid = 19107073 | bibcode = 1996JMolE..43..293M }}</ref>。癌细胞的代谢也不同于正常细胞的代谢，这些差异可以用来寻找癌细胞治疗的靶点<ref name="Vander_Heiden_2017">{{cite journal | vauthors = Vander Heiden MG, DeBerardinis RJ | title = Understanding the Intersections between Metabolism and Cancer Biology | journal = Cell | volume = 168 | issue = 4 | pages = 657–669 | date = February 2017 | pmid = 28187287 | pmc = 5329766 | doi = 10.1016/j.cell.2016.12.039 }}</ref>。

== Key biochemicals ==
关键的生物化学成分

{{further|Biomolecule|Cell (biology)|Biochemistry}}

更多信息：生物分子，细胞（生物学）和生物化学

[[File:Trimyristin-3D-vdW.png|right|thumb|upright=1.15|[[三酰甘油脂]]的结构]]

[[File:Human Metabolism - Pathways.jpg|thumb|这张图表描绘了人体新陈代谢的一系列途径。]]

Most of the structures that make up animals, plants and microbes are made from four basic classes of [[molecule]]: [[amino acid]]s, [[carbohydrate]]s , [[nucleic acid]] and [[lipid]]s (often called [[fat]]s). As these molecules are vital for life, metabolic reactions either focus on making these molecules during the construction of cells and tissues, or by breaking them down and using them as a source of energy, by their digestion. These biochemicals can be joined together to make [[polymer]]s such as [[DNA]] and [[protein]]s, essential [[macromolecules]] of life.

Most of the structures that make up animals, plants and microbes are made from four basic classes of molecule: amino acids, carbohydrates , nucleic acid and lipids (often called fats). As these molecules are vital for life, metabolic reactions either focus on making these molecules during the construction of cells and tissues, or by breaking them down and using them as a source of energy, by their digestion. These biochemicals can be joined together to make polymers such as DNA and proteins, essential macromolecules of life.

构成动物、植物和微生物的大部分结构由四种基本分子组成: 氨基酸、糖类化合物、核酸和脂类(通常称为脂肪)。由于这些分子对生命至关重要，新陈代谢反应要么专注于在构建细胞和组织的过程中制造这些分子，要么将这些分子作为能量来源并将其消化分解。这些生化物质可以结合在一起形成DNA和蛋白质之类的聚合物，它们都是生命必不可少的[[大分子聚合物]]<ref>{{cite journal|last=Cooper|first=Geoffrey M.| name-list-style = vanc |date=2000|title=The Molecular Composition of Cells|url=https://www.ncbi.nlm.nih.gov/books/NBK9879/|journal=The Cell: A Molecular Approach. 2nd Edition|language=en}}</ref>。

<center>
{| class=“wikitable” style = “margin-left: auto; margin-right: auto;”
|-
!分子类型 !! [[单体]]形式的名称 !! [[聚合物]]形式的名称 !! 聚合物形态的例子
|-
| 氨基酸 || [[蛋白质]](由多肽组成) || [[纤维蛋白]]和[[球状蛋白]]
|-
| [[碳水化合物]] || [[单糖]] || [[多糖]] || [[淀粉]], [[糖原]] and [[纤维素]]
|-
| [[核酸]] || [[核苷酸]] || [[多核苷酸]] || [[DNA]] and [[RNA]]
|}
</center>

===Amino acids and proteins===
氨基酸和蛋白质

[[Protein]]s are made of [[amino acid]]s arranged in a linear chain joined together by [[peptide bond]]s. Many proteins are [[enzyme]]s that [[catalysis|catalyze]] the chemical reactions in metabolism. Other proteins have structural or mechanical functions, such as those that form the [[cytoskeleton]], a system of [[scaffolding]] that maintains the cell shape.Proteins are also important in [[cell signaling]], [[antibody|immune responses]], [[cell adhesion]], [[active transport]] across membranes, and the [[cell cycle]].Amino acids also contribute to cellular energy metabolism by providing a carbon source for entry into the citric acid cycle ([[tricarboxylic acid cycle]]), especially when a primary source of energy, such as [[glucose]], is scarce, or when cells undergo metabolic stress.

Proteins are made of amino acids arranged in a linear chain joined together by peptide bonds. Many proteins are enzymes that catalyze the chemical reactions in metabolism. Other proteins have structural or mechanical functions, such as those that form the cytoskeleton, a system of scaffolding that maintains the cell shape. Proteins are also important in cell signaling, immune responses, cell adhesion, active transport across membranes, and the cell cycle. Amino acids also contribute to cellular energy metabolism by providing a carbon source for entry into the citric acid cycle (tricarboxylic acid cycle), especially when a primary source of energy, such as glucose, is scarce, or when cells undergo metabolic stress.

蛋白质是由氨基酸组成的线性链，它们通过[[肽键]]连接在一起。许多蛋白质是在新陈代谢中催化化学反应的酶。其他蛋白质具有结构或机械功能，例如那些形成[[细胞骨架]]的蛋白质（细胞骨架是维持细胞形状的支架系统）<ref>{{cite journal | vauthors = Michie KA, Löwe J | title = Dynamic filaments of the bacterial cytoskeleton | journal = Annual Review of Biochemistry | volume = 75 | issue = | pages = 467–92 | year = 2006 | pmid = 16756499 | doi = 10.1146/annurev.biochem.75.103004.142452 | s2cid = 4550126 }}</ref> 。蛋白质在[[细胞信号传导]]、[[免疫反应]]、[[细胞粘附]]、主动跨膜转运和[[细胞周期]]中也很重要<ref name=Nelson>{{cite book | last1 = Nelson | first1 = David L. | first2 = Michael M. | last2 = Cox | name-list-style = vanc | title = Lehninger Principles of Biochemistry | publisher = W. H. Freeman and company | year = 2005 | location = New York | page = [https://archive.org/details/lehningerprincip00lehn_0/page/841 841] | isbn = 978-0-7167-4339-2 | url-access = registration | url = https://archive.org/details/lehningerprincip00lehn_0/page/841 }}</ref> 。氨基酸还通过提供碳源进入细胞三羧酸循环，促进细胞的能量代谢，<ref>{{cite journal | vauthors = Kelleher JK, Bryan BM, Mallet RT, Holleran AL, Murphy AN, Fiskum G | title = Analysis of tricarboxylic acid-cycle metabolism of hepatoma cells by comparison of 14CO2 ratios | journal = The Biochemical Journal | volume = 246 | issue = 3 | pages = 633–9 | date = September 1987 | pmid = 3120698 | pmc = 1148327 | doi = 10.1042/bj2460633 }}</ref>尤其是在[[葡萄糖]]等主要能量来源匮乏或细胞发生代谢应激时<ref>{{cite journal | vauthors = Hothersall JS, Ahmed A | title = Metabolic fate of the increased yeast amino Acid uptake subsequent to catabolite derepression | journal = Journal of Amino Acids | volume = 2013 | pages = 461901 | year = 2013 | pmid = 23431419 | pmc = 3575661 | doi = 10.1155/2013/461901 }}</ref>。

===Lipids===
脂类
[[Lipid]]s are the most diverse group of biochemicals. Their main structural uses are as part of [[biological membrane]]s both internal and external, such as the [[cell membrane]], or as a source of energy. Lipids are usually defined as [[hydrophobe|hydrophobic]] or [[amphiphiles|amphipathic]] biological molecules but will dissolve in [[organic solvent]]s such as [[ethanol|alcohol]], [[benzene]] or [[chloroform]]. The [[fat]]s are a large group of compounds that contain [[fatty acid]]s and [[glycerol]]; a glycerol molecule attached to three fatty acid [[ester]]s is called a [[triglyceride|triacylglyceride]]. Several variations on this basic structure exist, including backbones such as [[sphingosine]] in the [[sphingomyelin]], and [[hydrophile|hydrophilic]] groups such as [[phosphate]] as in [[phospholipid]]s. [[Steroid]]s such as [[sterol]] are another major class of lipids.

Lipids are the most diverse group of biochemicals. Their main structural uses are as part of biological membranes both internal and external, such as the cell membrane, or as a source of energy. Lipids are usually defined as hydrophobic or amphipathic biological molecules but will dissolve in organic solvents such as alcohol, benzene or chloroform. The fats are a large group of compounds that contain fatty acids and glycerol; a glycerol molecule attached to three fatty acid esters is called a triacylglyceride. Several variations on this basic structure exist, including backbones such as sphingosine in the sphingomyelin, and hydrophilic groups such as phosphate as in phospholipids. Steroids such as sterol are another major class of lipids.

脂类是最多样化的生物化学物质。它们的主要结构用途是作为[[生物膜]]内部和外部的一部分，如[[细胞膜]]，或作为能量来源<ref name=Nelson/>。脂类通常被定义为疏水性或两亲性的生物分子，但会溶解在有机溶剂中，如酒精、苯或氯仿。<ref>{{cite journal | vauthors = Fahy E, Subramaniam S, Brown HA, Glass CK, Merrill AH, Murphy RC, Raetz CR, Russell DW, Seyama Y, Shaw W, Shimizu T, Spener F, van Meer G, VanNieuwenhze MS, White SH, Witztum JL, Dennis EA | display-authors = 6 | title = A comprehensive classification system for lipids | journal = Journal of Lipid Research | volume = 46 | issue = 5 | pages = 839–61 | date = May 2005 | pmid = 15722563 | doi = 10.1194/jlr.E400004-JLR200 | doi-access = free }}</ref>脂肪是一大类含有脂肪酸和甘油的化合物，一个甘油分子连接到三个脂肪酸酯即称为三酰甘油酯。<ref>{{cite web|title=Lipid nomenclature Lip-1 & Lip-2|url=https://www.qmul.ac.uk/sbcs/iupac/lipid/lip1n2.html#p11|access-date=2020-06-06|website=www.qmul.ac.uk}}</ref>这种基本结构存在一些变异，包括主骨(如鞘磷脂中到鞘氨醇)和亲水基(如磷脂中的磷酸盐)。[[类固醇]]，如[[固醇]]，是另一类主要的脂类<ref>{{cite book|edition=8|title=Biochemistry|location=New York|isbn=978-1-4641-2610-9|oclc=913469736 | vauthors = Berg JM, Tymoczko JL, Gatto Jr GJ, Stryer L |date=8 April 2015|publisher=W. H. Freeman|pages=362}}</ref>。

===Carbohydrates===
碳水化合物

[[File:Glucose Fisher to Haworth.gif|thumb|upright=1.15|right|alt=The straight chain form consists of four C H O H groups linked in a row, capped at the ends by an aldehyde group C O H and a methanol group C H 2 O H. To form the ring, the aldehyde group combines with the O H group of the next-to-last carbon at the other end, just before the methanol group.|[[Glucose]] can exist in both a straight-chain and ring form.]]

[[Glucose can exist in both a straight-chain and ring form.]]

[葡萄糖可以以直链和环的形式存在。]

[[Carbohydrate]]s are [[aldehyde]]s or [[ketone]]s, with many [[hydroxyl]] groups attached, that can exist as straight chains or rings. Carbohydrates are the most abundant biological molecules, and fill numerous roles, such as the storage and transport of [[energy]] ([[starch]], [[glycogen]]) and structural components ([[cellulose]] in plants, [[chitin]] in animals). The basic carbohydrate units are called [[monosaccharide]]s and include [[galactose]], [[fructose]], and most importantly [[glucose]]. Monosaccharides can be linked together to form [[polysaccharide]]s in almost limitless ways.

Carbohydrates are aldehydes or ketones, with many hydroxyl groups attached, that can exist as straight chains or rings. Carbohydrates are the most abundant biological molecules, and fill numerous roles, such as the storage and transport of energy (starch, glycogen) and structural components (cellulose in plants, chitin in animals). The basic carbohydrate units are called monosaccharides and include galactose, fructose, and most importantly glucose. Monosaccharides can be linked together to form polysaccharides in almost limitless ways.

碳水化合物是醛或酮，带有许多羟基，能以直链或环的形式存在。碳水化合物是最丰富的生物分子，承担着许多作用，如能量的储存和运输（淀粉、糖原）和作为结构要件（植物的纤维素、动物的甲壳素）。基本的碳水化合物单位称为单糖<ref name=Nelson/>，包括半乳糖、果糖以及最重要的葡萄糖。单糖能以几乎无限多样的方式连接在一起形成多糖<ref>{{cite journal | vauthors = Raman R, Raguram S, Venkataraman G, Paulson JC, Sasisekharan R | title = Glycomics: an integrated systems approach to structure-function relationships of glycans | journal = Nature Methods | volume = 2 | issue = 11 | pages = 817–24 | date = November 2005 | pmid = 16278650 | doi = 10.1038/nmeth807 | s2cid = 4644919 }}</ref>。

===Nucleotides===

核苷酸
The two nucleic acids, DNA and [[RNA]], are polymers of [[nucleotide]]s. Each nucleotide is composed of a phosphate attached to a [[ribose]] or [[deoxyribose]] sugar group which is attached to a [[nitrogenous base]]. Nucleic acids are critical for the storage and use of genetic information, and its interpretation through the processes of [[transcription (genetics)|transcription]] and [[protein biosynthesis]]. This information is protected by [[DNA repair]] mechanisms and propagated through [[DNA replication]]. Many [[virus]]es have an [[RNA virus|RNA genome]], such as [[HIV]], which uses [[reverse transcription]] to create a DNA template from its viral RNA genome. RNA in [[ribozyme]]s such as [[spliceosome]]s and [[ribosome]]s is similar to enzymes as it can catalyze chemical reactions. Individual [[nucleoside]]s are made by attaching a [[nucleobase]] to a [[ribose]] sugar. These bases are [[heterocyclic]] rings cono ptaining nitrogen, classified as [[purine]]s or [[pyrimidine]]s. Nucleotides also act as coenzymes in metabolic-group-transfer reactions.

The two nucleic acids, DNA and RNA, are polymers of nucleotides. Each nucleotide is composed of a phosphate attached to a ribose or deoxyribose sugar group which is attached to a nitrogenous base. Nucleic acids are critical for the storage and use of genetic information, and its interpretation through the processes of transcription and protein biosynthesis.This information is protected by DNA repair mechanisms and propagated through DNA replication. Many viruses have an RNA genome, such as HIV, which uses reverse transcription to create a DNA template from its viral RNA genome.RNA in ribozymes such as spliceosomes and ribosomes is similar to enzymes as it can catalyze chemical reactions. Individual nucleosides are made by attaching a nucleobase to a ribose sugar. These bases are heterocyclic rings containing nitrogen, classified as purines or pyrimidines. Nucleotides also act as coenzymes in metabolic-group-transfer reactions.

DNA和RNA这两种核酸是核苷酸的聚合物。每个核苷酸都是由一个磷酸连接到核糖或脱氧核糖糖基上形成的，而核糖或脱氧核糖糖基又连接到含氮碱基上。核酸对于遗传信息的储存和使用，以及通过转录和蛋白质生物合成过程对其进行解释至关重要。这些信息受到DNA修复机制的保护<ref name=Nelson/>，并通过DNA复制进行传播。许多病毒都有RNA基因组，如HIV病毒，它利用[[逆转录]]从其病毒RNA基因组中创建DNA模板。核糖体和核糖体等核糖体中的RNA类似于酶<ref>{{cite journal | vauthors = Sierra S, Kupfer B, Kaiser R | title = Basics of the virology of HIV-1 and its replication | journal = Journal of Clinical Virology | volume = 34 | issue = 4 | pages = 233–44 | date = December 2005 | pmid = 16198625 | doi = 10.1016/j.jcv.2005.09.004 }}</ref>，因为它可以催化化学反应。单个核苷是通过将核碱基连接到核糖上制成的。这些碱基是含氮的杂环，分为嘌呤或嘧啶。核苷酸还在代谢基团转移反应中充当辅酶<ref name=Wimmer>{{cite journal | vauthors = Wimmer MJ, Rose IA | title = Mechanisms of enzyme-catalyzed group transfer reactions | journal = Annual Review of Biochemistry | volume = 47 | issue = | pages = 1031–78 | year = 1978 | pmid = 354490 | doi = 10.1146/annurev.bi.47.070178.005123 }}</ref>。

===Coenzymes===
辅酶

[[File:Acetyl-CoA-2D.svg|thumb|right|upright=1.35|[[乙酰辅酶A]]结构。可转移的[[乙酰基]]与最左边的硫原子成键结合。]]

{{main|Coenzyme}}

Metabolism involves a vast array of chemical reactions, but most fall under a few basic types of reactions that involve the transfer of [[functional group]]s of atoms and their bonds within molecules. This common chemistry allows cells to use a small set of metabolic intermediates to carry chemical groups between different reactions. These group-transfer intermediates are called [[coenzyme]]s. Each class of group-transfer reactions is carried out by a particular coenzyme, which is the [[substrate (biochemistry)|substrate]] for a set of enzymes that produce it, and a set of enzymes that consume it. These coenzymes are therefore continuously made, consumed and then recycled.

Metabolism involves a vast array of chemical reactions, but most fall under a few basic types of reactions that involve the transfer of functional groups of atoms and their bonds within molecules. This common chemistry allows cells to use a small set of metabolic intermediates to carry chemical groups between different reactions. These group-transfer intermediates are called coenzymes. Each class of group-transfer reactions is carried out by a particular coenzyme, which is the substrate for a set of enzymes that produce it, and a set of enzymes that consume it. These coenzymes are therefore continuously made, consumed and then recycled.

新陈代谢涉及大量的化学反应，但大多数属于几种基本类型的反应，涉及原子的官能团及其键在分子内的转移。这种常见的化学反应使细胞能够用一小套代谢中间体在不同反应之间携带化学基团<ref>{{cite journal | vauthors = Mitchell P | title = The Ninth Sir Hans Krebs Lecture. Compartmentation and communication in living systems. Ligand conduction: a general catalytic principle in chemical, osmotic and chemiosmotic reaction systems | journal = European Journal of Biochemistry | volume = 95 | issue = 1 | pages = 1–20 | date = March 1979 | pmid = 378655 | doi = 10.1111/j.1432-1033.1979.tb12934.x }}</ref>。这些基团转移中间体称为辅酶<ref name=Wimmer/>。每一类基团转移反应都是由一种特定的辅酶进行的，它是一组产生它的酶和消耗它的酶的底物。因此，这些辅酶不断地被制造、消耗，然后循环利用<ref name=Dimroth>{{cite journal | vauthors = Dimroth P, von Ballmoos C, Meier T | title = Catalytic and mechanical cycles in F-ATP synthases. Fourth in the Cycles Review Series | journal = EMBO Reports | volume = 7 | issue = 3 | pages = 276–82 | date = March 2006 | pmid = 16607397 | pmc = 1456893 | doi = 10.1038/sj.embor.7400646 }}</ref>。

One central coenzyme is [[adenosine triphosphate]] (ATP), the universal energy currency of cells. This nucleotide is used to transfer chemical energy between different chemical reactions. There is only a small amount of ATP in cells, but as it is continuously regenerated, the human body can use about its own weight in ATP per day. ATP acts as a bridge between [[catabolism]] and [[anabolism]]. Catabolism breaks down molecules, and anabolism puts them together. Catabolic reactions generate ATP, and anabolic reactions consume it. It also serves as a carrier of phosphate groups in [[phosphorylation]] reactions.

One central coenzyme is adenosine triphosphate (ATP), the universal energy currency of cells. This nucleotide is used to transfer chemical energy between different chemical reactions. There is only a small amount of ATP in cells, but as it is continuously regenerated, the human body can use about its own weight in ATP per day. ATP acts as a bridge between catabolism and anabolism. Catabolism breaks down molecules, and anabolism puts them together. Catabolic reactions generate ATP, and anabolic reactions consume it. It also serves as a carrier of phosphate groups in phosphorylation reactions.

其中一种中心辅酶是三磷酸腺苷（ATP），它是细胞的通用能源货币。这种核苷酸在不同的化学反应之间传递化学能。细胞中只有少量的ATP，但由于ATP是不断再生的，所以人体每天可以使用大约相当于自身重量的ATP<ref name=Dimroth/>。ATP是分解代谢和合成代谢之间的桥梁。分解代谢分解分子，合成代谢则将它们组合在一起。分解反应产生ATP，合成代谢反应则消耗ATP。它也是磷酸化反应中磷酸基团的载体<ref>{{cite journal | vauthors = Bonora M, Patergnani S, Rimessi A, De Marchi E, Suski JM, Bononi A, Giorgi C, Marchi S, Missiroli S, Poletti F, Wieckowski MR, Pinton P | display-authors = 6 | title = ATP synthesis and storage | journal = Purinergic Signalling | volume = 8 | issue = 3 | pages = 343–57 | date = September 2012 | pmid = 22528680 | pmc = 3360099 | doi = 10.1007/s11302-012-9305-8 }}</ref>。

A [[vitamin]] is an organic compound needed in small quantities that cannot be made in cells. In [[human nutrition]], most vitamins function as coenzymes after modification; for example, all water-soluble vitamins are phosphorylated or are coupled to nucleotides when they are used in cells. [[Nicotinamide adenine dinucleotide]] (NAD+), a derivative of vitamin B3 ([[niacin]]), is an important coenzyme that acts as a hydrogen acceptor. Hundreds of separate types of [[dehydrogenase]]s remove electrons from their substrates and [[redox|reduce]] NAD+ into NADH. This reduced form of the coenzyme is then a substrate for any of the [[reductase]]s in the cell that need to reduce their substrates. Nicotinamide adenine dinucleotide exists in two related forms in the cell, NADH and NADPH. The NAD+/NADH form is more important in catabolic reactions, while NADP+/NADPH is used in anabolic reactions.

A vitamin is an organic compound needed in small quantities that cannot be made in cells. In human nutrition, most vitamins function as coenzymes after modification; for example, all water-soluble vitamins are phosphorylated or are coupled to nucleotides when they are used in cells. Nicotinamide adenine dinucleotide (NAD+), a derivative of vitamin B3 (niacin), is an important coenzyme that acts as a hydrogen acceptor. Hundreds of separate types of dehydrogenases remove electrons from their substrates and reduce NAD+ into NADH. This reduced form of the coenzyme is then a substrate for any of the reductases in the cell that need to reduce their substrates. Nicotinamide adenine dinucleotide exists in two related forms in the cell, NADH and NADPH. The NAD+/NADH form is more important in catabolic reactions, while NADP+/NADPH is used in anabolic reactions.

[[维生素]]是一类细胞不能合成的微量有机化合物。在人体营养中，大多数维生素经过修饰后都具有辅酶的功能，例如，所有水溶性维生素在细胞中使用时都会被磷酸化或与核苷酸偶联<ref>{{cite journal|last1=Berg|first1=Jeremy M.|last2=Tymoczko|first2=John L.|last3=Stryer|first3=Lubert | name-list-style = vanc |date=2002|title=Vitamins Are Often Precursors to Coenzymes|url=https://www.ncbi.nlm.nih.gov/books/NBK22549/|journal=Biochemistry. 5th Edition|language=en}}</ref>。[[烟酰胺腺嘌呤二核苷酸]](NAD+)是维生素B3(烟酸)的衍生物，它是一种重要的辅酶，起着氢接受器的作用。数百种不同类型的脱氢酶从其底物中去除电子，并将NAD+还原成NADH。这种还原形式的辅酶是细胞中任何需要还原其底物的还原酶的底物。烟酰胺腺嘌呤二核苷酸在细胞中以两种相关形式存在<ref>{{cite journal | vauthors = Pollak N, Dölle C, Ziegler M | title = The power to reduce: pyridine nucleotides--small molecules with a multitude of functions | journal = The Biochemical Journal | volume = 402 | issue = 2 | pages = 205–18 | date = March 2007 | pmid = 17295611 | pmc = 1798440 | doi = 10.1042/BJ20061638 }}</ref>，即NADH和NADPH。NAD +/NADH 形式在分解代谢反应中起重要作用，而 NADP +/NADPH 形式在分解代谢反应中起重要作用<ref>{{cite book|last=Fatih|first=Yildiz | name-list-style = vanc |title=Advances in food biochemistry|publisher=CRC Press|year=2009|isbn=978-1-4200-0769-5|location=Boca Raton|pages=228|oclc=607553259}}</ref>。

[[File:1GZX Haemoglobin.png|thumb|upright=1.35|right|The structure of iron-containing [[hemoglobin]]. 含铁[[血红蛋白]]的结构。蛋白质亚基为红色和蓝色，含铁血红素基为绿色。]]

===Mineral and cofactors===
矿物质和辅因子

{{further||Bioinorganic chemistry}}

Inorganic elements play critical roles in metabolism; some are abundant (e.g. [[sodium]] and [[potassium]]) while others function at minute concentrations. About 99% of a human's body weight is made up of the elements [[carbon]], [[nitrogen]], [[calcium]], [[sodium]], [[chlorine]], [[potassium]], [[hydrogen]], [[phosphorus]], [[oxygen]] and [[sulfur]]. [[Organic compound]]s (proteins, lipids and carbohydrates) contain the majority of the carbon and nitrogen; most of the oxygen and hydrogen is present as water.

Inorganic elements play critical roles in metabolism; some are abundant (e.g. sodium and potassium) while others function at minute concentrations. About 99% of a human's body weight is made up of the elements carbon, nitrogen, calcium, sodium, chlorine, potassium, hydrogen, phosphorus, oxygen and sulfur. Organic compounds (proteins, lipids and carbohydrates) contain the majority of the carbon and nitrogen; most of the oxygen and hydrogen is present as water<ref name="Heymsfield">{{cite journal | vauthors = Heymsfield SB, Waki M, Kehayias J, Lichtman S, Dilmanian FA, Kamen Y, Wang J, Pierson RN | display-authors = 6 | title = Chemical and elemental analysis of humans in vivo using improved body composition models | journal = The American Journal of Physiology | volume = 261 | issue = 2 Pt 1 | pages = E190-8 | date = August 1991 | pmid = 1872381 | doi = 10.1152/ajpendo.1991.261.2.E190 }}</ref>.

无机元素在新陈代谢中起着关键作用; 有些元素含量丰富(例如:钠和钾) ，而另一些元素则在微量浓度下发挥作用。人的体重约99%是由碳、氮、钙、钠、氯、钾、氢、磷、氧和硫等元素组成。有机化合物（蛋白质、脂类和碳水化合物）含有大部分的碳和氮；大部分的氧和氢以水的形式存在。

The abundant inorganic elements act as [[electrolyte]]s. The most important ions are [[sodium]], [[potassium]], [[calcium]], [[magnesium]], [[chloride]], [[phosphate]] and the organic ion [[bicarbonate]]. The maintenance of precise [[ion gradient]]s across [[cell membrane]]s maintains [[osmotic pressure]] and [[pH]]. Ions are also critical for [[nerve]] and [[muscle]] function, as [[action potential]]s in these tissues are produced by the exchange of electrolytes between the [[extracellular fluid]] and the cell's fluid, the [[cytosol]]. Electrolytes enter and leave cells through proteins in the cell membrane called [[ion channel]]s. For example, [[muscle contraction]] depends upon the movement of calcium, sodium and potassium through ion channels in the cell membrane and [[T-tubule]]s.

The abundant inorganic elements act as electrolytes. The most important ions are sodium, potassium, calcium, magnesium, chloride, phosphate and the organic ion bicarbonate. The maintenance of precise ion gradients across cell membranes maintains osmotic pressure and pH. Ions are also critical for nerve and muscle function, as action potentials in these tissues are produced by the exchange of electrolytes between the extracellular fluid and the cell's fluid, the cytosol. Electrolytes enter and leave cells through proteins in the cell membrane called ion channels. For example, muscle contraction depends upon the movement of calcium, sodium and potassium through ion channels in the cell membrane and T-tubules.

丰富的无机元用作电解质。最重要的离子是钠、钾、钙、镁、氯化物、磷酸盐和有机离子重碳酸盐。维持细胞膜上精确的离子梯度可以维持[[渗透压]]和 ph 值。离子对于神经和肌肉功能也是至关重要的<ref>{{cite book |date=| chapter = Electrolyte Balance | chapter-url=https://opentextbc.ca/anatomyandphysiology/chapter/26-3-electrolyte-balance/ | title = Anatomy and Physiology | publisher = OpenStax |access-date=23 June 2020 }}</ref>，因为这些组织中的动作电位是由细胞外液和细胞液之间的电解质交换产生的。电解质通过细胞膜上称为离子通道的蛋白质进入和离开细胞<ref>{{cite book |last1=Lodish |first1=Harvey |last2=Berk |first2=Arnold |last3=Zipursky |first3=S. Lawrence |last4=Matsudaira |first4=Paul |last5=Baltimore |first5=David |last6=Darnell |first6=James | name-list-style = vanc |date=2000| chapter =The Action Potential and Conduction of Electric Impulses|chapter-url= https://www.ncbi.nlm.nih.gov/books/NBK21668/ |title =Molecular Cell Biology | edition = 4th |language=en|via=NCBI}}</ref> 。例如，肌肉收缩依赖于钙、钠和钾通过细胞膜和T管道中的离子通道的运动<ref>{{cite journal | vauthors = Dulhunty AF | title = Excitation-contraction coupling from the 1950s into the new millennium | journal = Clinical and Experimental Pharmacology & Physiology | volume = 33 | issue = 9 | pages = 763–72 | date = September 2006 | pmid = 16922804 | doi = 10.1111/j.1440-1681.2006.04441.x | s2cid = 37462321 }}</ref>。

[[Transition metal]]s are usually present as [[trace element]]s in organisms, with [[zinc]] and [[iron]] being most abundant of those. These metals are used in some proteins as [[Cofactor (biochemistry)|cofactors]] and are essential for the activity of enzymes such as [[catalase]] and oxygen-carrier proteins such as [[hemoglobin]]. Metal cofactors are bound tightly to specific sites in proteins; although enzyme cofactors can be modified during catalysis, they always return to their original state by the end of the reaction catalyzed. Metal micronutrients are taken up into organisms by specific transporters and bind to storage proteins such as [[ferritin]] or [[metallothionein]] when not in use.

Transition metals are usually present as trace elements in organisms, with zinc and iron being most abundant of those. These metals are used in some proteins as cofactors and are essential for the activity of enzymes such as catalase and oxygen-carrier proteins such as hemoglobin. Metal cofactors are bound tightly to specific sites in proteins; although enzyme cofactors can be modified during catalysis, they always return to their original state by the end of the reaction catalyzed. Metal micronutrients are taken up into organisms by specific transporters and bind to storage proteins such as ferritin or metallothionein when not in use.

过渡金属通常以微量元素的形式存在于生物体内，其中锌和铁最为丰富<ref>{{cite book| vauthors = Torres-Romero JC, Alvarez-Sánchez ME, Fernández-Martín K, Alvarez-Sánchez LC, Arana-Argáez V, Ramírez-Camacho M, Lara-Riegos J | chapter=Zinc Efflux in Trichomonas vaginalis: In Silico Identification and Expression Analysis of CDF-Like Genes|date=2018| title =Quantitative Models for Microscopic to Macroscopic Biological Macromolecules and Tissues|pages=149–168| veditors = Olivares-Quiroz L, Resendis-Antonio O |place=Cham|publisher=Springer International Publishing|language=en|doi=10.1007/978-3-319-73975-5_8|isbn=978-3-319-73975-5 }}</ref>。这些金属元素在某些蛋白质中作为辅因子，是催化酶等酶和血红蛋白等氧载体蛋白活性所必需的金属辅因子。<ref>{{cite book|last=Craig Will|first=Leonard Ashley | name-list-style = vanc |title=Manufacturing Engineering & Technology|publisher=Scientific e-Resources|year=2019|isbn=9781839472428|location=Waltham Abbey|pages=190–196}}</ref>金属辅因子与蛋白质中的特定位点紧密结合，虽然在催化过程中酶的辅因子可以被改变，但在催化反应结束时，它们总是恢复到原来的状态。金属微量营养素由特定的转运体带入生物体内，不用时与储存蛋白如铁蛋白或金属硫蛋白结合<ref>{{cite journal | vauthors = Cousins RJ, Liuzzi JP, Lichten LA | title = Mammalian zinc transport, trafficking, and signals | journal = The Journal of Biological Chemistry | volume = 281 | issue = 34 | pages = 24085–9 | date = August 2006 | pmid = 16793761 | doi = 10.1074/jbc.R600011200 | url = https://www.jbc.org/content/281/34/24085 | doi-access = free }}</ref><ref>{{cite journal | vauthors = Dunn LL, Suryo Rahmanto Y, Richardson DR | title = Iron uptake and metabolism in the new millennium | journal = Trends in Cell Biology | volume = 17 | issue = 2 | pages = 93–100 | date = February 2007 | pmid = 17194590 | doi = 10.1016/j.tcb.2006.12.003 }}</ref>。

==Catabolism==
分解代谢

[[Catabolism]] is the set of metabolic processes that break down large molecules. These include breaking down and oxidizing food molecules. The purpose of the catabolic reactions is to provide the energy and components needed by anabolic reactions which build molecules. The exact nature of these catabolic reactions differ from organism to organism, and organisms can be classified based on their sources of energy and carbon (their [[primary nutritional groups]]), as shown in the table below. Organic molecules are used as a source of energy by [[organotroph]]s, while [[lithotroph]]s use inorganic substrates, and [[phototroph]]s capture sunlight as [[Potential energy#Chemical potential energy|chemical energy]].However, all these different forms of metabolism depend on [[redox]] reactions that involve the transfer of electrons from reduced donor molecules such as [[organic molecule]]s, water, [[ammonia]], [[hydrogen sulfide]] or [[Ferrous|ferrous ions]] to acceptor molecules such as [[oxygen]], [[nitrate]] or [[sulfate]]. In animals, these reactions involve complex [[organic molecule]]s that are broken down to simpler molecules, such as [[carbon dioxide]] and water. In [[photosynthesis|photosynthetic]] organisms, such as plants and [[cyanobacteria]], these electron-transfer reactions do not release energy but are used as a way of storing energy absorbed from sunlight.

Catabolism is the set of metabolic processes that break down large molecules. These include breaking down and oxidizing food molecules. The purpose of the catabolic reactions is to provide the energy and components needed by anabolic reactions which build molecules. The exact nature of these catabolic reactions differ from organism to organism, and organisms can be classified based on their sources of energy and carbon (their primary nutritional groups), as shown in the table below. Organic molecules are used as a source of energy by organotrophs, while lithotrophs use inorganic substrates, and phototrophs capture sunlight as chemical energy. However, all these different forms of metabolism depend on redox reactions that involve the transfer of electrons from reduced donor molecules such as organic molecules, water, ammonia, hydrogen sulfide or ferrous ions to acceptor molecules such as oxygen, nitrate or sulfate. In animals, these reactions involve complex organic molecules that are broken down to simpler molecules, such as carbon dioxide and water. In photosynthetic organisms, such as plants and cyanobacteria, these electron-transfer reactions do not release energy but are used as a way of storing energy absorbed from sunlight.

分解代谢是指分解大分子的一系列代谢过程。其中包括分解和氧化食物分子。分解代谢反应的目的是为构建分子的合成代谢反应提供所需的能量和成分。这些分解代谢反应的确切性质因生物体而异<ref name="Alberts 2002">{{cite book |last1=Alberts|first1=Bruce|last2=Johnson|first2=Alexander|last3=Lewis|first3=Julian|last4=Raff|first4=Martin|last5=Roberts|first5=Keith|last6=Walter|first6=Peter| name-list-style = vanc |date=2002|chapter =How Cells Obtain Energy from Food|url=https://www.ncbi.nlm.nih.gov/books/NBK26882/|title =Molecular Biology of the Cell | edition = 4th |language=en|via=NCBI}}</ref>，生物体可以根据它们的能量和碳的来源（其主要营养组）进行分类，如下表所示。有机养生物把有机分子作为能量来源，而岩养生物利用无机基质，光养生物利用阳光（获得化学能）<ref>{{cite journal|last=Raven|first=Ja| name-list-style = vanc |date=2009-09-03|title=Contributions of anoxygenic and oxygenic phototrophy and chemolithotrophy to carbon and oxygen fluxes in aquatic environments|url=http://www.int-res.com/abstracts/ame/v56/n2-3/p177-192/|journal=Aquatic Microbial Ecology|language=en|volume=56|pages=177–192|doi=10.3354/ame01315|issn=0948-3055|doi-access=free}}</ref> 。然而，所有这些不同形式的新陈代谢都依赖于氧化还原反应，这些反应涉及电子从还原的供体分子（如有机分子，水，氨，硫化氢或亚铁离子）转移到受体分子（如氧，硝酸盐或硫酸盐）。在动物中，这些反应涉及复杂的有机分子，它们被分解成更简单的分子，如二氧化碳和水。在诸如植物和蓝藻这样的光合生物体中，这些电子转移反应不释放能量，而是用来储存从阳光中吸收的能量<ref name=Nelson2004>{{cite journal | vauthors = Nelson N, Ben-Shem A | title = The complex architecture of oxygenic photosynthesis | journal = Nature Reviews. Molecular Cell Biology | volume = 5 | issue = 12 | pages = 971–82 | date = December 2004 | pmid = 15573135 | doi = 10.1038/nrm1525 | s2cid = 5686066 }}</ref>。

{| class="wikitable float-right" style="text-align:center; width:50%;"

{| class="wikitable float-right" style="text-align:center; width:50%;"

{ | class = “ wikitable float-right” style = “ text-align: center; width: 50% ; ”

|+Classification of organisms based on their metabolism <ref>{{cite book| vauthors = Madigan MT, Martinko JM |title=Brock Mikrobiologie|date=2006|publisher=Pearson Studium|isbn=3-8273-7187-2|edition=11., überarb. Aufl|location=München|pages=604, 621|oclc=162303067}}</ref>

|+Classification of organisms based on their metabolism

| + 根据其新陈代谢对生物进行分类

|-

|-

|-

| rowspan="2" style="background:#ff0;"|Energy source || style="background:#ff0;"| sunlight || style="background:#ff0;"| photo- || rowspan=2 colspan=2 |   || rowspan="6" style="background:#7fc31c;"| -troph

| rowspan="2" style="background:#ff0;"|Energy source || style="background:#ff0;"| sunlight || style="background:#ff0;"| photo- || rowspan=2 colspan=2 |   || rowspan="6" style="background:#7fc31c;"| -troph

能量源
|- style="background:#ff0;"

|- style="background:#ff0;"

|| Preformed molecules || style="background:#ff0;"| chemo-

|| Preformed molecules || style="background:#ff0;"| chemo-

预制分子 | | | | style = ”背景: # ff0; ” | 化疗-

|-

|-

| rowspan="2" style="background:#ffb300;"| Electron donor || style="background:#ffb300;"| [[organic compound]] || rowspan=2 |   || style="background:#ffb300;"| organo- || rowspan=2 |  

| rowspan="2" style="background:#ffb300;"| Electron donor || style="background:#ffb300;"| organic compound || rowspan=2 |   || style="background:#ffb300;"| organo- || rowspan=2 |  

有机化合物 | rowspan = 2 | | | style = ”背景: # ffb300; ” | organic compound = 2 | | | style = ”背景: # ffb300; ” | organo-| rowspan = 2 |

|- style="background:#ffb300;"

|- style="background:#ffb300;"

|-style = ”背景: # ffb300; ”

|| [[inorganic compound]] || style="background:#ffb300;"| litho-

|| inorganic compound || style="background:#ffb300;"| litho-

无机化合物: # ffb300

|-

|-

|-

| rowspan="2" style="background:#fb805f;"| Carbon source || style="background:#fb805f;"| [[organic compound]] || rowspan=2 colspan=2 |   || style="background:#fb805f;"| hetero-

| rowspan="2" style="background:#fb805f;"| Carbon source || style="background:#fb805f;"| organic compound || rowspan=2 colspan=2 |   || style="background:#fb805f;"| hetero-

2 | | rowspan = 2 | | | style = “ background: # fb805f; ” | Carbon source | style = “ background: # fb805f; ” | organic compound | rowspan = 2 colspan = 2 | | | | style = “ background: # fb805f; ” | hetero-
碳源
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|-style = “ background: # fb805f; ”

|| [[inorganic compound]] || style="background:#fb805f;"| auto-

|| inorganic compound || style="background:#fb805f;"| auto-

无机化合物: fb805f

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The most common set of catabolic reactions in animals can be separated into three main stages. In the first stage, large organic molecules, such as [[protein]]s, [[polysaccharide]]s or [[lipid]]s, are digested into their smaller components outside cells. Next, these smaller molecules are taken up by cells and converted to smaller molecules, usually [[acetyl-CoA|acetyl coenzyme A]] (acetyl-CoA), which releases some energy. Finally, the acetyl group on the CoA is oxidised to water and carbon dioxide in the [[citric acid cycle]] and [[electron transport chain]], releasing the energy that is stored by reducing the coenzyme [[nicotinamide adenine dinucleotide]] (NAD+) into NADH.

The most common set of catabolic reactions in animals can be separated into three main stages. In the first stage, large organic molecules, such as proteins, polysaccharides or lipids, are digested into their smaller components outside cells. Next, these smaller molecules are taken up by cells and converted to smaller molecules, usually acetyl coenzyme A (acetyl-CoA), which releases some energy. Finally, the acetyl group on the CoA is oxidised to water and carbon dioxide in the citric acid cycle and electron transport chain, releasing the energy that is stored by reducing the coenzyme nicotinamide adenine dinucleotide (NAD+) into NADH.

动物中最常见的分解代谢反应可以分为三个主要阶段。在第一阶段，大的有机分子，如蛋白质，多糖或脂类，在细胞外被消化成较小的分子。接下来，这些较小的分子被细胞吸收并转化成更小的分子，通常是乙酰辅酶A (acetyl-CoA) ，并释放出一些能量。最后，辅酶 A 上的乙酰基在三羧酸循环和电子传递链中被氧化成水和二氧化碳，释放出储存的能量，将辅酶烟酰胺腺嘌呤二核苷酸（NAD+）还原成NADH<ref name="Alberts 2002"/>。

===Digestion===
消化

{{further|Digestion|Gastrointestinal tract}}

更多信息：消化和胃肠道

Macromolecules cannot be directly processed by cells. Macromolecules must be broken into smaller units before they can be used in cell metabolism. Different classes of enzymes were being used to digest these polymers. These [[digestive enzyme]]s include [[protease]]s that digest proteins into amino acids, as well as [[glycoside hydrolase]]s that digest polysaccharides into simple sugars known as [[monosaccharides]].

Macromolecules cannot be directly processed by cells. Macromolecules must be broken into smaller units before they can be used in cell metabolism. Different classes of enzymes were being used to digest these polymers. These digestive enzymes include proteases that digest proteins into amino acids, as well as glycoside hydrolases that digest polysaccharides into simple sugars known as monosaccharides.

大分子不能直接被细胞处理。大分子必须先被分解成较小的单位，才能用于细胞代谢。不同类别的酶被用来消化这些聚合物。这些消化酶包括将蛋白质消化成氨基酸的蛋白酶，以及将多糖消化成单糖的糖苷水解酶<ref>{{cite book|last=Demirel, Yaşar|title=Energy : production, conversion, storage, conservation, and coupling|publisher=Springer|year=2016|isbn=978-3-319-29650-0|edition=Second|location=Lincoln|pages=431|oclc=945435943}}</ref>。

Microbes simply secrete digestive enzymes into their surroundings, while animals only secrete these enzymes from specialized cells in their [[Gastrointestinal tract|guts]], including the [[stomach]] and [[pancreas]], and [[salivary gland]]s. The amino acids or sugars released by these extracellular enzymes are then pumped into cells by [[active transport]] proteins.

Microbes simply secrete digestive enzymes into their surroundings, while animals only secrete these enzymes from specialized cells in their guts, including the stomach and pancreas, and salivary glands. The amino acids or sugars released by these extracellular enzymes are then pumped into cells by active transport proteins.

微生物简单直接地将消化酶分泌到周围环境中<ref>{{cite journal | vauthors = Häse CC, Finkelstein RA | title = Bacterial extracellular zinc-containing metalloproteases | journal = Microbiological Reviews | volume = 57 | issue = 4 | pages = 823–37 | date = December 1993 | pmid = 8302217 | pmc = 372940 | doi = 10.1128/MMBR.57.4.823-837.1993 }}</ref><ref>{{cite journal | vauthors = Gupta R, Gupta N, Rathi P | title = Bacterial lipases: an overview of production, purification and biochemical properties | journal = Applied Microbiology and Biotechnology | volume = 64 | issue = 6 | pages = 763–81 | date = June 2004 | pmid = 14966663 | doi = 10.1007/s00253-004-1568-8 | s2cid = 206934353 }}</ref>，而动物必须通过它们肠道(包括胃、胰腺和唾液腺)中的特定细胞分泌这些酶。<ref>{{cite journal | vauthors = Hoyle T | title = The digestive system: linking theory and practice | journal = British Journal of Nursing | volume = 6 | issue = 22 | pages = 1285–91 | year = 1997 | pmid = 9470654 | doi = 10.12968/bjon.1997.6.22.1285 }}</ref>这些细胞外酶释放的氨基酸或糖通过活性转运蛋白被泵入细胞内<ref>{{cite journal | vauthors = Souba WW, Pacitti AJ | title = How amino acids get into cells: mechanisms, models, menus, and mediators | journal = JPEN. Journal of Parenteral and Enteral Nutrition | volume = 16 | issue = 6 | pages = 569–78 | year = 1992 | pmid = 1494216 | doi = 10.1177/0148607192016006569 }}</ref><ref>{{cite journal | vauthors = Barrett MP, Walmsley AR, Gould GW | title = Structure and function of facilitative sugar transporters | journal = Current Opinion in Cell Biology | volume = 11 | issue = 4 | pages = 496–502 | date = August 1999 | pmid = 10449337 | doi = 10.1016/S0955-0674(99)80072-6 }}</ref>。

[[File:Catabolism schematic.svg|thumb|left|upright=1.35|[[蛋白质]]，[[碳水化合物]]和[[脂肪]]分解代谢的简化概述 ]]

===Energy from organic compounds===
有机化合物的能量

{{further|Cellular respiration|Fermentation (biochemistry)|Carbohydrate catabolism|Fat catabolism|Protein catabolism}}

更多信息：细胞呼吸，发酵（生物化学），碳水化合物分解代谢，脂肪分解代谢和蛋白质分解代谢

Carbohydrate catabolism is the breakdown of carbohydrates into smaller units. Carbohydrates are usually taken into cells once they have been digested into [[monosaccharide]]s. Once inside, the major route of breakdown is [[glycolysis]], where sugars such as [[glucose]] and [[fructose]] are converted into [[pyruvic acid|pyruvate]] and some ATP is generated. Pyruvate is an intermediate in several metabolic pathways, but the majority is converted to [[acetyl-CoA]] through aerobic (with oxygen) glycolysis and fed into the [[citric acid cycle]]. Although some more ATP is generated in the citric acid cycle, the most important product is NADH, which is made from NAD+ as the acetyl-CoA is oxidized. This oxidation releases [[carbon dioxide]] as a waste product. In anaerobic conditions, glycolysis produces [[lactic acid|lactate]], through the enzyme [[lactate dehydrogenase]] re-oxidizing NADH to NAD+ for re-use in glycolysis. An alternative route for glucose breakdown is the [[pentose phosphate pathway]], which reduces the coenzyme [[NADPH]] and produces [[pentose]] sugars such as [[ribose]], the sugar component of [[nucleic acid]]s.

Carbohydrate catabolism is the breakdown of carbohydrates into smaller units. Carbohydrates are usually taken into cells once they have been digested into monosaccharides. Once inside, the major route of breakdown is glycolysis, where sugars such as glucose and fructose are converted into pyruvate and some ATP is generated. Pyruvate is an intermediate in several metabolic pathways, but the majority is converted to acetyl-CoA through aerobic (with oxygen) glycolysis and fed into the citric acid cycle. Although some more ATP is generated in the citric acid cycle, the most important product is NADH, which is made from NAD+ as the acetyl-CoA is oxidized. This oxidation releases carbon dioxide as a waste product. In anaerobic conditions, glycolysis produces lactate, through the enzyme lactate dehydrogenase re-oxidizing NADH to NAD+ for re-use in glycolysis. An alternative route for glucose breakdown is the pentose phosphate pathway, which reduces the coenzyme NADPH and produces pentose sugars such as ribose, the sugar component of nucleic acids.

碳水化合物分解代谢是将碳水化合物分解成较小的单位的过程。碳水化合物一旦被消化成单糖，通常就被带入细胞。一旦进入细胞内<ref>{{cite journal | vauthors = Bell GI, Burant CF, Takeda J, Gould GW | title = Structure and function of mammalian facilitative sugar transporters | journal = The Journal of Biological Chemistry | volume = 268 | issue = 26 | pages = 19161–4 | date = September 1993 | pmid = 8366068 }}</ref>，分解的主要途径就是糖酵解，其中糖（例如葡萄糖和果糖）被转化为丙酮酸并生成一些ATP。<ref name=Bouche>{{cite journal | vauthors = Bouché C, Serdy S, Kahn CR, Goldfine AB | title = The cellular fate of glucose and its relevance in type 2 diabetes | journal = Endocrine Reviews | volume = 25 | issue = 5 | pages = 807–30 | date = October 2004 | pmid = 15466941 | doi = 10.1210/er.2003-0026 | df = dmy-all | doi-access = free }}</ref>丙酮酸是几种代谢途径中的中间体，但大多数通过有氧（含氧）糖酵解转化为乙酰辅酶A并进入三羧酸循环。尽管在三羧酸循环中会产生更多的ATP，但最重要的产物是NADH，它是由 NAD + 在乙酰辅酶A被氧化后制成的。这种氧化释放出作为废物的二氧化碳。在厌氧条件下，糖酵解产生乳酸盐，即由乳酸脱氢酶将丙酮酸盐转化为乳酸盐，同时将NADH重新氧化为NAD + 再用于糖酵解。<ref>{{cite journal | vauthors = Alfarouk KO, Verduzco D, Rauch C, Muddathir AK, Adil HH, Elhassan GO, Ibrahim ME, David Polo Orozco J, Cardone RA, Reshkin SJ, Harguindey S | display-authors = 6 | title = Glycolysis, tumor metabolism, cancer growth and dissemination. A new pH-based etiopathogenic perspective and therapeutic approach to an old cancer question | journal = Oncoscience | volume = 1 | issue = 12 | pages = 777–802 | date = 18 December 2014 | pmid = 25621294 | pmc = 4303887 | doi = 10.18632/oncoscience.109 | doi-access = free }}</ref>葡萄糖分解的另一种途径是磷酸戊糖途径，它还原辅酶NADPH并产生戊糖，如核糖（核酸的糖成分）。

Fats are catabolised by [[hydrolysis]] to free fatty acids and glycerol. The glycerol enters glycolysis and the fatty acids are broken down by [[beta oxidation]] to release acetyl-CoA, which then is fed into the citric acid cycle. Fatty acids release more energy upon oxidation than carbohydrates because carbohydrates contain more oxygen in their structures. Steroids are also broken down by some bacteria in a process similar to beta oxidation, and this breakdown process involves the release of significant amounts of acetyl-CoA, propionyl-CoA, and pyruvate, which can all be used by the cell for energy. ''M. tuberculosis'' can also grow on the lipid [[cholesterol]] as a sole source of carbon, and genes involved in the cholesterol use pathway(s) have been validated as important during various stages of the infection lifecycle of ''M. tuberculosis''.

Fats are catabolised by hydrolysis to free fatty acids and glycerol. The glycerol enters glycolysis and the fatty acids are broken down by beta oxidation to release acetyl-CoA, which then is fed into the citric acid cycle. Fatty acids release more energy upon oxidation than carbohydrates because carbohydrates contain more oxygen in their structures. Steroids are also broken down by some bacteria in a process similar to beta oxidation, and this breakdown process involves the release of significant amounts of acetyl-CoA, propionyl-CoA, and pyruvate, which can all be used by the cell for energy. M. tuberculosis can also grow on the lipid cholesterol as a sole source of carbon, and genes involved in the cholesterol use pathway(s) have been validated as important during various stages of the infection lifecycle of M. tuberculosis.

脂肪通过水解作用分解为游离脂肪酸和甘油。甘油进入糖酵解，脂肪酸被 β氧化分解，释放出乙酰辅酶A，然后进入三羧酸循环。脂肪酸在氧化时会释放比碳水化合物更多的能量，因为碳水化合物的结构中含有更多的氧。类固醇也会被一些细菌在类似于 β 氧化的过程中分解，这个分解过程会释放出大量的乙酰辅酶A、丙酰辅酶A和丙酮酸，它们都可以给细胞提供能量。结核杆菌也可以依靠脂质胆固醇这唯一的碳源生长，而且参与胆固醇利用途径的基因已经被证实在结核杆菌感染生命周期的不同阶段都是重要的<ref>{{cite journal | vauthors = Wipperman MF, Sampson NS, Thomas ST | title = Pathogen roid rage: cholesterol utilization by Mycobacterium tuberculosis | journal = Critical Reviews in Biochemistry and Molecular Biology | volume = 49 | issue = 4 | pages = 269–93 | date = 2014 | pmid = 24611808 | pmc = 4255906 | doi = 10.3109/10409238.2014.895700 }}</ref>。

[[Amino acid]]s are either used to synthesize proteins and other biomolecules, or oxidized to [[urea]] and carbon dioxide as a source of energy. The oxidation pathway starts with the removal of the amino group by a [[transaminase]]. The amino group is fed into the [[urea cycle]], leaving a deaminated carbon skeleton in the form of a [[keto acid]]. Several of these keto acids are intermediates in the citric acid cycle, for example the deamination of [[glutamate]] forms α-[[alpha-Ketoglutaric acid|ketoglutarate]]. The [[glucogenic amino acid]]s can also be converted into glucose, through [[gluconeogenesis]] (discussed below).

Amino acids are either used to synthesize proteins and other biomolecules, or oxidized to urea and carbon dioxide as a source of energy. The oxidation pathway starts with the removal of the amino group by a transaminase. The amino group is fed into the urea cycle, leaving a deaminated carbon skeleton in the form of a keto acid. Several of these keto acids are intermediates in the citric acid cycle, for example the deamination of glutamate forms α-ketoglutarate. The glucogenic amino acids can also be converted into glucose, through gluconeogenesis (discussed below).

氨基酸可以用来合成蛋白质和其他生物分子，也可以被氧化成尿素和二氧化碳从而提供能量<ref>{{cite journal | vauthors = Sakami W, Harrington H | title = Amino Acid Metabolism | journal = Annual Review of Biochemistry | volume = 32 | issue = | pages = 355–98 | year = 1963 | pmid = 14144484 | doi = 10.1146/annurev.bi.32.070163.002035 }}</ref>。氧化途径从转氨酶去除氨基酸上的氨基开始。氨基进入尿素循环，留下酮酸形式的脱氨基碳骨架。其中一些酮酸是三羧酸循环的中间产物，例如谷氨酸的脱氨反应形成 α- 酮戊二酸<ref>{{cite journal | vauthors = Brosnan JT | title = Glutamate, at the interface between amino acid and carbohydrate metabolism | journal = The Journal of Nutrition | volume = 130 | issue = 4S Suppl | pages = 988S–90S | date = April 2000 | pmid = 10736367 | doi = 10.1093/jn/130.4.988S | doi-access = free }}</ref>。葡萄糖原氨基酸也可以通过糖异生作用转化为葡萄糖(具体内容见下文)<ref>{{cite journal | vauthors = Young VR, Ajami AM | title = Glutamine: the emperor or his clothes? | journal = The Journal of Nutrition | volume = 131 | issue = 9 Suppl | pages = 2449S–59S; discussion 2486S–7S | date = September 2001 | pmid = 11533293 | doi = 10.1093/jn/131.9.2449S | doi-access = free }}</ref>。

==Energy transformations==
能量转换

===Oxidative phosphorylation===
氧化磷酸化

{{further|Oxidative phosphorylation|Chemiosmosis|Mitochondrion}}

更多信息：氧化磷酸化，化学渗透和线粒体

In oxidative phosphorylation, the electrons removed from organic molecules in areas such as the protagon acid cycle are transferred to oxygen and the energy released is used to make ATP. This is done in [[eukaryote]]s by a series of proteins in the membranes of mitochondria called the [[electron transport chain]]. In [[prokaryote]]s, these proteins are found in the cell's [[bacterial cell structure|inner membrane]]. These proteins use the energy released from passing electrons from [[reducing agent|reduced]] molecules like NADH onto [[oxygen]] to pump [[proton]]s across a membrane.

In oxidative phosphorylation, the electrons removed from organic molecules in areas such as the protagon acid cycle are transferred to oxygen and the energy released is used to make ATP. This is done in eukaryotes by a series of proteins in the membranes of mitochondria called the electron transport chain. In prokaryotes, these proteins are found in the cell's inner membrane. These proteins use the energy released from passing electrons from reduced molecules like NADH onto oxygen to pump protons across a membrane.

氧化磷酸化中，通过如柠檬酸循环等代谢途径，电子从被消化吸收的食物分子上转移到氧气上，并将产生的能量以ATP的方式储存起来。在真核生物中，这一过程是通过线粒体膜上的一系列膜蛋白来完成的，被称为电子传递链。而在原核生物中，这些蛋白质存在于细胞的内膜中。<ref>{{cite journal | vauthors = Hosler JP, Ferguson-Miller S, Mills DA | title = Energy transduction: proton transfer through the respiratory complexes | journal = Annual Review of Biochemistry | volume = 75 | issue = | pages = 165–87 | year = 2006 | pmid = 16756489 | pmc = 2659341 | doi = 10.1146/annurev.biochem.75.062003.101730 }}</ref>这些蛋白质利用电子从还原性分子(如NADH)传递到氧气所释放的能量来泵送质子穿过细胞膜<ref>{{cite journal | vauthors = Schultz BE, Chan SI | title = Structures and proton-pumping strategies of mitochondrial respiratory enzymes | journal = Annual Review of Biophysics and Biomolecular Structure | volume = 30 | issue = | pages = 23–65 | year = 2001 | pmid = 11340051 | doi = 10.1146/annurev.biophys.30.1.23 | url = https://authors.library.caltech.edu/1623/1/SCHarbbs01.pdf }}</ref>。

[[File:ATPsyn.gif|thumb|right|[[ATP合成酶]]的作用机制。ATP 显示为红色，ADP 和磷酸显示为粉红色，转柄亚基显示为黑色]]

Pumping protons out of the mitochondria creates a proton [[diffusion|concentration difference]] across the membrane and generates an [[electrochemical gradient]]. This force drives protons back into the mitochondrion through the base of an enzyme called [[ATP synthase]]. The flow of protons makes the stalk subunit rotate, causing the [[active site]] of the synthase domain to change shape and phosphorylate [[adenosine diphosphate]] – turning it into ATP.

Pumping protons out of the mitochondria creates a proton concentration difference across the membrane and generates an electrochemical gradient. This force drives protons back into the mitochondrion through the base of an enzyme called ATP synthase. The flow of protons makes the stalk subunit rotate, causing the active site of the synthase domain to change shape and phosphorylate adenosine diphosphate– turning it into ATP.

将质子泵出线粒体，会在膜上形成质子浓度差，产生电化学梯度。<ref>{{cite journal | vauthors = Capaldi RA, Aggeler R | title = Mechanism of the F(1)F(0)-type ATP synthase, a biological rotary motor | journal = Trends in Biochemical Sciences | volume = 27 | issue = 3 | pages = 154–60 | date = March 2002 | pmid = 11893513 | doi = 10.1016/S0968-0004(01)02051-5 }}</ref>这种力量促使质子通过ATP合成酶的基座回到线粒体中。质子的流动使柄亚基旋转，从而改变合成酶域的活性位点的形状，使二磷酸腺苷磷酸化--变成ATP<ref name=Dimroth/>。

===Energy from inorganic compounds===
无机化合物的能量

{{further|Microbial metabolism|Nitrogen cycle}}

更多信息：微生物代谢和氮循环

[[Chemolithotroph]]y is a type of metabolism found in [[prokaryote]]s where energy is obtained from the oxidation of [[inorganic compound]]s. These organisms can use [[hydrogen]], reduced [[sulfur]] compounds (such as [[sulfide]], [[hydrogen sulfide]] and [[thiosulfate]]),<ref name=Physiology1/> [[Iron(II) oxide|ferrous iron (FeII)]] or [[ammonia]] as sources of reducing power and they gain energy from the oxidation of these compounds with electron acceptors such as [[oxygen]] or [[nitrite]]. These microbial processes are important in global [[biogeochemical cycle]]s such as [[acetogenesis]], [[nitrification]] and [[denitrification]] and are critical for [[fertility (soil)|soil fertility]].

Chemolithotrophy is a type of metabolism found in prokaryotes where energy is obtained from the oxidation of inorganic compounds. These organisms can use hydrogen, reduced sulfur compounds (such as sulfide, hydrogen sulfide and thiosulfate), or ammonia as sources of reducing power and they gain energy from the oxidation of these compounds with electron acceptors such as oxygen or nitrite. These microbial processes are important in global biogeochemical cycles such as acetogenesis, nitrification and denitrification and are critical for soil fertility.

化能无机营养是在原核生物中发现的一种新陈代谢，其能量来自于无机化合物的氧化。这些生物可以利用氢气、<ref>{{cite journal | vauthors = Friedrich B, Schwartz E | title = Molecular biology of hydrogen utilization in aerobic chemolithotrophs | journal = Annual Review of Microbiology | volume = 47 | issue = | pages = 351–83 | year = 1993 | pmid = 8257102 | doi = 10.1146/annurev.mi.47.100193.002031 }}</ref> 还原硫化合物(如硫化物、硫化氢和硫代硫酸酯<ref>{{cite journal | vauthors = Weber KA, Achenbach LA, Coates JD | title = Microorganisms pumping iron: anaerobic microbial iron oxidation and reduction | journal = Nature Reviews. Microbiology | volume = 4 | issue = 10 | pages = 752–64 | date = October 2006 | pmid = 16980937 | doi = 10.1038/nrmicro1490 | url = https://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=1203&context=bioscifacpub | s2cid = 8528196 }}</ref>)或氨<ref>{{cite journal | vauthors = Jetten MS, Strous M, van de Pas-Schoonen KT, Schalk J, van Dongen UG, van de Graaf AA, Logemann S, Muyzer G, van Loosdrecht MC, Kuenen JG | display-authors = 6 | title = The anaerobic oxidation of ammonium | journal = FEMS Microbiology Reviews | volume = 22 | issue = 5 | pages = 421–37 | date = December 1998 | pmid = 9990725 | doi = 10.1111/j.1574-6976.1998.tb00379.x | doi-access = free }}</ref>作为还原力的来源，它们从这些化合物与氧或亚硝酸盐等电子接受体的氧化作用中获得能量。这些微生物过程<ref>{{cite journal | vauthors = Simon J | title = Enzymology and bioenergetics of respiratory nitrite ammonification | journal = FEMS Microbiology Reviews | volume = 26 | issue = 3 | pages = 285–309 | date = August 2002 | pmid = 12165429 | doi = 10.1111/j.1574-6976.2002.tb00616.x | doi-access = free }}</ref>在全球生物地球化学循环（如乙酰化、硝化和反硝化）中非常重要，对土壤肥力也很关键<ref>{{cite journal | vauthors = Conrad R | title = Soil microorganisms as controllers of atmospheric trace gases (H2, CO, CH4, OCS, N2O, and NO) | journal = Microbiological Reviews | volume = 60 | issue = 4 | pages = 609–40 | date = December 1996 | pmid = 8987358 | pmc = 239458 | doi = 10.1128/MMBR.60.4.609-640.1996 }}</ref><ref>{{cite journal | vauthors = Barea JM, Pozo MJ, Azcón R, Azcón-Aguilar C | title = Microbial co-operation in the rhizosphere | journal = Journal of Experimental Botany | volume = 56 | issue = 417 | pages = 1761–78 | date = July 2005 | pmid = 15911555 | doi = 10.1093/jxb/eri197 | doi-access = free }}</ref>。

===Energy from light===
光能
{{further|Phototroph|Photophosphorylation|Chloroplast}}

更多信息：光养，光磷酸化和叶绿体

The energy in sunlight is captured by [[plant]]s, [[cyanobacteria]], [[purple bacteria]], [[green sulfur bacteria]] and some [[protist]]s. This process is often coupled to the conversion of carbon dioxide into organic compounds, as part of photosynthesis, which is discussed below. The energy capture and carbon fixation systems can however operate separately in prokaryotes, as purple bacteria and green sulfur bacteria can use sunlight as a source of energy, while switching between carbon fixation and the fermentation of organic compounds.

The energy in sunlight is captured by plants, cyanobacteria, purple bacteria, green sulfur bacteria and some protists. This process is often coupled to the conversion of carbon dioxide into organic compounds, as part of photosynthesis, which is discussed below. The energy capture and carbon fixation systems can however operate separately in prokaryotes, as purple bacteria and green sulfur bacteria can use sunlight as a source of energy, while switching between carbon fixation and the fermentation of organic compounds.

阳光中的能量被植物、蓝藻、紫细菌、绿硫细菌和一些原生生物所吸收。这个过程通常与二氧化碳转化为有机化合物相结合，这是光合作用的一部分，下文将对此进行讨论。然而，原核生物的能量捕获和碳固定系统可以单独运作，因为紫色细菌和绿硫细菌可以利用阳光作为能源，同时在碳固定和有机化合物发酵之间转换<ref>{{cite journal | vauthors = van der Meer MT, Schouten S, Bateson MM, Nübel U, Wieland A, Kühl M, de Leeuw JW, Sinninghe Damsté JS, Ward DM | display-authors = 6 | title = Diel variations in carbon metabolism by green nonsulfur-like bacteria in alkaline siliceous hot spring microbial mats from Yellowstone National Park | journal = Applied and Environmental Microbiology | volume = 71 | issue = 7 | pages = 3978–86 | date = July 2005 | pmid = 16000812 | pmc = 1168979 | doi = 10.1128/AEM.71.7.3978-3986.2005 }}</ref><ref>{{cite journal | vauthors = Tichi MA, Tabita FR | title = Interactive control of Rhodobacter capsulatus redox-balancing systems during phototrophic metabolism | journal = Journal of Bacteriology | volume = 183 | issue = 21 | pages = 6344–54 | date = November 2001 | pmid = 11591679 | pmc = 100130 | doi = 10.1128/JB.183.21.6344-6354.2001 }}</ref>。

In many organisms, the capture of solar energy is similar in principle to oxidative phosphorylation, as it involves the storage of energy as a proton concentration gradient. This proton motive force then drives ATP synthesis. The electrons needed to drive this electron transport chain come from light-gathering proteins called [[photosynthetic reaction centre]]s. Reaction centers are classed into two types depending on the nature of [[photosynthetic pigment]] present, with most photosynthetic bacteria only having one type, while plants and cyanobacteria have two.

In many organisms, the capture of solar energy is similar in principle to oxidative phosphorylation, as it involves the storage of energy as a proton concentration gradient. This proton motive force then drives ATP synthesis. The electrons needed to drive this electron transport chain come from light-gathering proteins called photosynthetic reaction centres. Reaction centers are classed into two types depending on the nature of photosynthetic pigment present, with most photosynthetic bacteria only having one type, while plants and cyanobacteria have two.

在许多生物体中，太阳能的获取在原理上类似于氧化磷酸化，因为它涉及到以质子浓度梯度的形式储存能量。这种质子动力驱动 ATP 的合成<ref>{{cite book |last1=Alberts|first1=Bruce|last2=Johnson|first2=Alexander|last3=Lewis|first3=Julian|last4=Raff|first4=Martin|last5=Roberts|first5=Keith|last6=Walter|first6=Peter | name-list-style = vanc |date=2002|chapter =Energy Conversion: Mitochondria and Chloroplasts|url=https://www.ncbi.nlm.nih.gov/books/NBK21063/|title =Molecular Biology of the Cell. 4th edition|language=en}}</ref> 。驱动这种电子传递链所需的电子来自于聚光蛋白质，这种蛋白质被叫做光合反应中心。根据存在的光合色素的性质，反应中心分为两种类型。大多数光合细菌只有一种类型，而植物和蓝藻有两种类型<ref>{{cite journal | vauthors = Allen JP, Williams JC | title = Photosynthetic reaction centers | journal = FEBS Letters | volume = 438 | issue = 1–2 | pages = 5–9 | date = October 1998 | pmid = 9821949 | doi = 10.1016/S0014-5793(98)01245-9 | s2cid = 21596537 }}</ref>。

In plants, algae, and cyanobacteria, [[photosystem|photosystem II]] uses light energy to remove electrons from water, releasing oxygen as a waste product. The electrons then flow to the [[cytochrome b6f complex]], which uses their energy to pump protons across the [[thylakoid]] membrane in the [[chloroplast]]. These protons move back through the membrane as they drive the ATP synthase, as before. The electrons then flow through [[photosystem|photosystem I]] and can then either be used to reduce the coenzyme NADP+.f. These cooenzyme can be used in the [[Calvin cycle]], which is discussed below, or recycled for further ATP generation.

In plants, algae, and cyanobacteria, photosystem II uses light energy to remove electrons from water, releasing oxygen as a waste product. The electrons then flow to the cytochrome b6f complex, which uses their energy to pump protons across the thylakoid membrane in the chloroplast. These protons move back through the membrane as they drive the ATP synthase, as before. The electrons then flow through photosystem I and can then either be used to reduce the coenzyme NADP + .fThese cooenzyme can be used in the Calvin cycle, which is discussed below, or recycled for further ATP generation.

在植物、藻类和蓝藻中，光系统 II 利用光能将电子从水中移走，释放出氧气。然后电子流向细胞色素b6f蛋白复合体，后者利用它们的能量穿过叶绿体中的类囊体膜，泵入质子<ref name=Nelson2004/>。这些质子在驱动ATP合成酶时通过膜向后移动，就像之前一样。然后电子流经光系统I，可以用来减少辅酶NADP + <ref>{{cite journal | vauthors = Munekage Y, Hashimoto M, Miyake C, Tomizawa K, Endo T, Tasaka M, Shikanai T | title = Cyclic electron flow around photosystem I is essential for photosynthesis | journal = Nature | volume = 429 | issue = 6991 | pages = 579–82 | date = June 2004 | pmid = 15175756 | doi = 10.1038/nature02598 | bibcode = 2004Natur.429..579M | s2cid = 4421776 }}</ref>。这些辅酶可用于[[卡尔文循环]](下文将对此进行讨论)，或被循环用于进一步生成ATP。

==Anabolism==
合成代谢

{{further|Anabolism}}

更多信息：合成代谢

'''Anabolism''' is the set of constructive metabolic processes where the energy released by catabolism is used to synthesize complex molecules. In general, the complex molecules that make up cellular structures are constructed step-by-step from small and simple precursors. Anabolism involves three basic stages. First, the production of precursors such as [[amino acid]]s, [[monosaccharide]]s, [[Terpenoid|isoprenoids]] and [[nucleotide]]s, secondly, their activation into reactive forms using energy from ATP, and thirdly, the assembly of these precursors into complex molecules such as [[protein]]s, [[polysaccharide]]s, [[lipid]]s and [[nucleic acid]]s.

Anabolism is the set of constructive metabolic processes where the energy released by catabolism is used to synthesize complex molecules. In general, the complex molecules that make up cellular structures are constructed step-by-step from small and simple precursors. Anabolism involves three basic stages. First, the production of precursors such as amino acids, monosaccharides, isoprenoids and nucleotides, secondly, their activation into reactive forms using energy from ATP, and thirdly, the assembly of these precursors into complex molecules such as proteins, polysaccharides, lipids and nucleic acids.

合成代谢是一系列建设性的新陈代谢过程，在这一系列过程中分解代谢所释放的能量被用来合成复杂的分子。一般来说，组成细胞结构的复杂分子是由小而简单的前体逐步构成的。合成代谢包括三个基本阶段。首先是氨基酸、单糖、异戊二烯和核苷酸等前体的产生，其次是利用ATP产生的能量将它们活化成活性形式，第三是将这些前体组装成复杂的分子，如蛋白质、多糖、脂质和核酸<ref name=":0">{{cite web|last=Mandal|first=Ananya| name-list-style = vanc |date=2009-11-26|title=What is Anabolism?|url=https://www.news-medical.net/life-sciences/What-is-Anabolism.aspx|access-date=2020-07-04|website=News-Medical.net|language=en}}</ref>。

Anabolism in organisms can be different according to the source of constructed molecules in their cells. [[Autotroph]]s such as plants can construct the complex organic molecules in cells such as polysaccharides and proteins from simple molecules like [[carbon dioxide]] and water. [[Heterotroph]]s, on the other hand, require a source of more complex substances, such as monosaccharides and amino acids, to produce these complex molecules. Organisms can be further classified by ultimate source of their energy: photoautotrophs and photoheterotrophs obtain energy from light, whereas chemoautotrophs and chemoheterotrophs obtain energy from inorganic oxidation reactions.

Anabolism in organisms can be different according to the source of constructed molecules in their cells. Autotrophs such as plants can construct the complex organic molecules in cells such as polysaccharides and proteins from simple molecules like carbon dioxide and water. Heterotrophs, on the other hand, require a source of more complex substances, such as monosaccharides and amino acids, to produce these complex molecules. Organisms can be further classified by ultimate source of their energy: photoautotrophs and photoheterotrophs obtain energy from light, whereas chemoautotrophs and chemoheterotrophs obtain energy from inorganic oxidation reactions.

生物体的合成代谢根据其细胞中构建分子的来源而有所不同。植物等自养生物可以在细胞中利用二氧化碳和水等简单分子中构建复杂的有机分子（如多糖和蛋白质）。而异养生物则需要更复杂的物质来源（如单糖和氨基酸）才能产生这些复杂的分子。生物可以根据其能量的最终来源进一步分类: 光自养生物和光异养生物从光中获得能量，而化能自养生物和化能异养生物从无机氧化反应中获得能量<ref name=":0" />
。

===Carbon fixation===
碳固定
{{further|Photosynthesis|Carbon fixation|Chemosynthesis}}

更多信息：光合作用，碳固定和化学合成

[[File:Plagiomnium affine laminazellen.jpeg|thumb|含叶绿体（绿色）的植物细胞（以紫色壁为边界），叶绿体是光合作用的部位]]

Photosynthesis is the synthesis of carbohydrates from sunlight and [[carbon dioxide]] (CO2). In plants, cyanobacteria and algae, oxygenic photosynthesis splits water, with oxygen produced as a waste product. This process uses the ATP and NADPH produced by the [[photosynthetic reaction centre]]s, as described above, to convert CO2 into [[glycerate 3-phosphate]], which can then be converted into glucose. This carbon-fixation reaction is carried out by the enzyme [[RuBisCO]] as part of the [[Calvin cycle|Calvin – Benson cycle]]. Three types of photosynthesis occur in plants, [[C3 carbon fixation]], [[C4 carbon fixation]] and [[Crassulacean acid metabolism|CAM photosynthesis]]. These differ by the route that carbon dioxide takes to the Calvin cycle, with C3 plants fixing CO2 directly, while C4 and CAM photosynthesis incorporate the CO2 into other compounds first, as adaptations to deal with intense sunlight and dry conditions.

Photosynthesis is the synthesis of carbohydrates from sunlight and carbon dioxide (CO2). In plants, cyanobacteria and algae, oxygenic photosynthesis splits water, with oxygen produced as a waste product. This process uses the ATP and NADPH produced by the photosynthetic reaction centres, as described above, to convert CO2 into glycerate 3-phosphate, which can then be converted into glucose. This carbon-fixation reaction is carried out by the enzyme RuBisCO as part of the Calvin – Benson cycle.[64] Three types of photosynthesis occur in plants, C3 carbon fixation, C4 carbon fixation and CAM photosynthesis. These differ by the route that carbon dioxide takes to the Calvin cycle, with C3 plants fixing CO2 directly, while C4 and CAM photosynthesis incorporate the CO2 into other compounds first, as adaptations to deal with intense sunlight and dry conditions.

光合作用就是依靠阳光和二氧化碳(CO2)合成碳水化合物。在植物中，蓝细菌和藻类的含氧光合作用使水分解，排出氧气。如前所述，这一过程利用光合反应中心产生的ATP和NADPH将CO2转化为三磷酸甘油酯，然后再转化为葡萄糖。这个固碳反应作为卡尔文-本森Calvin – Benson 循环的一部分是在RuBisCO酶的催化下进行的<ref>{{cite journal | vauthors = Miziorko HM, Lorimer GH | title = Ribulose-1,5-bisphosphate carboxylase-oxygenase | journal = Annual Review of Biochemistry | volume = 52 | issue = | pages = 507–35 | year = 1983 | pmid = 6351728 | doi = 10.1146/annurev.bi.52.070183.002451 }}</ref>。植物有三种类型的光合作用:C3固碳、C4固碳和CAM光合作用。它们的不同之处在于二氧化碳进入卡尔文循环的路径不同，C3植物直接固定二氧化碳，而C4和CAM植物首先将二氧化碳吸收到其他化合物中，以适应强烈的阳光和干燥的环境<ref>{{cite journal | vauthors = Dodd AN, Borland AM, Haslam RP, Griffiths H, Maxwell K | title = Crassulacean acid metabolism: plastic, fantastic | journal = Journal of Experimental Botany | volume = 53 | issue = 369 | pages = 569–80 | date = April 2002 | pmid = 11886877 | doi = 10.1093/jexbot/53.369.569 | doi-access = free }}</ref>。

In photosynthetic [[prokaryote]]s the mechanisms of carbon fixation are more diverse. Here, carbon dioxide can be fixed by the Calvin – Benson cycle, a [[Reverse Krebs cycle|reversed citric acid]] cycle, or the carboxylation of acetyl-CoA. Prokaryotic [[Chemotroph|chemoautotrophs]] also fix CO2 through the Calvin–Benson cycle, but use energy from inorganic compounds to drive the reaction.

In photosynthetic prokaryotes the mechanisms of carbon fixation are more diverse. Here, carbon dioxide can be fixed by the Calvin– Benson cycle, a reversed citric acid cycle, or the carboxylation of acetyl-CoA. Prokaryotic chemoautotrophs also fix CO2 through the Calvin–Benson cycle, but use energy from inorganic compounds to drive the reaction.

在能够光合作用的原核生物中，碳固定的机制更加多样。对它们而言，二氧化碳可以通过Calvin– Benson循环、反向三羧酸循环<ref>{{cite journal | vauthors = Hügler M, Wirsen CO, Fuchs G, Taylor CD, Sievert SM | title = Evidence for autotrophic CO2 fixation via the reductive tricarboxylic acid cycle by members of the epsilon subdivision of proteobacteria | journal = Journal of Bacteriology | volume = 187 | issue = 9 | pages = 3020–7 | date = May 2005 | pmid = 15838028 | pmc = 1082812 | doi = 10.1128/JB.187.9.3020-3027.2005 }}</ref>或乙酰辅酶A的羧化作用得到固定。原核化能自养生物也通过Calvin– Benson环固定CO 2 <ref>{{cite journal | vauthors = Strauss G, Fuchs G | title = Enzymes of a novel autotrophic CO2 fixation pathway in the phototrophic bacterium Chloroflexus aurantiacus, the 3-hydroxypropionate cycle | journal = European Journal of Biochemistry | volume = 215 | issue = 3 | pages = 633–43 | date = August 1993 | pmid = 8354269 | doi = 10.1111/j.1432-1033.1993.tb18074.x }}</ref><ref>{{cite journal | vauthors = Wood HG | title = Life with CO or CO2 and H2 as a source of carbon and energy | journal = FASEB Journal | volume = 5 | issue = 2 | pages = 156–63 | date = February 1991 | pmid = 1900793 | doi = 10.1096/fasebj.5.2.1900793 | s2cid = 45967404 }}</ref>，但它们利用无机化合物的能量来驱动反应<ref>{{cite journal | vauthors = Shively JM, van Keulen G, Meijer WG | title = Something from almost nothing: carbon dioxide fixation in chemoautotrophs | journal = Annual Review of Microbiology | volume = 52 | issue = | pages = 191–230 | year = 1998 | pmid = 9891798 | doi = 10.1146/annurev.micro.52.1.191 }}</ref>。

===Carbohydrates and glycans===
碳水化合物和聚糖
{{further|Gluconeogenesis|Glyoxylate cycle|Glycogenesis|Glycosylation}}

更多信息：糖异生，乙醛酸循环，糖异生和糖基化

In carbohydrate anabolism, simple organic acids can be converted into [[monosaccharide]]s such as [[glucose]] and then used to assemble [[polysaccharide]]s such as [[starch]]. The generation of [[glucose]] from compounds like [[pyruvate]], [[lactic acid|lactate]], [[glycerol]], [[glycerate 3-phosphate]] and [[amino acid]]s is called [[gluconeogenesis]]. Gluconeogenesis converts pyruvate to [[glucose-6-phosphate]] through a series of intermediates, many of which are shared with [[glycolysis]]. However, this pathway is not simply [[glycolysis]] run in reverse, as several steps are catalyzed by non-glycolytic enzymes. This is important as it allows the formation and breakdown of glucose to be regulated separately, and prevents both pathways from running simultaneously in a [[futile cycle]].

In carbohydrate anabolism, simple organic acids can be converted into monosaccharides such as glucose and then used to assemble polysaccharides such as starch. The generation of glucose from compounds like pyruvate, lactate, glycerol, glycerate 3-phosphate and amino acids is called gluconeogenesis. Gluconeogenesis converts pyruvate to glucose-6-phosphate through a series of intermediates, many of which are shared with glycolysis.However, this pathway is not simply glycolysis run in reverse, as several steps are catalyzed by non-glycolytic enzymes. This is important as it allows the formation and breakdown of glucose to be regulated separately, and prevents both pathways from running simultaneously in a futile cycle.

在碳水化合物合成代谢过程中，简单的有机酸可转化为葡萄糖等单糖，再用于合成淀粉等多糖。由丙酮酸、乳酸、甘油、3-磷酸甘油酸和氨基酸等化合物生成葡萄糖称为葡萄糖异生。糖异生作用通过一系列中间产物将丙酮酸转化为葡萄糖-6-磷酸，其中许多中间产物与糖酵解过程相同<ref name=Bouche/>。然而，这一途径并不是简单的糖酵解逆向运行，因为有几个步骤是由非糖酵解酶催化的。这很重要，因为它使得葡萄糖的形成和分解可以分别被调节，而且防止了两条途径在无效循环中同时运行<ref>{{cite journal | vauthors = Boiteux A, Hess B | title = Design of glycolysis | journal = Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences | volume = 293 | issue = 1063 | pages = 5–22 | date = June 1981 | pmid = 6115423 | doi = 10.1098/rstb.1981.0056 | doi-access = free | bibcode = 1981RSPTB.293....5B }}</ref><ref>{{cite journal | vauthors = Pilkis SJ, el-Maghrabi MR, Claus TH | title = Fructose-2,6-bisphosphate in control of hepatic gluconeogenesis. From metabolites to molecular genetics | journal = Diabetes Care | volume = 13 | issue = 6 | pages = 582–99 | date = June 1990 | pmid = 2162755 | doi = 10.2337/diacare.13.6.582 | s2cid = 44741368 }}</ref>。

Although fat is a common way of storing energy, in [[vertebrate]]s such as humans the [[fatty acid]]s in these stores cannot be converted to glucose through [[gluconeogenesis]] as these organisms cannot convert acetyl-CoA into [[pyruvate]]; plants do, but animals do not, have the necessary enzymatic machinery. As a result, after long-term starvation, vertebrates need to produce [[Ketone body|ketone bodies]] from fatty acids to replace glucose in tissues such as the brain that cannot metabolize fatty acids.In other organisms such as plants and bacteria, this metabolic problem is solved using the [[glyoxylate cycle]], which bypasses the [[decarboxylation]] step in the citric acid cycle and allows the transformation of acetyl-CoA to [[oxaloacetate]], where it can be used for the production of glucose. Other than fat, glucose is stored in most tissues, as an energy resource available within the tissue through glycogenesis which was usually being used to maintained glucose level in blood.

Although fat is a common way of storing energy, in vertebrates such as humans the fatty acids in these stores cannot be converted to glucose through gluconeogenesis as these organisms cannot convert acetyl-CoA into pyruvate; plants do, but animals do not, have the necessary enzymatic machinery. As a result, after long-term starvation, vertebrates need to produce ketone bodies from fatty acids to replace glucose in tissues such as the brain that cannot metabolize fatty acids. In other organisms such as plants and bacteria, this metabolic problem is solved using the glyoxylate cycle, which bypasses the decarboxylation step in the citric acid cycle and allows the transformation of acetyl-CoA to oxaloacetate, where it can be used for the production of glucose. Other than fat, glucose is stored in most tissues, as an energy resource available within the tissue through glycogenesis which was usually being used to maintained glucose level in blood.

虽然脂肪是储存能量的一种常见方式，但在脊椎动物(如人类)体内储存的脂肪酸不能通过葡萄糖异生作用转化为葡萄糖，因为这些生物不能将乙酰辅酶A转化为丙酮酸;植物有必要的酶催化机制，而动物没有<ref name=Ensign>{{cite journal | vauthors = Ensign SA | title = Revisiting the glyoxylate cycle: alternate pathways for microbial acetate assimilation | journal = Molecular Microbiology | volume = 61 | issue = 2 | pages = 274–6 | date = July 2006 | pmid = 16856935 | doi = 10.1111/j.1365-2958.2006.05247.x | s2cid = 39986630 }}</ref>。因此，在长期饥饿后，脊椎动物需要从脂肪酸中产生酮体，以取代大脑等不能代谢脂肪酸的组织中的葡萄糖。在其他生物体如植物和细菌中，这个代谢问题是靠乙醛酸循环来解决的<ref>{{cite journal | vauthors = Finn PF, Dice JF | title = Proteolytic and lipolytic responses to starvation | journal = Nutrition | volume = 22 | issue = 7–8 | pages = 830–44 | year = 2006 | pmid = 16815497 | doi = 10.1016/j.nut.2006.04.008 }}</ref> 。乙醛酸循环绕过三羧酸循环中的脱羧步骤，并将乙酰辅酶a转化为草酰乙酸，在那里它可以用来生产葡萄糖。除了脂肪<ref name=Ensign/><ref name=Kornberg>{{cite journal | vauthors = Kornberg HL, Krebs HA | title = Synthesis of cell constituents from C2-units by a modified tricarboxylic acid cycle | journal = Nature | volume = 179 | issue = 4568 | pages = 988–91 | date = May 1957 | pmid = 13430766 | doi = 10.1038/179988a0 | s2cid = 40858130 | bibcode = 1957Natur.179..988K }}</ref>，葡萄糖也作为一种能量资源储存在大多数组织中，一般会通过它的糖化来维持血液中的葡萄糖水平<ref>{{cite journal|last1=Evans|first1=Rhys D.|last2=Heather|first2=Lisa C. | name-list-style = vanc |date=June 2016|title=Metabolic pathways and abnormalities|journal=Surgery (Oxford)|volume=34|issue=6|pages=266–272|doi=10.1016/j.mpsur.2016.03.010|issn=0263-9319|url=https://ora.ox.ac.uk/objects/uuid:84c0a8e7-38e9-4de2-ba19-9f129a07987a}}</ref> 。

Polysaccharides and [[glycan]]s are made by the sequential addition of monosaccharides by [[glycosyltransferase]] from a reactive sugar-phosphate donor such as [[uridine diphosphate glucose]] (UDP-Glc) to an acceptor [[hydroxyl]] group on the growing polysaccharide. As any of the [[hydroxyl]] groups on the ring of the substrate can be acceptors, the polysaccharides produced can have straight or branched structures. The polysaccharides produced can have structural or metabolic functions themselves, or be transferred to lipids and proteins by enzymes called [[oligosaccharyltransferase]]s.

Polysaccharides and glycans are made by the sequential addition of monosaccharides by glycosyltransferase from a reactive sugar-phosphate donor such as uridine diphosphate glucose (UDP-Glc) to an acceptor hydroxyl group on the growing polysaccharide. As any of the hydroxyl groups on the ring of the substrate can be acceptors, the polysaccharides produced can have straight or branched structures. The polysaccharides produced can have structural or metabolic functions themselves, or be transferred to lipids and proteins by enzymes called oligosaccharyltransferases.

多糖和聚糖是在糖基转移酶作用下，将单糖从活性糖-磷酸盐供体（如尿苷二磷酸葡萄糖(UDP-Glc)）依次加入到生长中的多糖的受体羟基上形成的。由于底物环上的任何羟基都可以作为受体，所以产生的多糖会有直链或支链结构<ref>{{cite book |last1=Freeze|first1=Hudson H. | name-list-style = vanc | chapter =Glycosylation Precursors|date=2015|url=http://www.ncbi.nlm.nih.gov/books/NBK453043/| title = Essentials of Glycobiology|editor-last=Varki|editor-first=Ajit|edition=3rd|place=Cold Spring Harbor (NY)|publisher=Cold Spring Harbor Laboratory Press|pmid=28876856|access-date=2020-07-08|last2=Hart|first2=Gerald W.|last3=Schnaar|first3=Ronald L.|doi=10.1101/glycobiology.3e.005 |doi-broken-date=1 November 2020 |editor2-last=Cummings|editor2-first=Richard D.|editor3-last=Esko|editor3-first=Jeffrey D.|editor4-last=Stanley|editor4-first=Pamela }}</ref>。产生的多糖本身具有结构或代谢功能，还可以通过低聚糖转移酶转移到脂质和蛋白质中<ref>{{cite journal | vauthors = Opdenakker G, Rudd PM, Ponting CP, Dwek RA | title = Concepts and principles of glycobiology | journal = FASEB Journal | volume = 7 | issue = 14 | pages = 1330–7 | date = November 1993 | pmid = 8224606 | doi = 10.1096/fasebj.7.14.8224606 | s2cid = 10388991 }}</ref><ref>{{cite journal | vauthors = McConville MJ, Menon AK | title = Recent developments in the cell biology and biochemistry of glycosylphosphatidylinositol lipids (review) | journal = Molecular Membrane Biology | volume = 17 | issue = 1 | pages = 1–16 | year = 2000 | pmid = 10824734 | doi = 10.1080/096876800294443 | doi-access = free }}</ref>。

===Fatty acids, isoprenoids and sterol===

脂肪酸，类异戊二烯和固醇

{{further|Fatty acid synthesis|Steroid metabolism}}

更多信息：脂肪酸合成和类固醇代谢

[[File:Sterol synthesis.svg|thumb|right|upright=1.6|具有中间体[[异戊烯基焦磷酸酯]]（IPP），[[二甲基烯丙基焦磷酸酯]]（DMAPP），[[香叶基焦磷酸酯]]（GPP）和[[角鲨烯的类固醇]]合成途径的简化版本。为了清晰起见，省略了一些中间步骤。]]

Fatty acids are made by [[fatty acid synthase]]s that polymerize and then reduce acetyl-CoA units. The acyl chains in the fatty acids are extended by a cycle of reactions that add the acyl group, reduce it to an alcohol, [[dehydration reaction|dehydrate]] it to an [[alkene]] group and then reduce it again to an [[alkane]] group. The enzymes of fatty acid biosynthesis are divided into two groups: in animals and fungi, all these fatty acid synthase reactions are carried out by a single multifunctional type I protein, while in plant [[plastid]]s and bacteria separate type II enzymes perform each step in the pathway.

Fatty acids are made by fatty acid synthases that polymerize and then reduce acetyl-CoA units. The acyl chains in the fatty acids are extended by a cycle of reactions that add the acyl group, reduce it to an alcohol, dehydrate it to an alkene group and then reduce it again to an alkane group. The enzymes of fatty acid biosynthesis are divided into two groups: in animals and fungi, all these fatty acid synthase reactions are carried out by a single multifunctional type I protein, while in plant plastids and bacteria separate type II enzymes perform each step in the pathway.

脂肪酸是由脂肪酸合成酶聚合并还原乙酰辅酶A单元制成的。脂肪酸中的酰基链通过一些反应的循环得以延伸，这些反应包括:添加酰基，将其还原为醇，脱水成烯烃基团，然后再还原为烷烃基团。脂肪酸生物合成的酶可以分为两类：在动物和真菌中，所有脂肪酸合成酶的反应都是由单一的多功能I型蛋白来完成的<ref>{{cite journal | vauthors = Chirala SS, Wakil SJ | title = Structure and function of animal fatty acid synthase | journal = Lipids | volume = 39 | issue = 11 | pages = 1045–53 | date = November 2004 | pmid = 15726818 | doi = 10.1007/s11745-004-1329-9 | s2cid = 4043407 }}</ref>，而在植物的质体和细菌中，则由单独的II型酶来完成每一步<ref>{{cite journal | vauthors = White SW, Zheng J, Zhang YM | title = The structural biology of type II fatty acid biosynthesis | journal = Annual Review of Biochemistry | volume = 74 | issue = | pages = 791–831 | year = 2005 | pmid = 15952903 | doi = 10.1146/annurev.biochem.74.082803.133524 }}</ref><ref>{{cite journal | vauthors = Ohlrogge JB, Jaworski JG | title = Regulation of Fatty Acid Synthesis | journal = Annual Review of Plant Physiology and Plant Molecular Biology | volume = 48 | issue = | pages = 109–136 | date = June 1997 | pmid = 15012259 | doi = 10.1146/annurev.arplant.48.1.109 | s2cid = 46348092 }}</ref>。

[[Terpene]]s and [[terpenoid|isoprenoids]] are a large class of lipids that include the [[carotenoid]]s and form the largest class of plant [[natural product]]s. These compounds are made by the assembly and modification of [[isoprene]] units donated from the reactive precursors [[isopentenyl pyrophosphate]] and [[dimethylallyl pyrophosphate]]. These precursors can be made in different ways. In animals and archaea, the [[mevalonate pathway]] produces these compounds from acetyl-CoA, while in plants and bacteria the [[non-mevalonate pathway]] uses pyruvate and [[glyceraldehyde 3-phosphate]] as substrates. One important reaction that uses these activated isoprene donors is [[steroid biosynthesis|sterol biosynthesis]]. Here, the isoprene units are joined together to make [[squalene]] and then folded up and formed into a set of rings to make [[lanosterol]]. Lanosterol can then be converted into other sterol such as [[cholesterol]] and [[ergosterol]].

Terpenes and isoprenoids are a large class of lipids that include the carotenoids and form the largest class of plant natural products. These compounds are made by the assembly and modification of isoprene units donated from the reactive precursors isopentenyl pyrophosphate and dimethylallyl pyrophosphate. These precursors can be made in different ways. In animals and archaea, the mevalonate pathway produces these compounds from acetyl-CoA, while in plants and bacteria the non-mevalonate pathway uses pyruvate and glyceraldehyde 3-phosphate as substrates. One important reaction that uses these activated isoprene donors is sterol biosynthesis. Here, the isoprene units are joined together to make squalene and then folded up and formed into a set of rings to make lanosterol. Lanosterol can then be converted into other sterol such as cholesterol and ergosterol.

萜烯和异戊二烯是一大类脂类，包括类胡萝卜素，也是最大的一类植物天然产品<ref>{{cite journal | vauthors = Dubey VS, Bhalla R, Luthra R | title = An overview of the non-mevalonate pathway for terpenoid biosynthesis in plants | journal = Journal of Biosciences | volume = 28 | issue = 5 | pages = 637–46 | date = September 2003 | pmid = 14517367 | doi = 10.1007/BF02703339 | url = http://www.ias.ac.in/jbiosci/sep2003/637.pdf | url-status = dead | s2cid = 27523830 | archive-url = https://web.archive.org/web/20070415213325/http://www.ias.ac.in/jbiosci/sep2003/637.pdf | df = | archive-date = 15 April 2007 }}</ref>。这些化合物是由反应性前体焦磷酸异戊烯酯和焦磷酸二甲基烯丙基酯所提供的异戊二烯单元组装和改性而成。这些前体可以靠不同的途径制造<ref name=Kuzuyama>{{cite journal | vauthors = Kuzuyama T, Seto H | title = Diversity of the biosynthesis of the isoprene units | journal = Natural Product Reports | volume = 20 | issue = 2 | pages = 171–83 | date = April 2003 | pmid = 12735695 | doi = 10.1039/b109860h }}</ref>。在动物和古生物中，甲戊二酸途径从乙酰辅酶A产生这些化合物<ref>{{cite journal | vauthors = Grochowski LL, Xu H, White RH | title = Methanocaldococcus jannaschii uses a modified mevalonate pathway for biosynthesis of isopentenyl diphosphate | journal = Journal of Bacteriology | volume = 188 | issue = 9 | pages = 3192–8 | date = May 2006 | pmid = 16621811 | pmc = 1447442 | doi = 10.1128/JB.188.9.3192-3198.2006 }}</ref>，而在植物和细菌中，非甲戊二酸途径使用丙酮酸和甘油醛3-磷酸作为底物。使用这些活化的异戊二烯供体的一个重要反应是固醇的生物合成<ref name=Kuzuyama/><ref>{{cite journal | vauthors = Lichtenthaler HK | title = The 1-Deoxy-D-Xylulose-5-Phosphate Pathway of Isoprenoid Biosynthesis in Plants | journal = Annual Review of Plant Physiology and Plant Molecular Biology | volume = 50 | issue = | pages = 47–65 | date = June 1999 | pmid = 15012203 | doi = 10.1146/annurev.arplant.50.1.47 }}</ref>。在该反应中，异戊二烯单元连接在一起，制成角鲨烯，然后折叠起来形成一组环，制成羊毛固醇<ref name=Schroepfer>{{cite journal | vauthors = Schroepfer GJ | title = Sterol biosynthesis | journal = Annual Review of Biochemistry | volume = 50 | issue = | pages = 585–621 | year = 1981 | pmid = 7023367 | doi = 10.1146/annurev.bi.50.070181.003101 }}</ref>。羊毛固醇随后可转化为其他固醇，如胆固醇和麦角固醇<ref name=Schroepfer/><ref>{{cite journal | vauthors = Lees ND, Skaggs B, Kirsch DR, Bard M | title = Cloning of the late genes in the ergosterol biosynthetic pathway of Saccharomyces cerevisiae--a review | journal = Lipids | volume = 30 | issue = 3 | pages = 221–6 | date = March 1995 | pmid = 7791529 | doi = 10.1007/BF02537824 | s2cid = 4019443 }}</ref>。

===Proteins===
蛋白质类
{{further|Protein biosynthesis|Amino acid synthesis}}

更多信息：蛋白质生物合成和氨基酸合成

Organisms vary in their ability to synthesize the 20 common amino acids. Most bacteria and plants can synthesize all twenty, but mammals can only synthesize eleven nonessential amino acids, so nine [[essential amino acid]]s must be obtained from food. Some simple [[parasite]]s, such as the bacteria ''[[Mycoplasma pneumoniae]]'', lack all amino acid synthesis and take their amino acids directly from their hosts. All amino acids are synthesized from intermediates in glycolysis, the citric acid cycle, or the pentose phosphate pathway. Nitrogen is provided by [[glutamate]] and [[glutamine]]. Nonessensial amino acid synthesis depends on the formation of the appropriate alpha-keto acid, which is then [[Transaminase|transaminated]] to form an amino acid.

Organisms vary in their ability to synthesize the 20 common amino acids. Most bacteria and plants can synthesize all twenty, but mammals can only synthesize eleven nonessential amino acids, so nine essential amino acids must be obtained from food. All amino acids are synthesized from intermediates in glycolysis, the citric acid cycle, or the pentose phosphate pathway. Nitrogen is provided by glutamate and glutamine. Nonessensial amino acid synthesis depends on the formation of the appropriate alpha-keto acid, which is then transaminated to form an amino acid.

生物体合成这20种常见氨基酸的能力各不相同。大多数细菌和植物都能合成这20种氨基酸，但哺乳动物只能合成11种非必需氨基酸，因此必须从食物中获得9种必需氨基酸<ref name=Nelson/>。所有的氨基酸都是由糖酵解、三羧酸循环或磷酸戊糖途径的中间产物合成的<ref>{{cite journal | vauthors = Himmelreich R, Hilbert H, Plagens H, Pirkl E, Li BC, Herrmann R | title = Complete sequence analysis of the genome of the bacterium Mycoplasma pneumoniae | journal = Nucleic Acids Research | volume = 24 | issue = 22 | pages = 4420–49 | date = November 1996 | pmid = 8948633 | pmc = 146264 | doi = 10.1093/nar/24.22.4420 }}</ref>。氮由谷氨酸和谷氨酰胺提供。非关键氨基酸的合成取决于适当的α-酮酸的形成，它可以转氨基形成氨基酸<ref>{{cite book |last1 = Guyton |first1 = Arthur C. | first2 = John E. | last2 = Hall | name-list-style = vanc |title=Textbook of Medical Physiology |url=https://archive.org/details/textbookmedicalp00acgu |url-access=limited |publisher=Elsevier |year=2006 |location=Philadelphia |pages=[https://archive.org/details/textbookmedicalp00acgu/page/n889 855]–6 |isbn=978-0-7216-0240-0}}</ref>。

Amino acids are made into proteins by being joined together in a chain of [[peptide bond]]s. Each different protein has a unique sequence of amino acid residues: this is its [[primary structure]]. Just as the letters of the alphabet can be combined to form an almost endless variety of words, amino acids can be linked in varying sequences to form a huge variety of proteins. Proteins are made from amino acids that have been activated by attachment to a [[transfer RNA]] molecule through an [[ester]] bond. This [[aminoacyl-tRNA]] precursor is produced in an [[Adenosine triphosphate|ATP]]-dependent reaction carried out by an [[aminoacyl tRNA synthetase]] This aminoacyl-tRNA is then a substrate for the [[ribosome]], which joins the amino acid onto the elongating protein chain, using the sequence information in a [[messenger RNA]].

Amino acids are made into proteins by being joined together in a chain of peptide bonds. Each different protein has a unique sequence of amino acid residues: this is its primary structure. Just as the letters of the alphabet can be combined to form an almost endless variety of words, amino acids can be linked in varying sequences to form a huge variety of proteins. Proteins are made from amino acids that have been activated by attachment to a transfer RNA molecule through an ester bond. This aminoacyl-tRNA precursor is produced in an ATP-dependent reaction carried out by an aminoacyl tRNA synthetase. This aminoacyl-tRNA is then a substrate for the ribosome, which joins the amino acid onto the elongating protein chain, using the sequence information in a messenger RNA.

氨基酸通过肽键链连接成蛋白质。每种不同的蛋白质都有一个独特的氨基酸残基序列：这就是它的主要结构。就像字母表的字母可以组合成无穷无尽的各种单词一样，氨基酸也能以不同的序列连接起来，形成种类繁多的蛋白质。蛋白质是由氨基酸制成的，这些氨基酸通过酯键附着在转运RNA(tRNA)分子上而被激活。氨基酰tRNA前体是在靠氨基酰tRNA合成酶进行的ATP依赖性反应中产生的.<ref>{{cite journal | vauthors = Ibba M, Söll D | title = The renaissance of aminoacyl-tRNA synthesis | journal = EMBO Reports | volume = 2 | issue = 5 | pages = 382–7 | date = May 2001 | pmid = 11375928 | pmc = 1083889 | doi = 10.1093/embo-reports/kve095 | url = http://www.molcells.org/home/journal/include/downloadPdf.asp?articleuid={A158E3B4-2423-4806-9A30-4B93CDA76DA0} | url-status = dead | archive-url = https://web.archive.org/web/20110501181419/http://www.molcells.org/home/journal/include/downloadPdf.asp?articleuid=%7BA158E3B4-2423-4806-9A30-4B93CDA76DA0%7D | df = | archive-date = 1 May 2011 }}</ref>。然后，这种氨基酰tRNA成为核糖体的底物，核糖体利用信使RNA中的序列信息将氨基酸连接到伸长的蛋白质链上<ref>{{cite journal | vauthors = Lengyel P, Söll D | title = Mechanism of protein biosynthesis | journal = Bacteriological Reviews | volume = 33 | issue = 2 | pages = 264–301 | date = June 1969 | pmid = 4896351 | pmc = 378322 | doi = 10.1128/MMBR.33.2.264-301.1969 }}</ref>。

===Nucleotide synthesis and salvage===
核苷酸的合成和补救途径
{{further|Nucleotide salvage|Pyrimidine biosynthesis|Purine#Metabolism}}

更多信息：核苷酸补救途径，嘧啶的生物合成和嘌呤§代谢

Nucleotides are made from amino acids, carbon dioxide and [[formic acid]] in pathways that require large amounts of metabolic energy. Consequently, most organisms have efficient systems to salvage preformed nucleotides. [[Purine]]s are synthesized as [[nucleoside]]s (bases attached to [[ribose]]). Both [[adenine]] and [[guanine]] are made from the precursor nucleoside [[inosine]] monophosphate, which is synthesized using atoms from the amino acids [[glycine]], [[glutamine]], and [[aspartic acid]], as well as [[formate]] transferred from the [[coenzyme]] [[folic acid|tetrahydrofolate]]. [[Pyrimidine]]s, on the other hand, are synthesized from the base [[Pyrimidinecarboxylic acid|orotate]], which is formed from glutamine and aspartate.

Nucleotides are made from amino acids, carbon dioxide and formic acid in pathways that require large amounts of metabolic energy. Consequently, most organisms have efficient systems to salvage preformed nucleotides. Purines are synthesized as nucleosides (bases attached to ribose). Both adenine and guanine are made from the precursor nucleoside inosine monophosphate, which is synthesized using atoms from the amino acids glycine, glutamine, and aspartic acid, as well as formate transferred from the coenzyme tetrahydrofolate. Pyrimidines, on the other hand, are synthesized from the base orotate, which is formed from glutamine and aspartate.

核苷酸由氨基酸、二氧化碳和甲酸在需要大量代谢能量的途径中生成<ref name=Rudolph>{{cite journal | vauthors = Rudolph FB | title = The biochemistry and physiology of nucleotides | journal = The Journal of Nutrition | volume = 124 | issue = 1 Suppl | pages = 124S–127S | date = January 1994 | pmid = 8283301 | doi = 10.1093/jn/124.suppl_1.124S }} {{cite journal | vauthors = Zrenner R, Stitt M, Sonnewald U, Boldt R | title = Pyrimidine and purine biosynthesis and degradation in plants | journal = Annual Review of Plant Biology | volume = 57 | issue = | pages = 805–36 | year = 2006 | pmid = 16669783 | doi = 10.1146/annurev.arplant.57.032905.105421 }}</ref>。因此，大多数生物体都有有效的系统来挽救预先形成的核苷酸<ref name=Rudolph/><ref>{{cite journal | vauthors = Stasolla C, Katahira R, Thorpe TA, Ashihara H | title = Purine and pyrimidine nucleotide metabolism in higher plants | journal = Journal of Plant Physiology | volume = 160 | issue = 11 | pages = 1271–95 | date = November 2003 | pmid = 14658380 | doi = 10.1078/0176-1617-01169 }}</ref>。嘌呤以核苷的形式合成(碱基附着在核糖上)。腺嘌呤和鸟嘌呤都是由一磷酸核苷肌苷前体合成的<ref name="pmid 22531138">{{cite journal | vauthors = Davies O, Mendes P, Smallbone K, Malys N | title = Characterisation of multiple substrate-specific (d)ITP/(d)XTPase and modelling of deaminated purine nucleotide metabolism | journal = BMB Reports | volume = 45 | issue = 4 | pages = 259–64 | date = April 2012 | pmid = 22531138 | doi = 10.5483/BMBRep.2012.45.4.259 | url = http://wrap.warwick.ac.uk/49510/1/WRAP_Malys_%5B45-4%5D1204261917_%28259-264%29BMB_11-169.pdf }}</ref>，而前体是由甘氨酸、谷氨酰胺和天冬氨酸的原子合成的，从辅酶四氢叶酸转移来的甲酸酯也是如此。另一方面，嘧啶是由磷酸基合成的，而磷酸基是由谷氨酰胺和天门冬氨酸形成的<ref>{{cite journal | vauthors = Smith JL | title = Enzymes of nucleotide synthesis | journal = Current Opinion in Structural Biology | volume = 5 | issue = 6 | pages = 752–7 | date = December 1995 | pmid = 8749362 | doi = 10.1016/0959-440X(95)80007-7 }}</ref>。

==Xenobiotics and redox metabolism==
异种生物学和氧化还原代谢
{{further|Xenobiotic metabolism|Drug metabolism|Alcohol metabolism|Antioxidant}}

更多信息：异生物质代谢，药物代谢，酒精代谢和抗氧化剂

All organisms are constantly exposed to compounds that they cannot use as foods and would be harmful if they accumulated in cells, as they have no metabolic function. These potentially damaging compounds are called [[xenobiotic]]s. Xenobiotics such as [[drug|synthetic drugs]], [[poison|natural poisons]] and [[antibiotic]]s are detoxified by a set of xenobiotic-metabolizing enzymes. In humans, these include [[cytochrome P450|cytochrome P450 oxidases]], [[Glucuronosyltransferase|UDP-glucuronosyltransferases]], and [[glutathione S-transferase|glutathione ''S''-transferases]]. This system of enzymes acts in three stages to firstly oxidize the xenobiotic (phase I) and then conjugate water-soluble groups onto the molecule (phase II). The modified water-soluble xenobiotic can then be pumped out of cells and in multicellular organisms may be further metabolized before being excreted (phase III). In [[ecology]], these reactions are particularly important in microbial [[biodegradation]] of pollutants and the [[bioremediation]] of contaminated land and oil spills. Many of these microbial reactions are shared with multicellular organisms, but due to the incredible diversity of types of microbes these organisms are able to deal with a far wider range of xenobiotics than multicellular organisms, and can degrade even [[persistent organic pollutant]]s such as [[organochloride]] compounds.
All organisms are constantly exposed to compounds that they cannot use as foods and would be harmful if they accumulated in cells, as they have no metabolic function. These potentially damaging compounds are called xenobiotics. Xenobiotics such as synthetic drugs, natural poisons and antibiotics are detoxified by a set of xenobiotic-metabolizing enzymes. In humans, these include cytochrome P450 oxidases, UDP-glucuronosyltransferases, and glutathione S-transferases. This system of enzymes acts in three stages to firstly oxidize the xenobiotic (phase I) and then conjugate water-soluble groups onto the molecule (phase II). The modified water-soluble xenobiotic can then be pumped out of cells and in multicellular organisms may be further metabolized before being excreted (phase III). In ecology, these reactions are particularly important in microbial biodegradation of pollutants and the bioremediation of contaminated land and oil spills. Many of these microbial reactions are shared with multicellular organisms, but due to the incredible diversity of types of microbes these organisms are able to deal with a far wider range of xenobiotics than multicellular organisms, and can degrade even persistent organic pollutants such as organochloride compounds.

所有的生物都不断地接触到它们不能进食的化合物，如果它们在细胞中积累这些化合物就会被伤害，因为它们没有新陈代谢功能。这些具有潜在破坏性的化合物被称为异生物质<ref>{{cite journal | vauthors = Testa B, Krämer SD | title = The biochemistry of drug metabolism--an introduction: part 1. Principles and overview | journal = Chemistry & Biodiversity | volume = 3 | issue = 10 | pages = 1053–101 | date = October 2006 | pmid = 17193224 | doi = 10.1002/cbdv.200690111 | s2cid = 28872968 }}</ref>。合成药物、天然毒物和抗生素等异生物质是通过一系列异生物质代谢酶来解毒的。在人体中，这些酶包括细胞色素 P450氧化酶<ref>{{cite journal | vauthors = Danielson PB | title = The cytochrome P450 superfamily: biochemistry, evolution and drug metabolism in humans | journal = Current Drug Metabolism | volume = 3 | issue = 6 | pages = 561–97 | date = December 2002 | pmid = 12369887 | doi = 10.2174/1389200023337054 }}</ref>、UDP-葡萄糖醛酸转移酶<ref>{{cite journal | vauthors = King CD, Rios GR, Green MD, Tephly TR | title = UDP-glucuronosyltransferases | journal = Current Drug Metabolism | volume = 1 | issue = 2 | pages = 143–61 | date = September 2000 | pmid = 11465080 | doi = 10.2174/1389200003339171 }}</ref>和谷胱甘肽 s- 转移酶。这套酶系统的作用分为三个阶段<ref>{{cite journal | vauthors = Sheehan D, Meade G, Foley VM, Dowd CA | title = Structure, function and evolution of glutathione transferases: implications for classification of non-mammalian members of an ancient enzyme superfamily | journal = The Biochemical Journal | volume = 360 | issue = Pt 1 | pages = 1–16 | date = November 2001 | pmid = 11695986 | pmc = 1222196 | doi = 10.1042/0264-6021:3600001 }}</ref>，首先氧化异生物质(第一阶段) ，然后将水溶性基团共轭到分子上(第二阶段)。经过降解的水溶性异生物质随后会从细胞中泵出，对多细胞生物来说，还会在排出之前进一步代谢(第三阶段)。在生态学中，这些反应在微生物对污染物的生物降解以及污染土地和溢油的生物修复中尤为重要<ref>{{cite journal | vauthors = Galvão TC, Mohn WW, de Lorenzo V | title = Exploring the microbial biodegradation and biotransformation gene pool | journal = Trends in Biotechnology | volume = 23 | issue = 10 | pages = 497–506 | date = October 2005 | pmid = 16125262 | doi = 10.1016/j.tibtech.2005.08.002 }}</ref>。这些微生物反应中有许多是与多细胞生物相同的，但是由于微生物种类的惊人多样性，这些微生物能够处理比多细胞生物更广泛的异生物质，甚至能够降解有机氯化合物等持久性有机污染物<ref>{{cite journal | vauthors = Janssen DB, Dinkla IJ, Poelarends GJ, Terpstra P | title = Bacterial degradation of xenobiotic compounds: evolution and distribution of novel enzyme activities | journal = Environmental Microbiology | volume = 7 | issue = 12 | pages = 1868–82 | date = December 2005 | pmid = 16309386 | doi = 10.1111/j.1462-2920.2005.00966.x | url = https://pure.rug.nl/ws/files/3623678/2005EnvironMicrobiolJanssen.pdf }}</ref>
。

A related problem for [[aerobic organism]]s is [[oxidative stress]]. Here, processes including [[oxidative phosphorylation]] and the formation of [[disulfide bond]]s during [[protein folding]] produce [[reactive oxygen species]] such as [[hydrogen peroxide]]. These damaging oxidants are removed by [[antioxidant]] metabolites such as [[glutathione]] and enzymes such as [[catalase]]s and [[peroxidase]]s.

A related problem for aerobic organisms is oxidative stress. Here, processes including oxidative phosphorylation and the formation of disulfide bonds during protein folding produce reactive oxygen species such as hydrogen peroxide. These damaging oxidants are removed by antioxidant metabolites such as glutathione and enzymes such as catalases and peroxidases.

对于好氧生物来说，一个相关的问题是氧化应激<ref name=Davies>{{cite journal | vauthors = Davies KJ | title = Oxidative stress: the paradox of aerobic life | journal = Biochemical Society Symposium | volume = 61 | issue = | pages = 1–31 | year = 1995 | pmid = 8660387 | doi = 10.1042/bss0610001 }}</ref>。这个过程包括氧化磷酸化和蛋白质折叠时二硫键的形成，它产生了活性氧类（如过氧化氢）<ref>{{cite journal | vauthors = Tu BP, Weissman JS | title = Oxidative protein folding in eukaryotes: mechanisms and consequences | journal = The Journal of Cell Biology | volume = 164 | issue = 3 | pages = 341–6 | date = February 2004 | pmid = 14757749 | pmc = 2172237 | doi = 10.1083/jcb.200311055 }}</ref>。这些破坏性的氧化剂被抗氧化代谢物（如谷胱甘肽和酶）和酶（如过氧化氢酶和过氧化物酶）去除<ref name=Sies>{{cite journal | vauthors = Sies H | title = Oxidative stress: oxidants and antioxidants | journal = Experimental Physiology | volume = 82 | issue = 2 | pages = 291–5 | date = March 1997 | pmid = 9129943 | doi = 10.1113/expphysiol.1997.sp004024 | s2cid = 20240552 | url = http://ep.physoc.org/cgi/reprint/82/2/291.pdf | access-date = 9 March 2007 | url-status = dead | archive-url = https://web.archive.org/web/20090325001126/http://ep.physoc.org/cgi/reprint/82/2/291.pdf | archive-date = 25 March 2009 }}</ref><ref name=Vertuani>{{cite journal | vauthors = Vertuani S, Angusti A, Manfredini S | title = The antioxidants and pro-antioxidants network: an overview | journal = Current Pharmaceutical Design | volume = 10 | issue = 14 | pages = 1677–94 | year = 2004 | pmid = 15134565 | doi = 10.2174/1381612043384655 | s2cid = 43713549 }}</ref>。

==Thermodynamics of living organisms==
生命有机体的热力学
{{further|Biological thermodynamics}}

更多信息：生物热力学

Living organisms must obey the [[laws of thermodynamics]], which describe the transfer of heat and [[work (thermodynamics)|work]]. The [[second law of thermodynamics]] states that in any [[closed system]], the amount of [[entropy]] (disorder) cannot decrease. Although living organisms' amazing complexity appears to contradict this law, life is possible as all organisms are [[open system (systems theory)|open systems]] that exchange matter and energy with their surroundings. Thus living systems are not in [[Thermodynamic equilibrium|equilibrium]], but instead are [[dissipative system]]s that maintain their state of high complexity by causing a larger increase in the entropy of their environments. The metabolism of a cell achieves this by coupling the [[spontaneous process]]es of catabolism to the non-spontaneous processes of anabolism. In [[non-equilibrium thermodynamics|thermodynamic]] terms, metabolism maintains order by creating disorder.

Living organisms must obey the laws of thermodynamics, which describe the transfer of heat and work. The second law of thermodynamics states that in any closed system, the amount of entropy (disorder) cannot decrease. Although living organisms' amazing complexity appears to contradict this law, life is possible as all organisms are open systems that exchange matter and energy with their surroundings. Thus living systems are not in equilibrium, but instead are dissipative systems that maintain their state of high complexity by causing a larger increase in the entropy of their environments. The metabolism of a cell achieves this by coupling the spontaneous processes of catabolism to the non-spontaneous processes of anabolism. In thermodynamic terms, metabolism maintains order by creating disorder.

生命有机体一定会遵守热力学定律，该定律描述了热量和功的传递。热力学第二定律指出，在任何封闭系统中，熵的总量（混乱度）不会减少。尽管生物体惊人的复杂性似乎与这一定律相矛盾，但生命是可能的，因为它们是与环境交换物质和能量的开放系统。也就是说，生命系统并不处于平衡状态，而是耗散系统，它通过大量增加环境熵来维持其高度复杂的状态<ref>{{cite journal | vauthors = von Stockar U, Liu J | title = Does microbial life always feed on negative entropy? Thermodynamic analysis of microbial growth | journal = Biochimica et Biophysica Acta (BBA) - Bioenergetics | volume = 1412 | issue = 3 | pages = 191–211 | date = August 1999 | pmid = 10482783 | doi = 10.1016/S0005-2728(99)00065-1 }}</ref>。细胞的新陈代谢通过将分解代谢的自发过程和合成代谢的非自发过程进行耦合来实现这一点。从热力学的角度来看，新陈代谢通过制造混乱来维持秩序<ref>{{cite journal | vauthors = Demirel Y, Sandler SI | title = Thermodynamics and bioenergetics | journal = Biophysical Chemistry | volume = 97 | issue = 2–3 | pages = 87–111 | date = June 2002 | pmid = 12050002 | doi = 10.1016/S0301-4622(02)00069-8 | url = https://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=1006&context=chemengthermalmech }}</ref>。

==Regulation and control==
调控
{{further|Metabolic pathway|Metabolic control analysis|Hormone|Regulatory enzymes|Cell signaling}}

更多信息：代谢途径，代谢控制分析，激素，调节酶和细胞信号转导

As the environments of most organisms are constantly changing, the reactions of metabolism must be finely [[Control theory|regulated]] to maintain a constant set of conditions within cells, a condition called [[homeostasis]]. Metabolic regulation also allows organisms to respond to signals and interact actively with their environments. Two closely linked concepts are important for understanding how metabolic pathways are controlled. Firstly, the ''regulation'' of an enzyme in a pathway is how its activity is increased and decreased in response to signals. Secondly, the ''control'' exerted by this enzyme is the effect that these changes in its activity have on the overall rate of the pathway (the [[flux]] through the pathway). For example, an enzyme may show large changes in activity (''i.e.'' it is highly regulated) but if these changes have little effect on the flux of a metabolic pathway, then this enzyme is not involved in the control of the pathway.

As the environments of most organisms are constantly changing, the reactions of metabolism must be finely regulated to maintain a constant set of conditions within cells, a condition called homeostasis. Metabolic regulation also allows organisms to respond to signals and interact actively with their environments. Two closely linked concepts are important for understanding how metabolic pathways are controlled. Firstly, the regulation of an enzyme in a pathway is how its activity is increased and decreased in response to signals. Secondly, the control exerted by this enzyme is the effect that these changes in its activity have on the overall rate of the pathway (the flux through the pathway). For example, an enzyme may show large changes in activity (i.e. it is highly regulated) but if these changes have little effect on the flux of a metabolic pathway, then this enzyme is not involved in the control of the pathway.

由于大多数生物体的环境是不断变化的，因此它们必须对新陈代谢的反应进行精细的调节，以维持细胞内一系列恒定的条件，这种条件称为稳态<ref>{{cite journal | vauthors = Albert R | title = Scale-free networks in cell biology | journal = Journal of Cell Science | volume = 118 | issue = Pt 21 | pages = 4947–57 | date = November 2005 | pmid = 16254242 | doi = 10.1242/jcs.02714 | arxiv = q-bio/0510054 | s2cid = 3001195 | bibcode = 2005q.bio....10054A }}</ref><ref>{{cite journal | vauthors = Brand MD | title = Regulation analysis of energy metabolism | journal = The Journal of Experimental Biology | volume = 200 | issue = Pt 2 | pages = 193–202 | date = January 1997 | pmid = 9050227 | url = http://jeb.biologists.org/cgi/reprint/200/2/193 }}</ref>。代谢调节也使生物体能够对信号作出反应，并与环境积极互动。有两个密切相关的概念对于理解“代谢途径是如何被控制的”十分重要<ref>{{cite journal | vauthors = Soyer OS, Salathé M, Bonhoeffer S | title = Signal transduction networks: topology, response and biochemical processes | journal = Journal of Theoretical Biology | volume = 238 | issue = 2 | pages = 416–25 | date = January 2006 | pmid = 16045939 | doi = 10.1016/j.jtbi.2005.05.030 }}</ref>。首先，途径中酶的调节是指其活性如何响应信号从而增加和减少。其次，这种酶所施加的控制是指它的活性变化对通路的总体速率（通过通路的通量）的影响<ref name=Salter>{{cite journal | vauthors = Salter M, Knowles RG, Pogson CI | title = Metabolic control | journal = Essays in Biochemistry | volume = 28 | issue = | pages = 1–12 | year = 1994 | pmid = 7925313 }}</ref>。例如，一种酶可能表现出很大的活性变化(即它是高度受控的)，但如果这些变化对某一代谢途径的通量影响不大，那么这种酶就不参与该途径的控制<ref>{{cite journal | vauthors = Westerhoff HV, Groen AK, Wanders RJ | title = Modern theories of metabolic control and their applications (review) | journal = Bioscience Reports | volume = 4 | issue = 1 | pages = 1–22 | date = January 1984 | pmid = 6365197 | doi = 10.1007/BF01120819 | s2cid = 27791605 }}</ref>。

[[File:Insulin glucose metabolism ZP.svg|thumb|right|upright=1.35|胰岛素对葡萄糖摄取和代谢的影响。胰岛素与其受体（1）结合，继而启动许多蛋白质激活级联反应（2）。其中包括：Glut-4转运蛋白向[[质膜]]的转运和葡萄糖的流入（3），[[糖原]]合成（4），[[糖酵解]]（5）和[[脂肪酸]]合成（6）。]]

There are multiple levels of metabolic regulation. In intrinsic regulation, the metabolic pathway self-regulates to respond to changes in the levels of substrates or products; for example, a decrease in the amount of product can increase the [[flux]] through the pathway to compensate. This type of regulation often involves [[allosteric regulation]] of the activities of multiple enzymes in the pathway. Extrinsic control involves a cell in a multicellular organism changing its metabolism in response to signals from other cells. These signals are usually in the form of water soluble messengers such as [[hormone]]s and [[growth factor]]s and are detected by specific [[receptor (biochemistry)|receptors]] on the cell surface. These signals are then transmitted inside the cell by [[second messenger system]]s that often involved the [[phosphorylation]] of proteins.

There are multiple levels of metabolic regulation. In intrinsic regulation, the metabolic pathway self-regulates to respond to changes in the levels of substrates or products; for example, a decrease in the amount of product can increase the flux through the pathway to compensate. Extrinsic control involves a cell in a multicellular organism changing its metabolism in response to signals from other cells. These signals are usually in the form of water soluble messengers such as hormones and growth factors and are detected by specific receptors on the cell surface. These signals are then transmitted inside the cell by second messenger systems that often involved the phosphorylation of proteins.

新陈代谢调节有多个层次。在内在调节中，代谢途径自我调节，以应对底物或产物数量的变化；例如，产物数量的减少可以增加通过该途径的通量以进行补偿<ref name=Salter/>。外在控制是指多细胞生物体中的一个细胞根据来自其他细胞的信号改变其代谢<ref>{{cite journal | vauthors = Fell DA, Thomas S | title = Physiological control of metabolic flux: the requirement for multisite modulation | journal = The Biochemical Journal | volume = 311 ( Pt 1) | issue = Pt 1 | pages = 35–9 | date = October 1995 | pmid = 7575476 | pmc = 1136115 | doi = 10.1042/bj3110035 }}</ref>。这些信号通常以水溶性信使的形式出现（如激素和生长因子）<ref>{{cite journal | vauthors = Hendrickson WA | title = Transduction of biochemical signals across cell membranes | journal = Quarterly Reviews of Biophysics | volume = 38 | issue = 4 | pages = 321–30 | date = November 2005 | pmid = 16600054 | doi = 10.1017/S0033583506004136 }}</ref>，并被细胞表面的特定受体检测到。然后，这些信号通过第二信使系统在细胞内传递，该系统通常涉及蛋白质的磷酸化<ref>{{cite journal | vauthors = Cohen P | title = The regulation of protein function by multisite phosphorylation--a 25 year update | journal = Trends in Biochemical Sciences | volume = 25 | issue = 12 | pages = 596–601 | date = December 2000 | pmid = 11116185 | doi = 10.1016/S0968-0004(00)01712-6 }}</ref>。

A very well understood example of extrinsic control is the regulation of glucose metabolism by the hormone [[insulin]]. Insulin is produced in response to rises in [[blood sugar|blood glucose levels]]. Binding of the hormone to [[insulin receptor]]s on cells then activates a cascade of [[protein kinase]]s that cause the cells to take up glucose and convert it into storage molecules such as fatty acids and [[glycogen]]. The metabolism of glycogen is controlled by activity of [[phosphorylase]], the enzyme that breaks down glycogen, and [[glycogen synthase]], the enzyme that makes it. These enzymes are regulated in a reciprocal fashion, with phosphorylation inhibiting glycogen synthase, but activating phosphorylase. Insulin causes glycogen synthesis by activating [[phosphatase|protein phosphatases]] and producing a decrease in the phosphorylation of these enzymes.

A very well understood example of extrinsic control is the regulation of glucose metabolism by the hormone insulin. Insulin is produced in response to rises in blood glucose levels. Binding of the hormone to insulin receptors on cells then activates a cascade of protein kinases that cause the cells to take up glucose and convert it into storage molecules such as fatty acids and glycogen. The metabolism of glycogen is controlled by activity of phosphorylase, the enzyme that breaks down glycogen, and glycogen synthase, the enzyme that makes it. These enzymes are regulated in a reciprocal fashion, with phosphorylation inhibiting glycogen synthase, but activating phosphorylase. Insulin causes glycogen synthesis by activating protein phosphatases and producing a decrease in the phosphorylation of these enzymes.

一个非常好理解的外在控制的例子是激素胰岛素对葡萄糖代谢的调节<ref>{{cite journal | vauthors = Lienhard GE, Slot JW, James DE, Mueckler MM | title = How cells absorb glucose | journal = Scientific American | volume = 266 | issue = 1 | pages = 86–91 | date = January 1992 | pmid = 1734513 | doi = 10.1038/scientificamerican0192-86 | bibcode = 1992SciAm.266a..86L }}</ref>。胰岛素是在血糖升高时产生的。胰岛素与细胞上的胰岛素受体结合，然后激活一连串的蛋白激酶，使细胞吸收葡萄糖，并将其转化为储存分子（如脂肪酸和糖原）<ref>{{cite journal | vauthors = Roach PJ | title = Glycogen and its metabolism | journal = Current Molecular Medicine | volume = 2 | issue = 2 | pages = 101–20 | date = March 2002 | pmid = 11949930 | doi = 10.2174/1566524024605761 }}</ref>。糖原的新陈代谢受到分解糖原的磷酸化酶和制造糖原的糖原合成酶的活性控制。这些酶的调节方式是相互的，磷酸化作用抑制糖原合成酶，但激活磷酸化酶。胰岛素通过激活蛋白磷酸酶使这些酶的磷酸化程度降低，从而触发糖原合成<ref>{{cite journal | vauthors = Newgard CB, Brady MJ, O'Doherty RM, Saltiel AR | title = Organizing glucose disposal: emerging roles of the glycogen targeting subunits of protein phosphatase-1 | journal = Diabetes | volume = 49 | issue = 12 | pages = 1967–77 | date = December 2000 | pmid = 11117996 | doi = 10.2337/diabetes.49.12.1967 | url = http://diabetes.diabetesjournals.org/cgi/reprint/49/12/1967.pdf }}</ref>。

==Evolution==
演化
{{further|Molecular evolution|Phylogenetics}}

更多信息：分子进化与系统发育

[[File:Tree of life int.svg|thumb|right|upright=1.8|[[演化树显示了来自全部三个生命领域的生物体的共同祖先。[[细菌]]呈蓝色，[[真核生物]]呈红色，[[古菌]]呈绿色。树木周围显示了一些门的相对位置。]]

Evolutionary tree showing the common ancestry of organisms from all three domains of life. Bacteria are colored blue, eukaryotes red, and archaea green. Relative positions of some of the phyla included are shown around the tree.]]

The central pathways of metabolism described above, such as glycolysis and the citric acid cycle, are present in all [[Three-domain system|three domains]] of living things and were present in the [[last universal common ancestor]]. This universal ancestral cell was [[prokaryote|prokaryotic]] and probably a [[methanogen]] that had extensive amino acid, nucleotide, carbohydrate and lipid metabolism. The retention of these ancient pathways during later [[evolution]] may be the result of these reactions having been an optimal solution to their particular metabolic problems, with pathways such as glycolysis and the citric acid cycle producing their end products highly efficiently and in a minimal number of steps. The first pathways of enzyme-based metabolism may have been parts of [[purine]] nucleotide metabolism, while previous metabolic pathways were a part of the ancient [[RNA world hypothesis|RNA world]].

The central pathways of metabolism described above, such as glycolysis and the citric acid cycle, are present in all three domains of living things and were present in the last universal common ancestor.This universal ancestral cell was prokaryotic and probably a methanogen that had extensive amino acid, nucleotide, carbohydrate and lipid metabolism.The retention of these ancient pathways during later evolution may be the result of these reactions having been an optimal solution to their particular metabolic problems, with pathways such as glycolysis and the citric acid cycle producing their end products highly efficiently and in a minimal number of steps.The first pathways of enzyme-based metabolism may have been parts of purine nucleotide metabolism, while previous metabolic pathways were a part of the ancient RNA world.

上述代谢的主要途径，如糖酵解和柠檬酸循环，存在于生物的全部三个领域中，并存在于最后的普遍共同祖先中。这种普遍的祖先细胞是原核生物<ref name=SmithE/><ref>{{cite journal | vauthors = Romano AH, Conway T | title = Evolution of carbohydrate metabolic pathways | journal = Research in Microbiology | volume = 147 | issue = 6–7 | pages = 448–55 | year = 1996 | pmid = 9084754 | doi = 10.1016/0923-2508(96)83998-2 }}</ref>，也许是一种具有广泛的氨基酸、核苷酸、碳水化合物和脂质代谢的产烷菌<ref>{{cite book |author=Koch A |title=How did bacteria come to be? |journal=Adv Microb Physiol |volume=40 |pages=353–99 |year=1998 |pmid=9889982 |doi=10.1016/S0065-2911(08)60135-6 |series=Advances in Microbial Physiology |isbn=978-0-12-027740-7}}</ref><ref>{{cite journal | vauthors = Ouzounis C, Kyrpides N | title = The emergence of major cellular processes in evolution | journal = FEBS Letters | volume = 390 | issue = 2 | pages = 119–23 | date = July 1996 | pmid = 8706840 | doi = 10.1016/0014-5793(96)00631-X | s2cid = 39128865 }}</ref>。在后来的进化过程中，这些古老的途径之所以得以保留，可能是因为这些反应为它们特定的代谢问题提供了最佳解决方案，这些途径（如糖酵解和三羧酸循环）以最少的步骤高效地产生它们的最终产物。最初的基于酶的代谢途径可能是嘌呤核苷酸代谢的一部分<ref name=Ebenhoh/><ref name=Cascante/>，而之前的代谢途径是远古RNA界的一部分<ref>{{cite journal | vauthors = Caetano-Anollés G, Kim HS, Mittenthal JE | title = The origin of modern metabolic networks inferred from phylogenomic analysis of protein architecture | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 104 | issue = 22 | pages = 9358–63 | date = May 2007 | pmid = 17517598 | pmc = 1890499 | doi = 10.1073/pnas.0701214104 | bibcode = 2007PNAS..104.9358C }}</ref>。

Many models have been proposed to describe the mechanisms by which novel metabolic pathways evolve. These include the sequential addition of novel enzymes to a short ancestral pathway, the duplication and then divergence of entire pathways as well as the recruitment of pre-existing enzymes and their assembly into a novel reaction pathway. The relative importance of these mechanisms is unclear, but genomic studies have shown that enzymes in a pathway are likely to have a shared ancestry, suggesting that many pathways have evolved in a step-by-step fashion with novel functions created from pre-existing steps in the pathway. An alternative model comes from studies that trace the evolution of proteins' structures in metabolic networks, this has suggested that enzymes are pervasively recruited, borrowing enzymes to perform similar functions in different metabolic pathways (evident in the [[MANET database]]). These recruitment processes result in an evolutionary enzymatic mosaic. A third possibility is that some parts of metabolism might exist as "modules" that can be reused in different pathways and perform similar functions on different molecules.

Many models have been proposed to describe the mechanisms by which novel metabolic pathways evolve. These include the sequential addition of novel enzymes to a short ancestral pathway, the duplication and then divergence of entire pathways as well as the recruitment of pre-existing enzymes and their assembly into a novel reaction pathway. The relative importance of these mechanisms is unclear, but genomic studies have shown that enzymes in a pathway are likely to have a shared ancestry, suggesting that many pathways have evolved in a step-by-step fashion with novel functions created from pre-existing steps in the pathway. An alternative model comes from studies that trace the evolution of proteins' structures in metabolic networks, this has suggested that enzymes are pervasively recruited, borrowing enzymes to perform similar functions in different metabolic pathways (evident in the MANET database) These recruitment processes result in an evolutionary enzymatic mosaic. A third possibility is that some parts of metabolism might exist as "modules" that can be reused in different pathways and perform similar functions on different molecules.

人们提出了许多模型来描述新代谢途径的演变机制。其中包括将新的酶顺序添加到一个短的祖传途径，整个途径的复制和分化，吸纳原有的酶或者把这些机制组装成新的反应途径。这些机制的相对重要性尚不清楚<ref>{{cite journal | vauthors = Schmidt S, Sunyaev S, Bork P, Dandekar T | title = Metabolites: a helping hand for pathway evolution? | journal = Trends in Biochemical Sciences | volume = 28 | issue = 6 | pages = 336–41 | date = June 2003 | pmid = 12826406 | doi = 10.1016/S0968-0004(03)00114-2 }}</ref>，但基因组研究表明，一条途径中的酶很可能有共同的祖先，这意味着许多途径是逐步进化而来的，途径中预先存在的步骤创造出了新的功能。另一种模型来自于追踪代谢网络中蛋白质结构演化的研究<ref>{{cite journal | vauthors = Light S, Kraulis P | title = Network analysis of metabolic enzyme evolution in Escherichia coli | journal = BMC Bioinformatics | volume = 5 | pages = 15 | date = February 2004 | pmid = 15113413 | pmc = 394313 | doi = 10.1186/1471-2105-5-15 }} {{cite journal | vauthors = Alves R, Chaleil RA, Sternberg MJ | title = Evolution of enzymes in metabolism: a network perspective | journal = Journal of Molecular Biology | volume = 320 | issue = 4 | pages = 751–70 | date = July 2002 | pmid = 12095253 | doi = 10.1016/S0022-2836(02)00546-6 }}</ref>，它指出酶被普遍利用，生物体借用酶在不同的代谢途径中执行相似的功能(在 MANET 数据库中显而易见)<ref>{{cite journal | vauthors = Kim HS, Mittenthal JE, Caetano-Anollés G | title = MANET: tracing evolution of protein architecture in metabolic networks | journal = BMC Bioinformatics | volume = 7 | pages = 351 | date = July 2006 | pmid = 16854231 | pmc = 1559654 | doi = 10.1186/1471-2105-7-351 }}</ref>。这些征用过程导致了进化酶的嵌合<ref>{{cite journal | vauthors = Teichmann SA, Rison SC, Thornton JM, Riley M, Gough J, Chothia C | title = Small-molecule metabolism: an enzyme mosaic | journal = Trends in Biotechnology | volume = 19 | issue = 12 | pages = 482–6 | date = December 2001 | pmid = 11711174 | doi = 10.1016/S0167-7799(01)01813-3 }}</ref>。第三种可能性是，新陈代谢的某些部分可能作为“模块”存在，可以在不同的途径中重复使用，并对不同的分子执行类似的功能<ref>{{cite journal | vauthors = Spirin V, Gelfand MS, Mironov AA, Mirny LA | title = A metabolic network in the evolutionary context: multiscale structure and modularity | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 103 | issue = 23 | pages = 8774–9 | date = June 2006 | pmid = 16731630 | pmc = 1482654 | doi = 10.1073/pnas.0510258103 | bibcode = 2006PNAS..103.8774S }}</ref>。

As well as the evolution of new metabolic pathways, evolution can also cause the loss of metabolic functions. For example, in some [[parasite]]s metabolic processes that are not essential for survival are lost and preformed amino acids, nucleotides and carbohydrates may instead be scavenged from the [[host (biology)|host]]. Similar reduced metabolic capabilities are seen in [[endosymbiont|endosymbiotic]] organisms.

As well as the evolution of new metabolic pathways, evolution can also cause the loss of metabolic functions. For example, in some parasites metabolic processes that are not essential for survival are lost and preformed amino acids, nucleotides and carbohydrates may instead be scavenged from the host. Similar reduced metabolic capabilities are seen in endosymbiotic organisms.

除了新的代谢途径的进化，演化也会导致代谢功能的丧失。例如，在某些寄生物中，一些并非生存必需的代谢过程丢失了，而预先形成的氨基酸、核苷酸和碳水化合物可能会从寄主那里被清除<ref>{{cite journal | vauthors = Lawrence JG | title = Common themes in the genome strategies of pathogens | journal = Current Opinion in Genetics & Development | volume = 15 | issue = 6 | pages = 584–8 | date = December 2005 | pmid = 16188434 | doi = 10.1016/j.gde.2005.09.007 }} {{cite journal | vauthors = Wernegreen JJ | title = For better or worse: genomic consequences of intracellular mutualism and parasitism | journal = Current Opinion in Genetics & Development | volume = 15 | issue = 6 | pages = 572–83 | date = December 2005 | pmid = 16230003 | doi = 10.1016/j.gde.2005.09.013 }}</ref>。在内共生生物体中也可以看到类似的代谢能力下降<ref>{{cite journal | vauthors = Pál C, Papp B, Lercher MJ, Csermely P, Oliver SG, Hurst LD | title = Chance and necessity in the evolution of minimal metabolic networks | journal = Nature | volume = 440 | issue = 7084 | pages = 667–70 | date = March 2006 | pmid = 16572170 | doi = 10.1038/nature04568 | s2cid = 4424895 | bibcode = 2006Natur.440..667P }}</ref>。

==Investigation and manipulation==
调查和操纵
{{further|Protein methods|Proteomics|Metabolomics|Metabolic network modelling}}

更多信息：蛋白质方法，蛋白质组学，代谢组学和代谢网络建模

[[File:A thaliana metabolic network.png|thumb|upright=1.35|right|[[拟南芥]][[三羧酸循环]]的[[代谢网络]]。[[酶]]和[[代谢物]]显示为红色方块，它们之间的相互作用显示为黑线。]]

Classically, metabolism is studied by a [[reductionism|reductionist]] approach that focuses on a single metabolic pathway. Particularly valuable is the use of [[radioactive tracer]]s at the whole-organism, tissue and cellular levels, which define the paths from precursors to final products by identifying radioactively labelled intermediates and products. The enzymes that catalyze these chemical reactions can then be [[protein purification|purified]] and their [[enzyme kinetics|kinetics]] and responses to [[enzyme inhibitor|inhibitors]] investigated. A parallel approach is to identify the small molecules in a cell or tissue; the complete set of these molecules is called the [[metabolome]]. Overall, these studies give a good view of the structure and function of simple metabolic pathways, but are inadequate when applied to more complex systems such as the metabolism of a complete cell.

Classically, metabolism is studied by a reductionist approach that focuses on a single metabolic pathway. Particularly valuable is the use of radioactive tracers at the whole-organism, tissue and cellular levels, which define the paths from precursors to final products by identifying radioactively labelled intermediates and products. The enzymes that catalyze these chemical reactions can then be purified and their kinetics and responses to inhibitors investigated. A parallel approach is to identify the small molecules in a cell or tissue; the complete set of these molecules is called the metabolome. Overall, these studies give a good view of the structure and function of simple metabolic pathways, but are inadequate when applied to more complex systems such as the metabolism of a complete cell.

传统上，新陈代谢的研究采用还原法，侧重于单一的新陈代谢途径。特别有价值的是在整个有机体、组织和细胞水平上使用放射性示踪剂，通过追踪携带放射性标记的中间物和产品来获知从前体到最终产品的路径<ref>{{cite journal | vauthors = Rennie MJ | title = An introduction to the use of tracers in nutrition and metabolism | journal = The Proceedings of the Nutrition Society | volume = 58 | issue = 4 | pages = 935–44 | date = November 1999 | pmid = 10817161 | doi = 10.1017/S002966519900124X | doi-access = free }}</ref>。然后可以纯化催化这些化学反应的酶，并研究其动力学和对抑制剂的反应。一个并行的方法是识别细胞或组织中的小分子；这些分子的完整集合被称为代谢组。总的来说，这些研究可以很好地了解简单代谢途径的结构和功能，但当应用于更复杂的系统（如一个完整细胞的代谢时），这些研究是不够的<ref>{{cite journal | vauthors = Phair RD | title = Development of kinetic models in the nonlinear world of molecular cell biology | journal = Metabolism | volume = 46 | issue = 12 | pages = 1489–95 | date = December 1997 | pmid = 9439549 | doi = 10.1016/S0026-0495(97)90154-2 }}</ref>。

An idea of the complexity of the [[metabolic network]]s in cells that contain thousands of different enzymes is given by the figure showing the interactions between just 43 proteins and 40 metabolites to the right: the sequences of genomes provide lists containing anything up to 26.500 genes. However, it is now possible to use this genomic data to reconstruct complete networks of biochemical reactions and produce more [[Holism|holistic]] mathematical models that may explain and predict their behavior. These models are especially powerful when used to integrate the pathway and metabolite data obtained through classical methods with data on [[gene expression]] from [[proteomics|proteomic]] and [[DNA microarray]] studies. Using these techniques, a model of human metabolism has now been produced, which will guide future drug discovery and biochemical research. These models are now used in [[Network theory|network analysis]], to classify human diseases into groups that share common proteins or metabolites.

An idea of the complexity of the metabolic networks in cells that contain thousands of different enzymes is given by the figure showing the interactions between just 43 proteins and 40 metabolites to the right: the sequences of genomes provide lists containing anything up to 26.500 genes. However, it is now possible to use this genomic data to reconstruct complete networks of biochemical reactions and produce more holistic mathematical models that may explain and predict their behavior. These models are especially powerful when used to integrate the pathway and metabolite data obtained through classical methods with data on gene expression from proteomic and DNA microarray studies. Using these techniques, a model of human metabolism has now been produced, which will guide future drug discovery and biochemical research. These models are now used in network analysis, to classify human diseases into groups that share common proteins or metabolites.

细胞中包含数千种不同酶的代谢网络，这种复杂性概念可以在右图中看到，右图显示了43种蛋白质和40种代谢物之间的相互作用: 基因组序列提供了包含26.500个基因的列表<ref>{{cite journal | vauthors = Sterck L, Rombauts S, Vandepoele K, Rouzé P, Van de Peer Y | title = How many genes are there in plants (... and why are they there)? | journal = Current Opinion in Plant Biology | volume = 10 | issue = 2 | pages = 199–203 | date = April 2007 | pmid = 17289424 | doi = 10.1016/j.pbi.2007.01.004 }}</ref>。然而，现在能够利用这些基因组数据来重建完整的生化反应网络，并产生更全面的数学模型来解释和预测它们的行为。这些模型在用于整合通过经典方法获得的途径和代谢物数据以及蛋白质组学和DNA微阵列研究的基因表达数据时特别强大<ref>{{cite journal | vauthors = Borodina I, Nielsen J | title = From genomes to in silico cells via metabolic networks | journal = Current Opinion in Biotechnology | volume = 16 | issue = 3 | pages = 350–5 | date = June 2005 | pmid = 15961036 | doi = 10.1016/j.copbio.2005.04.008 }}</ref>。利用这些技术<ref>{{cite journal | vauthors = Gianchandani EP, Brautigan DL, Papin JA | title = Systems analyses characterize integrated functions of biochemical networks | journal = Trends in Biochemical Sciences | volume = 31 | issue = 5 | pages = 284–91 | date = May 2006 | pmid = 16616498 | doi = 10.1016/j.tibs.2006.03.007 }}</ref>，目前已经产生了一个人类代谢的模型，这将指导未来的药物发现和生化研究。这些模型现在被用于网络分析<ref>{{cite journal | vauthors = Duarte NC, Becker SA, Jamshidi N, Thiele I, Mo ML, Vo TD, Srivas R, Palsson BØ | display-authors = 6 | title = Global reconstruction of the human metabolic network based on genomic and bibliomic data | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 104 | issue = 6 | pages = 1777–82 | date = February 2007 | pmid = 17267599 | pmc = 1794290 | doi = 10.1073/pnas.0610772104 | bibcode = 2007PNAS..104.1777D }}</ref>，将人类疾病划分为具有共同蛋白质或代谢物的群体<ref>{{cite journal | vauthors = Goh KI, Cusick ME, Valle D, Childs B, Vidal M, Barabási AL | title = The human disease network | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 104 | issue = 21 | pages = 8685–90 | date = May 2007 | pmid = 17502601 | pmc = 1885563 | doi = 10.1073/pnas.0701361104 | bibcode = 2007PNAS..104.8685G }}</ref><ref>{{cite journal | vauthors = Lee DS, Park J, Kay KA, Christakis NA, Oltvai ZN, Barabási AL | title = The implications of human metabolic network topology for disease comorbidity | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 105 | issue = 29 | pages = 9880–5 | date = July 2008 | pmid = 18599447 | pmc = 2481357 | doi = 10.1073/pnas.0802208105 | url = http://www.pnas.org/lookup/pmid?view=long&pmid=18599447 | bibcode = 2008PNAS..105.9880L }}</ref>。

Bacterial metabolic networks are a striking example of [[Bow tie (biology)|bow-tie]] organization, an architecture able to input a wide range of nutrients and produce a large variety of products and complex macromolecules using a relatively few intermediate common currencies.

Bacterial metabolic networks are a striking example of bow-tie organization, an architecture able to input a wide range of nutrients and produce a large variety of products and complex macromolecules using a relatively few intermediate common currencies.

细菌代谢网络是蝴蝶结结构<ref name="pmid15331224">{{cite journal | vauthors = Csete M, Doyle J | title = Bow ties, metabolism and disease | journal = Trends in Biotechnology | volume = 22 | issue = 9 | pages = 446–50 | date = September 2004 | pmid = 15331224 | pmc = | doi = 10.1016/j.tibtech.2004.07.007 }}</ref><ref name="PMID12874056">{{cite journal | vauthors = Ma HW, Zeng AP | title = The connectivity structure, giant strong component and centrality of metabolic networks | journal = Bioinformatics | volume = 19 | issue = 11 | pages = 1423–30 | date = July 2003 | pmid = 12874056 | doi = 10.1093/bioinformatics/btg177 | citeseerx = 10.1.1.605.8964 }}</ref><ref name="PMID16916470">{{cite journal | vauthors = Zhao J, Yu H, Luo JH, Cao ZW, Li YX | title = Hierarchical modularity of nested bow-ties in metabolic networks | journal = BMC Bioinformatics | volume = 7 | pages = 386 | date = August 2006 | pmid = 16916470 | pmc = 1560398 | doi = 10.1186/1471-2105-7-386 | arxiv = q-bio/0605003 | bibcode = 2006q.bio.....5003Z }}</ref>的一个突出例子，这种架构能够输入多种营养物质，并利用相对较少的中间通货生产出大量产品和复杂的大分子。

A major technological application of this information is [[metabolic engineering]]. Here, organisms such as [[yeast]], plants or [[bacteria]] are genetically modified to make them more useful in [[biotechnology]] and aid the production of [[drug]]s such as [[antibiotic]]s or industrial chemicals such as [[1,3-Propanediol|1,3-propanediol]] and [[shikimic acid]]. These genetic modifications usually aim to reduce the amount of energy used to produce the product, increase yields and reduce the production of wastes.

A major technological application of this information is metabolic engineering. Here, organisms such as yeast, plants or bacteria are genetically modified to make them more useful in biotechnology and aid the production of drugs such as antibiotics or industrial chemicals such as 1,3-propanediol and shikimic acid. These genetic modifications usually aim to reduce the amount of energy used to produce the product, increase yields and reduce the production of wastes.

这些信息的一个主要技术应用是代谢工程学。在应用中，酵母、植物或细菌等生物体都可经过基因改造，使它们在生物技术方面更有用处，同时有助于生产抗生素等药物或工业化学品（如1,3- 丙二醇和莽草酸）<ref>{{cite journal | vauthors = Thykaer J, Nielsen J | title = Metabolic engineering of beta-lactam production | journal = Metabolic Engineering | volume = 5 | issue = 1 | pages = 56–69 | date = January 2003 | pmid = 12749845 | doi = 10.1016/S1096-7176(03)00003-X }}
{{cite journal | vauthors = González-Pajuelo M, Meynial-Salles I, Mendes F, Andrade JC, Vasconcelos I, Soucaille P | title = Metabolic engineering of Clostridium acetobutylicum for the industrial production of 1,3-propanediol from glycerol | journal = Metabolic Engineering | volume = 7 | issue = 5–6 | pages = 329–36 | year = 2005 | pmid = 16095939 | doi = 10.1016/j.ymben.2005.06.001 | hdl-access = free | hdl = 10400.14/3388 }}
{{cite journal | vauthors = Krämer M, Bongaerts J, Bovenberg R, Kremer S, Müller U, Orf S, Wubbolts M, Raeven L | display-authors = 6 | title = Metabolic engineering for microbial production of shikimic acid | journal = Metabolic Engineering | volume = 5 | issue = 4 | pages = 277–83 | date = October 2003 | pmid = 14642355 | doi = 10.1016/j.ymben.2003.09.001 }}</ref>。这些基因改造通常旨在减少生产产品所使用的能源，提高产量和减少废物的产生<ref>{{cite journal | vauthors = Koffas M, Roberge C, Lee K, Stephanopoulos G | title = Metabolic engineering | journal = Annual Review of Biomedical Engineering | volume = 1 | issue = | pages = 535–57 | year = 1999 | pmid = 11701499 | doi = 10.1146/annurev.bioeng.1.1.535 | s2cid = 11814282 }}</ref>。

==History==
历史
{{further|History of biochemistry|History of molecular biology}}

更多信息：生物化学的历史和分子生物学的历史

The term ''metabolism'' is derived from [[French language|French]] "métabolisme" or [[Ancient Greek]] μεταβολή – "Metabole" for "a change" which derived from μεταβάλλ –"Metaballein" means "To change"

The term metabolism is derived from French "métabolisme" or Ancient Greek μεταβολή – "Metabole" for "a change" which derived from μεταβάλλ –"Metaballein" means "To change"

新陈代谢这一术语源于法语“ métabolisme”或古希腊语 μταβoλλ -“Metabole”意为某种改变，它源自意为“去改变”的“ Metaballein”<ref>{{Cite web|title=metabolism {{!}} Origin and meaning of metabolism by Online Etymology Dictionary|url=https://www.etymonline.com/word/metabolism|access-date=2020-07-23|website=www.etymonline.com|language=en}}</ref>

[[File:Aristotle's metabolism.png|thumb|right|upright=1.4|亚里士多德Aristotle的新陈代谢是一个开放性的流动模型。]]

===Greek philosophy===
希腊哲学
[[Aristotle]]'s ''[[The Parts of Animals]]'' sets out enough details of [[Aristotle's biology|his views on metabolism]] for an open flow model to be made. He believed that at each stage of the process, materials from food were transformed, with heat being released as the [[classical element]] of fire, and residual materials being excreted as urine, bile, or faeces.

Aristotle's The Parts of Animals sets out enough details of his views on metabolism for an open flow model to be made. He believed that at each stage of the process, materials from food were transformed, with heat being released as the classical element of fire, and residual materials being excreted as urine, bile, or faeces.

Aristotle的《动物的各部分》详细阐述了他关于新陈代谢的观点，以便建立一个开放性的流动模型。他认为，在这个过程的每个阶段，来自食物的物质都会发生转化，释放出的热量成为火的典型元素，残余物质以尿液、胆汁或粪便的形式排出体外<ref>{{cite book|author=Leroi, Armand Marie|url=https://archive.org/stream/lagoonhowaristot0000lero?ref=ol#page/402/mode/2up|title=The Lagoon: How Aristotle Invented Science|date=2014|publisher=Bloomsbury|isbn=978-1-4088-3622-4|location=|pages=400–401|authorlink=Armand Marie Leroi}}</ref>。

===Islamic medicine===
伊斯兰医学
[[Ibn al-Nafis]] described metabolism in his 1260 AD work titled [[Al-Risalah al-Kamiliyyah fil Siera al-Nabawiyyah]] (The Treatise of Kamil on the Prophet's Biography) which included the following phrase "Both the body and its parts are in a continuous state of dissolution and nourishment, so they are inevitably undergoing permanent change."

Ibn al-Nafis described metabolism in his 1260 AD work titled Al-Risalah al-Kamiliyyah fil Siera al-Nabawiyyah (The Treatise of Kamil on the Prophet's Biography) which included the following phrase "Both the body and its parts are in a continuous state of dissolution and nourishment, so they are inevitably undergoing permanent change."

伊本·纳菲斯 Ibn al-Nafis 在其公元1260年的著作《 Al-Risalah al-Kamiliyyah fil Siera al-Nabawiyyah 》(《卡米尔关于先知传记的论述》)中描述了新陈代谢，其中包括以下短语: ”身体及其部分处于持续的溶解和营养状态，因此它们不可避免地要经历永久性的变化<ref>{{cite conference | vauthors = Al-Roubi AS | date = 1982 | title = Ibn Al-Nafis as a philosopher | conference = Symposium on Ibn al-Nafis, Second International Conference on Islamic Medicine | publisher = Islamic Medical Organization | location = Kuwait }} (cf. Ibn al-Nafis As a Philosopher, Encyclopedia of Islamic World [1])</ref>。

===Application of the scientific method===
科学方法的应用
The history of the scientific study of metabolism spans several centuries and has moved from examining whole animals in early studies, to examining individual metabolic reactions in modern biochemistry. The first controlled [[experiment]]s in human metabolism were published by [[Santorio Santorio]] in 1614 in his book ''Ars de statica medicina''. He described how he weighed himself before and after eating, [[sleeping|sleep]], working, sex, fasting, drinking, and excreting. He found that most of the food he took in was lost through what he called "[[insensible perspiration]]".

The history of the scientific study of metabolism spans several centuries and has moved from examining whole animals in early studies, to examining individual metabolic reactions in modern biochemistry. The first controlled experiments in human metabolism were published by Santorio Santorio in 1614 in his book Ars de statica medicina. He described how he weighed himself before and after eating, sleep, working, sex, fasting, drinking, and excreting. He found that most of the food he took in was lost through what he called "insensible perspiration".

新陈代谢的科学研究历史跨越了几个世纪，从早期研究中对动物整体的研究，到现代生物化学中对单个代谢反应的研究。人类新陈代谢的第一个对照实验是由圣托里奥·桑托里奥 Santorio Santorio于1614年在他的著作《静态医学》中发表的<ref>{{cite journal | vauthors = Eknoyan G | title = Santorio Sanctorius (1561-1636) - founding father of metabolic balance studies | journal = American Journal of Nephrology | volume = 19 | issue = 2 | pages = 226–33 | year = 1999 | pmid = 10213823 | doi = 10.1159/000013455 | s2cid = 32900603 }}</ref>。他描述了自己在进食、睡觉、工作、性交、禁食、饮水和排泄前后的体重。他发现他摄入的大部分食物都是通过他所谓的“无知觉的汗液”流失的。

[[File:SantoriosMeal.jpg|thumb|right|upright=0.7|Santorio Santorio 在他的杆秤上，来自静态医学，1614年首次发表]]

In these early studies, the mechanisms of these metabolic processes had not been identified and a [[vitalism|vital force]] was thought to animate living tissue. In the 19th century, when studying the [[fermentation (food)|fermentation]] of sugar to [[ethanol|alcohol]] by [[yeast]], [[Louis Pasteur]] concluded that fermentation was catalyzed by substances within the yeast cells he called "ferments". He wrote that "alcoholic fermentation is an act correlated with the life and organization of the yeast cells, not with the death or putrefaction of the cells." This discovery, along with the publication by [[Friedrich Woehler|Friedrich Wöhler]] in 1828 of a paper on the chemical synthesis of [[urea]], and is notable for being the first organic compound prepared from wholly inorganic precursors. This proved that the organic compounds and chemical reactions found in cells were no different in principle than any other part of chemistry.

In these early studies, the mechanisms of these metabolic processes had not been identified and a vital force was thought to animate living tissue. In the 19th century, when studying the fermentation of sugar to alcohol by yeast, Louis Pasteur concluded that fermentation was catalyzed by substances within the yeast cells he called "ferments". He wrote that "alcoholic fermentation is an act correlated with the life and organization of the yeast cells, not with the death or putrefaction of the cells." This discovery, along with the publication by Friedrich Wöhler in 1828 of a paper on the chemical synthesis of urea, and is notable for being the first organic compound prepared from wholly inorganic precursors. This proved that the organic compounds and chemical reactions found in cells were no different in principle than any other part of chemistry.

在早期的研究中，这些新陈代谢过程的机制还没有确定，人们认为一种生命力量是生命组织的活力<ref>{{cite book|url=https://archive.org/details/historyofscience04willuoft/page/n7/mode/2up|title=Modern Development of the Chemical and Biological Sciences|vauthors=Williams HA|date=1904|publisher=Harper and Brothers|isbn=|series=A History of Science: in Five Volumes|volume=IV|location=New York|pages=184–185|access-date=26 March 2007}}</ref>。19世纪，路易-巴斯德Louis Pasteur 在研究酵母菌将糖发酵成酒精时，得出结论：发酵是由酵母细胞内的物质催化的，他称之为 "发酵物"。他写道："酒精发酵是与酵母细胞的生命和组织有关的行为，而与细胞的死亡或腐烂无关"。这一发现<ref>{{cite journal | vauthors = Manchester KL | title = Louis Pasteur (1822-1895)--chance and the prepared mind | journal = Trends in Biotechnology | volume = 13 | issue = 12 | pages = 511–5 | date = December 1995 | pmid = 8595136 | doi = 10.1016/S0167-7799(00)89014-9 }}</ref>连同1828年弗里德里希-沃勒Friedrich Wöhler 发表的一篇关于尿素化学合成的论文<ref>{{cite journal | vauthors = Kinne-Saffran E, Kinne RK | title = Vitalism and synthesis of urea. From Friedrich Wöhler to Hans A. Krebs | journal = American Journal of Nephrology | volume = 19 | issue = 2 | pages = 290–4 | year = 1999 | pmid = 10213830 | doi = 10.1159/000013463 | s2cid = 71727190 }}</ref>，因为是第一个完全由无机前体制备的有机化合物而引人注目。这证明了在细胞中发现的有机化合物和化学反应与化学的任何其他部分在原理上没有什么不同。

It was the discovery of [[enzyme]]s at the beginning of the 20th century by [[Eduard Buchner]] that separated the study of the chemical reactions of metabolism from the biological study of cells, and marked the beginnings of [[biochemistry]]. The mass of biochemical knowledge grew rapidly throughout the early 20th century. One of the most prolific of these modern biochemists was [[Hans Adolf Krebs|Hans Krebs]] who made huge contributions to the study of metabolism. He discovered the urea cycle and later, working with [[Hans Kornberg]], the citric acid cycle and the glyoxylate cycle. Modern biochemical research has been greatly aided by the development of new techniques such as [[chromatography]], [[X-ray diffraction]], [[NMR spectroscopy]], [[radioisotopic labelling]], [[electron microscope|electron microscopy]] and [[molecular dynamics]] simulations. These techniques have allowed the discovery and detailed analysis of the many molecules and metabolic pathways in cells.

It was the discovery of enzymes at the beginning of the 20th century by Eduard Buchner that separated the study of the chemical reactions of metabolism from the biological study of cells, and marked the beginnings of biochemistry. The mass of biochemical knowledge grew rapidly throughout the early 20th century. One of the most prolific of these modern biochemists was Hans Krebs who made huge contributions to the study of metabolism. He discovered the urea cycle and later, working with Hans Kornberg, the citric acid cycle and the glyoxylate cycle. Modern biochemical research has been greatly aided by the development of new techniques such as chromatography, X-ray diffraction, NMR spectroscopy, radioisotopic labelling, electron microscopy and molecular dynamics simulations. These techniques have allowed the discovery and detailed analysis of the many molecules and metabolic pathways in cells.

爱德华·布赫纳（Eduard Buchner）在20世纪初发现了酶，从而将新陈代谢的化学反应研究与细胞的生物学研究分离开来，这标志着生物化学的开始<ref>Eduard Buchner's 1907 [http://nobelprize.org/nobel_prizes/chemistry/laureates/1907/buchner-lecture.html Nobel lecture] at http://nobelprize.org Accessed 20 March 2007</ref>。整个20世纪早期，生物化学知识的总量迅速增长。汉斯·克雷布斯（Hans Krebs）是这些现代生物化学家中最多产的一位，他对新陈代谢的研究做出了巨大的贡献。他发现了尿素循环<ref>{{cite journal | vauthors = Kornberg H | title = Krebs and his trinity of cycles | journal = Nature Reviews. Molecular Cell Biology | volume = 1 | issue = 3 | pages = 225–8 | date = December 2000 | pmid = 11252898 | doi = 10.1038/35043073 | s2cid = 28092593 }}</ref>，后来又与汉斯·科恩伯格（Hans Kornberg）合作，发现了三羧酸循环和乙醛酸循环。色谱、x射线衍射、核磁共振光谱、放射性同位素标记、电子显微镜和分子动力学模拟等新技术的发展极大地助力了现代生化研究<ref>{{cite journal |vauthors=Krebs HA, Henseleit K |title=Untersuchungen über die Harnstoffbildung im tierkorper |journal=Z. Physiol. Chem. |volume=210 |issue=1–2 |pages=33–66 |year=1932 |doi=10.1515/bchm2.1932.210.1-2.33}} 
{{cite journal | vauthors = Krebs HA, Johnson WA | title = Metabolism of ketonic acids in animal tissues | journal = The Biochemical Journal | volume = 31 | issue = 4 | pages = 645–60 | date = April 1937 | pmid = 16746382 | pmc = 1266984 | doi = 10.1042/bj0310645 }}</ref><ref name=Kornberg/>。这些技术已经能够发现和详细分析细胞中的许多分子和代谢途径。

== See also ==
另请参见

{{Portal|Metabolism}}新陈代谢

* {{anli|Anthropogenic metabolism}}人类新陈代谢

* {{anli|Antimetabolite}}抗代谢物

* {{anli|Basal metabolic rate}}基础代谢率

* {{anli|Calorimetry}}量热学

* {{anli|Isothermal microcalorimetry}}等温微量热法

* {{anli|Inborn errors of metabolism}}先天性代谢缺陷

* {{anli|Iron–sulfur world hypothesis}}, Hypothetical scenario for the origin of life, ，a "metabolism first" theory of the [[origin of life]] 铁硫世界假说，生命起源的假想情景，一个"新陈代谢第一 "的生命起源理论
* {{anli|Metabolic disorder}}代谢紊乱
* [[Microphysiometry]]微观生理学
* {{anli|Primary nutritional groups}}主要营养组织
* {{annotated link|Respirometry}}呼吸测量法
* {{anli|Stream metabolism}}流代谢
* {{anli|Sulfur metabolism}}硫代谢
* {{anli|Specific dynamic action|Thermic effect of food}}食物的热效应
* {{anli|Urban metabolism}}城市代谢
* {{anli|Fluid balance|Water metabolism}}水代谢平衡
* {{anli|Overflow metabolism}}溢出代谢
* {{anli|Reactome}} Reactome –生物途径数据库
* {{anli|KEGG}} 京都基因与基因组百科全书(Kyoto Encyclopedia of Genes and Genomes)

== References ==

{{Reflist|30em}}

== Further reading ==

{{Library resources box

|onlinebooks=yes

|by=no

|lcheading=Metabolism

|label=Metabolism

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'''Introductory'''

{{refbegin}}

* {{cite book | vauthors = Rose S, Mileusnic R | title = The Chemistry of Life. | publisher = Penguin Press Science | date = 1999 | isbn = 0-14-027273-9 }}

* {{cite book | vauthors = Schneider EC, Sagan D | title = Into the Cool: Energy Flow, Thermodynamics, and Life. | publisher = University of Chicago Press | date = 2005 | isbn = 0-226-73936-8}}

* {{cite book | vauthors = Lane N | title = Oxygen: The Molecule that Made the World. | publisher = Oxford University Press | location= USA | date = 2004 | isbn = 0-19-860783-0 }}

{{refend}}

General information

一般资料

'''Advanced'''

{{refbegin}}

* {{cite book | vauthors = Price N, Stevens L | title = Fundamentals of Enzymology: Cell and Molecular Biology of Catalytic Proteins. | publisher = Oxford University Press | date = 1999 | isbn = 0-19-850229-X }}

* {{cite book | vauthors = Berg J, Tymoczko J, Stryer L | title = Biochemistry | publisher = W. H. Freeman and Company | date = 2002 | isbn = 0-7167-4955-6 }}

* {{cite book | vauthors = Cox M, Nelson DL | title = Lehninger Principles of Biochemistry. | publisher = Palgrave Macmillan | date = 2004 | isbn = 0-7167-4339-6 }}

Human metabolism

人体新陈代谢

* {{cite book | author-link1 = Thomas D. Brock | vauthors = Brock TD, Madigan MR, Martinko J, Parker J | title = Brock's Biology of Microorganisms. | publisher = Benjamin Cummings | date = 2002 | isbn = 0-13-066271-2 }}

* {{cite book | vauthors = Da Silva JJ, Williams RJ | title = The Biological Chemistry of the Elements: The Inorganic Chemistry of Life. | publisher = Clarendon Press | date = 1991 | isbn = 0-19-855598-9 }}

* {{cite book | vauthors = Nicholls DG, Ferguson SJ | title = Bioenergetics | publisher = Academic Press Inc. | date = 2002 | isbn = 0-12-518121-3 }}

* {{cite journal | vauthors = Wood HG | title = Life with CO or CO2 and H2 as a source of carbon and energy | journal = FASEB Journal | volume = 5 | issue = 2 | pages = 156–63 | date = February 1991 | pmid = 1900793 | doi = 10.1096/fasebj.5.2.1900793 | s2cid = 45967404 }}

Databases

数据库

{{refend}}

== External links ==

{{Wikiversity|Topic:Biochemistry}}

{{wikibooks}}

Metabolic pathways

代谢途径

{{Wiktionary}}

{{Commons category}}

'''General information'''

* {{Britannica|377325|Metabolism (biology)}}

* [https://web.archive.org/web/20050308172226/http://www.rpi.edu/dept/bcbp/molbiochem/MBWeb/mb1/MB1index.html The Biochemistry of Metabolism]

* [http://www.sparknotes.com/testprep/books/sat2/biology/ Sparknotes SAT biochemistry] Overview of biochemistry. School level.

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* [http://www.sciencegateway.org/resources/biologytext/index.html MIT Biology Hypertextbook] Undergraduate-level guide to molecular biology.

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'''Human metabolism'''

* [http://library.med.utah.edu/NetBiochem/titles.htm Topics in Medical Biochemistry] Guide to human metabolic pathways. School level.

* [http://themedicalbiochemistrypage.org/ THE Medical Biochemistry Page] Comprehensive resource on human metabolism.

'''Databases'''

* [http://www.expasy.org/cgi-bin/show_thumbnails.pl Flow Chart of Metabolic Pathways] at [[ExPASy]]

* [http://www.iubmb-nicholson.org/pdf/MetabolicPathways_6_17_04_.pdf IUBMB-Nicholson Metabolic Pathways Chart]

* [http://bioinformatics.charite.de/supercyp/ SuperCYP: Database for Drug-Cytochrome-Metabolism]

'''Metabolic pathways'''

* [http://www.genome.ad.jp/kegg/pathway/map/map01100.html Metabolism reference Pathway]

* {{webarchive |url=https://web.archive.org/web/*/helios.bto.ed.ac.uk/bto/microbes/nitrogen.htm |date=* |title=The Nitrogen cycle and Nitrogen fixation }}

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Category:Underwater diving physiology

类别: 水下潜水生理学

<noinclude>

This page was moved from [[wikipedia:en:Metabolism]]. Its edit history can be viewed at [[新陈代谢/edithistory]]</noinclude>

[[Category:待整理页面]]

新陈代谢

2021-08-01T06:30:05Z

Fernando：修改ref和配图说明

此词条由Solitude初步翻译。

{{short description|The set of life-sustaining chemical transformations within the cells of organisms }}

{{redirect|Cell metabolism|the journal|Cell Metabolism}}

{{about||the architectural movement|Metabolism (architecture)}}

{{pp-move|small=yes}}

{{Use dmy dates|date=August 2018}}

{{Biochemistry sidebar}}

[[File:Metabolism.png|thumb|细胞新陈代谢的简化图]]

[[File:ATP-3D-vdW.png|thumb|right|[[三磷酸腺苷]]的结构（ATP），它是能量代谢中的中枢中间体。]]

'''Metabolism''' ({{IPAc-en|m|ə|ˈ|t|æ|b|ə|l|ɪ|z|ə|m}}, from {{lang-el|μεταβολή}} ''metabolē'', "change") is the set of [[life]]-sustaining [[chemical reactions]] in [[organisms]]. The three main purposes of metabolism are: the conversion of food to [[energy]] to run cellular processes; the conversion of food/fuel to building blocks for [[protein]]s, [[lipid]]s, [[nucleic acid]]s, and some [[carbohydrate]]s; and the elimination of [[Metabolic waste|metabolic wastes]]. These [[enzyme]]-catalyzed reactions allow organisms to grow and reproduce, maintain their structures, and respond to their environments. (The word metabolism can also refer to the sum of all chemical reactions that occur in living organisms, including [[digestion]] and the transport of substances into and between different cells, in which case the above described set of reactions within the cells is called intermediary metabolism or intermediate metabolism).

Metabolism (/məˈtæbəlɪzəm/, from Greek: μεταβολή metabolē, "change") is the set of life-sustaining chemical reactions in organisms. The three main purposes of metabolism are: the conversion of food to energy to run cellular processes; the conversion of food/fuel to building blocks for proteins, lipids, nucleic acids, and some carbohydrates; and the elimination of metabolic wastes. These enzyme-catalyzed reactions allow organisms to grow and reproduce, maintain their structures, and respond to their environments. (The word metabolism can also refer to the sum of all chemical reactions that occur in living organisms, including digestion and the transport of substances into and between different cells, in which case the above described set of reactions within the cells is called intermediary metabolism or intermediate metabolism).

新陈代谢（/məˈtæbəlɪzəm/，来自希腊语：μεταβολή metabolē，"变化"）是生物体内维持生命的[[化学反应]]。新陈代谢的三个主要目的是：将食物转化为能量以运行细胞过程；将食物/燃料转化为[[蛋白质]]、[[脂类]]、[[核酸]]和一些[[碳水化合物]]的构件；以及消除[[代谢废物]]。这些酶催化的反应使生物体得以生长和繁殖，维持其结构，并对其环境作出反应。（新陈代谢这个词也可以指生物体内发生的所有化学反应的总和，包括消化和物质在细胞内以及不同细胞之间的运输，在这种情况下，上述细胞内的一系列反应称为中间代谢或中级代谢）。

Metabolic reactions may be categorized as ''[[catabolic]]'' – the ''breaking down'' of compounds (for example, the breaking down of glucose to pyruvate by [[cellular respiration]]); or ''[[anabolic]]'' – the ''building up'' ([[biosynthesis|synthesis]]) of compounds (such as proteins, carbohydrates, lipids, and nucleic acids). Usually, catabolism releases energy, and anabolism consumes energy.

Metabolic reactions may be categorized as catabolic – the breaking down of compounds (for example, the breaking down of glucose to pyruvate by cellular respiration); or anabolic – the building up (synthesis) of compounds (such as proteins, carbohydrates, lipids, and nucleic acids). Usually, catabolism releases energy, and anabolism consumes energy.

新陈代谢反应可分为[[分解代谢]]分解代谢-分解化合物(例如，通过[[细胞呼吸]]将葡萄糖分解为丙酮酸) ; 或合成代谢-合成化合物(例如蛋白质、碳水化合物、脂类和核酸)。通常，分解代谢释放能量，合成代谢消耗能量。

The chemical reactions of metabolism are organized into [[metabolic pathway]]s, in which one chemical is transformed through a series of steps into another chemical, each step being facilitated by a specific [[enzyme]]. Enzymes are crucial to metabolism because they allow organisms to drive desirable reactions that require [[energy]] that will not occur by themselves, by [[Coupling (physics)|coupling]] them to [[spontaneous process|spontaneous reactions]] that release energy. Enzymes act as [[Catalysis|catalysts]] – they allow a reaction to proceed more rapidly – and they also allow the [[Metabolic pathway#Regulation|regulation]] of the rate of a metabolic reaction, for example in response to changes in the [[cell (biology)|cell's]] environment or to [[cell signaling|signals]] from other cells.

The chemical reactions of metabolism are organized into metabolic pathways, in which one chemical is transformed through a series of steps into another chemical, each step being facilitated by a specific enzyme. Enzymes are crucial to metabolism because they allow organisms to drive desirable reactions that require energy that will not occur by themselves, by coupling them to spontaneous reactions that release energy. Enzymes act as catalysts – they allow a reaction to proceed more rapidly – and they also allow the regulation of the rate of a metabolic reaction, for example in response to changes in the cell's environment or to signals from other cells.

新陈代谢的化学反应被组织成代谢途径，在代谢途径中，一种化学物质通过一系列步骤转化为另一种化学物质，每一步都由特定的[[酶]]来推动。酶对新陈代谢至关重要，因为它们通过将生物体与释放能量的自发反应耦合，使生物体能够驱动需要能量的理想反应，而这些反应本身不会发生。酶起催化剂的作用——它们使反应进行得更快——它们还可以调节代谢反应的速率，例如对细胞环境的变化或其他细胞发出的信号作出反应。

The metabolic system of a particular organism determines which substances it will find [[nutrition|nutritious]] and which [[poison]]ous. For example, some [[prokaryote]]s use [[hydrogen sulfide]] as a nutrient, yet this gas is poisonous to animals. The [[basal metabolic rate]] of an organism is the measure of the amount of energy consumed by all of these chemical reactions.

The metabolic system of a particular organism determines which substances it will find nutritious and which poisonous. For example, some prokaryotes use hydrogen sulfide as a nutrient, yet this gas is poisonous to animals. The basal metabolic rate of an organism is the measure of the amount of energy consumed by all of these chemical reactions.

特定生物体的新陈代谢系统决定了哪些物质有营养，哪些有毒。例如，一些[[原核生物]]利用硫化氢作为营养物质，然而这种气体对动物是有毒的<ref name="Physiology1">{{cite book |author=Friedrich C |title=Physiology and genetics of sulfur-oxidizing bacteria |journal=Adv Microb Physiol |volume=39 |issue= |pages=235–89 |year=1998 |pmid=9328649 |doi=10.1016/S0065-2911(08)60018-1 |series=Advances in Microbial Physiology |isbn=978-0-12-027739-1}}</ref>。生物体的[[基础代谢率]]是所有这些化学反应所消耗能量的量度。

A striking feature of metabolism is the similarity of the basic metabolic pathways among vastly different species. For example, the set of [[carboxylic acid]]s that are best known as the intermediates in the [[citric acid cycle]] are present in all known organisms, being found in species as diverse as the [[Unicellular organism|unicellular]] bacterium ''[[Escherichia coli]]'' and huge [[multicellular organism]]s like [[elephant]]s. These similarities in metabolic pathways are likely due to their early appearance in [[evolutionary history of life|evolutionary history]], and their retention because of their [[efficacy]]. The metabolism of cancer cells is also different from the metabolism of normal cells and these differences can be used to find targets for therapeutic intervention in cancer.

A striking feature of metabolism is the similarity of the basic metabolic pathways among vastly different species. For example, the set of carboxylic acids that are best known as the intermediates in the citric acid cycle are present in all known organisms, being found in species as diverse as the unicellular bacterium Escherichia coli and huge multicellular organisms like elephants. These similarities in metabolic pathways are likely due to their early appearance in evolutionary history, and their retention because of their efficacy. The metabolism of cancer cells is also different from the metabolism of normal cells and these differences can be used to find targets for therapeutic intervention in cancer.

新陈代谢的一个显著特征是，不同物种之间的基本新陈代谢途径具有相似性<ref>{{cite journal | vauthors = Pace NR | title = The universal nature of biochemistry | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 98 | issue = 3 | pages = 805–8 | date = January 2001 | pmid = 11158550 | pmc = 33372 | doi = 10.1073/pnas.98.3.805 | bibcode = 2001PNAS...98..805P }}</ref>。例如，作为[[三羧酸循环]]中的中间体，最著名的一组羧酸存在于所有已知的生物体中，它们在单细胞细菌[[大肠杆菌]]和巨大的多细胞生物（如大象）中都能被找到<ref name=SmithE>{{cite journal | vauthors = Smith E, Morowitz HJ | title = Universality in intermediary metabolism | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 101 | issue = 36 | pages = 13168–73 | date = September 2004 | pmid = 15340153 | pmc = 516543 | doi = 10.1073/pnas.0404922101 | bibcode = 2004PNAS..10113168S }}</ref>。这些代谢途径的相似性很可能是由于它们在演化史的早期出现，然后又因为它们的功效而保留下来<ref name=Ebenhoh>{{cite journal | vauthors = Ebenhöh O, Heinrich R | title = Evolutionary optimization of metabolic pathways. Theoretical reconstruction of the stoichiometry of ATP and NADH producing systems | journal = Bulletin of Mathematical Biology | volume = 63 | issue = 1 | pages = 21–55 | date = January 2001 | pmid = 11146883 | doi = 10.1006/bulm.2000.0197 | s2cid = 44260374 }}</ref><ref name=Cascante>{{cite journal | vauthors = Meléndez-Hevia E, Waddell TG, Cascante M | title = The puzzle of the Krebs citric acid cycle: assembling the pieces of chemically feasible reactions, and opportunism in the design of metabolic pathways during evolution | journal = Journal of Molecular Evolution | volume = 43 | issue = 3 | pages = 293–303 | date = September 1996 | pmid = 8703096 | doi = 10.1007/BF02338838 | s2cid = 19107073 | bibcode = 1996JMolE..43..293M }}</ref>。癌细胞的代谢也不同于正常细胞的代谢，这些差异可以用来寻找癌细胞治疗的靶点<ref name="Vander_Heiden_2017">{{cite journal | vauthors = Vander Heiden MG, DeBerardinis RJ | title = Understanding the Intersections between Metabolism and Cancer Biology | journal = Cell | volume = 168 | issue = 4 | pages = 657–669 | date = February 2017 | pmid = 28187287 | pmc = 5329766 | doi = 10.1016/j.cell.2016.12.039 }}</ref>。

== Key biochemicals ==
关键的生物化学成分

{{further|Biomolecule|Cell (biology)|Biochemistry}}

更多信息：生物分子，细胞（生物学）和生物化学

[[File:Trimyristin-3D-vdW.png|right|thumb|upright=1.15|[[三酰甘油脂]]的结构]]

[[File:Human Metabolism - Pathways.jpg|thumb|这张图表描绘了人体新陈代谢的一系列途径。]]

Most of the structures that make up animals, plants and microbes are made from four basic classes of [[molecule]]: [[amino acid]]s, [[carbohydrate]]s , [[nucleic acid]] and [[lipid]]s (often called [[fat]]s). As these molecules are vital for life, metabolic reactions either focus on making these molecules during the construction of cells and tissues, or by breaking them down and using them as a source of energy, by their digestion. These biochemicals can be joined together to make [[polymer]]s such as [[DNA]] and [[protein]]s, essential [[macromolecules]] of life.

Most of the structures that make up animals, plants and microbes are made from four basic classes of molecule: amino acids, carbohydrates , nucleic acid and lipids (often called fats). As these molecules are vital for life, metabolic reactions either focus on making these molecules during the construction of cells and tissues, or by breaking them down and using them as a source of energy, by their digestion. These biochemicals can be joined together to make polymers such as DNA and proteins, essential macromolecules of life.

构成动物、植物和微生物的大部分结构由四种基本分子组成: 氨基酸、糖类化合物、核酸和脂类(通常称为脂肪)。由于这些分子对生命至关重要，新陈代谢反应要么专注于在构建细胞和组织的过程中制造这些分子，要么将这些分子作为能量来源并将其消化分解。这些生化物质可以结合在一起形成DNA和蛋白质之类的聚合物，它们都是生命必不可少的[[大分子聚合物]]<ref>{{cite journal|last=Cooper|first=Geoffrey M.| name-list-style = vanc |date=2000|title=The Molecular Composition of Cells|url=https://www.ncbi.nlm.nih.gov/books/NBK9879/|journal=The Cell: A Molecular Approach. 2nd Edition|language=en}}</ref>。

<center>
{| class=“wikitable” style = “margin-left: auto; margin-right: auto;”
|-
!分子类型 !! [[单体]]形式的名称 !! [[聚合物]]形式的名称 !! 聚合物形态的例子
|-
| 氨基酸 || [[蛋白质]](由多肽组成) || [[纤维蛋白]]和[[球状蛋白]]
|-
| [[碳水化合物]] || [[单糖]] || [[多糖]] || [[淀粉]], [[糖原]] and [[纤维素]]
|-
| [[核酸]] || [[核苷酸]] || [[多核苷酸]] || [[DNA]] and [[RNA]]
|}
</center>

===Amino acids and proteins===
氨基酸和蛋白质

[[Protein]]s are made of [[amino acid]]s arranged in a linear chain joined together by [[peptide bond]]s. Many proteins are [[enzyme]]s that [[catalysis|catalyze]] the chemical reactions in metabolism. Other proteins have structural or mechanical functions, such as those that form the [[cytoskeleton]], a system of [[scaffolding]] that maintains the cell shape.Proteins are also important in [[cell signaling]], [[antibody|immune responses]], [[cell adhesion]], [[active transport]] across membranes, and the [[cell cycle]].Amino acids also contribute to cellular energy metabolism by providing a carbon source for entry into the citric acid cycle ([[tricarboxylic acid cycle]]), especially when a primary source of energy, such as [[glucose]], is scarce, or when cells undergo metabolic stress.

Proteins are made of amino acids arranged in a linear chain joined together by peptide bonds. Many proteins are enzymes that catalyze the chemical reactions in metabolism. Other proteins have structural or mechanical functions, such as those that form the cytoskeleton, a system of scaffolding that maintains the cell shape. Proteins are also important in cell signaling, immune responses, cell adhesion, active transport across membranes, and the cell cycle. Amino acids also contribute to cellular energy metabolism by providing a carbon source for entry into the citric acid cycle (tricarboxylic acid cycle), especially when a primary source of energy, such as glucose, is scarce, or when cells undergo metabolic stress.

蛋白质是由氨基酸组成的线性链，它们通过[[肽键]]连接在一起。许多蛋白质是在新陈代谢中催化化学反应的酶。其他蛋白质具有结构或机械功能，例如那些形成[[细胞骨架]]的蛋白质（细胞骨架是维持细胞形状的支架系统）<ref>{{cite journal | vauthors = Michie KA, Löwe J | title = Dynamic filaments of the bacterial cytoskeleton | journal = Annual Review of Biochemistry | volume = 75 | issue = | pages = 467–92 | year = 2006 | pmid = 16756499 | doi = 10.1146/annurev.biochem.75.103004.142452 | s2cid = 4550126 }}</ref> 。蛋白质在[[细胞信号传导]]、[[免疫反应]]、[[细胞粘附]]、主动跨膜转运和[[细胞周期]]中也很重要<ref name=Nelson>{{cite book | last1 = Nelson | first1 = David L. | first2 = Michael M. | last2 = Cox | name-list-style = vanc | title = Lehninger Principles of Biochemistry | publisher = W. H. Freeman and company | year = 2005 | location = New York | page = [https://archive.org/details/lehningerprincip00lehn_0/page/841 841] | isbn = 978-0-7167-4339-2 | url-access = registration | url = https://archive.org/details/lehningerprincip00lehn_0/page/841 }}</ref> 。氨基酸还通过提供碳源进入细胞三羧酸循环，促进细胞的能量代谢，<ref>{{cite journal | vauthors = Kelleher JK, Bryan BM, Mallet RT, Holleran AL, Murphy AN, Fiskum G | title = Analysis of tricarboxylic acid-cycle metabolism of hepatoma cells by comparison of 14CO2 ratios | journal = The Biochemical Journal | volume = 246 | issue = 3 | pages = 633–9 | date = September 1987 | pmid = 3120698 | pmc = 1148327 | doi = 10.1042/bj2460633 }}</ref>尤其是在[[葡萄糖]]等主要能量来源匮乏或细胞发生代谢应激时<ref>{{cite journal | vauthors = Hothersall JS, Ahmed A | title = Metabolic fate of the increased yeast amino Acid uptake subsequent to catabolite derepression | journal = Journal of Amino Acids | volume = 2013 | pages = 461901 | year = 2013 | pmid = 23431419 | pmc = 3575661 | doi = 10.1155/2013/461901 }}</ref>。

===Lipids===
脂类
[[Lipid]]s are the most diverse group of biochemicals. Their main structural uses are as part of [[biological membrane]]s both internal and external, such as the [[cell membrane]], or as a source of energy. Lipids are usually defined as [[hydrophobe|hydrophobic]] or [[amphiphiles|amphipathic]] biological molecules but will dissolve in [[organic solvent]]s such as [[ethanol|alcohol]], [[benzene]] or [[chloroform]]. The [[fat]]s are a large group of compounds that contain [[fatty acid]]s and [[glycerol]]; a glycerol molecule attached to three fatty acid [[ester]]s is called a [[triglyceride|triacylglyceride]]. Several variations on this basic structure exist, including backbones such as [[sphingosine]] in the [[sphingomyelin]], and [[hydrophile|hydrophilic]] groups such as [[phosphate]] as in [[phospholipid]]s. [[Steroid]]s such as [[sterol]] are another major class of lipids.

Lipids are the most diverse group of biochemicals. Their main structural uses are as part of biological membranes both internal and external, such as the cell membrane, or as a source of energy. Lipids are usually defined as hydrophobic or amphipathic biological molecules but will dissolve in organic solvents such as alcohol, benzene or chloroform. The fats are a large group of compounds that contain fatty acids and glycerol; a glycerol molecule attached to three fatty acid esters is called a triacylglyceride. Several variations on this basic structure exist, including backbones such as sphingosine in the sphingomyelin, and hydrophilic groups such as phosphate as in phospholipids. Steroids such as sterol are another major class of lipids.

脂类是最多样化的生物化学物质。它们的主要结构用途是作为[[生物膜]]内部和外部的一部分，如[[细胞膜]]，或作为能量来源<ref name=Nelson/>。脂类通常被定义为疏水性或两亲性的生物分子，但会溶解在有机溶剂中，如酒精、苯或氯仿。<ref>{{cite journal | vauthors = Fahy E, Subramaniam S, Brown HA, Glass CK, Merrill AH, Murphy RC, Raetz CR, Russell DW, Seyama Y, Shaw W, Shimizu T, Spener F, van Meer G, VanNieuwenhze MS, White SH, Witztum JL, Dennis EA | display-authors = 6 | title = A comprehensive classification system for lipids | journal = Journal of Lipid Research | volume = 46 | issue = 5 | pages = 839–61 | date = May 2005 | pmid = 15722563 | doi = 10.1194/jlr.E400004-JLR200 | doi-access = free }}</ref>脂肪是一大类含有脂肪酸和甘油的化合物，一个甘油分子连接到三个脂肪酸酯即称为三酰甘油酯。<ref>{{cite web|title=Lipid nomenclature Lip-1 & Lip-2|url=https://www.qmul.ac.uk/sbcs/iupac/lipid/lip1n2.html#p11|access-date=2020-06-06|website=www.qmul.ac.uk}}</ref>这种基本结构存在一些变异，包括主骨(如鞘磷脂中到鞘氨醇)和亲水基(如磷脂中的磷酸盐)。[[类固醇]]，如[[固醇]]，是另一类主要的脂类<ref>{{cite book|edition=8|title=Biochemistry|location=New York|isbn=978-1-4641-2610-9|oclc=913469736 | vauthors = Berg JM, Tymoczko JL, Gatto Jr GJ, Stryer L |date=8 April 2015|publisher=W. H. Freeman|pages=362}}</ref>。

===Carbohydrates===
碳水化合物

[[File:Glucose Fisher to Haworth.gif|thumb|upright=1.15|right|alt=The straight chain form consists of four C H O H groups linked in a row, capped at the ends by an aldehyde group C O H and a methanol group C H 2 O H. To form the ring, the aldehyde group combines with the O H group of the next-to-last carbon at the other end, just before the methanol group.|[[Glucose]] can exist in both a straight-chain and ring form.]]

[[Glucose can exist in both a straight-chain and ring form.]]

[葡萄糖可以以直链和环的形式存在。]

[[Carbohydrate]]s are [[aldehyde]]s or [[ketone]]s, with many [[hydroxyl]] groups attached, that can exist as straight chains or rings. Carbohydrates are the most abundant biological molecules, and fill numerous roles, such as the storage and transport of [[energy]] ([[starch]], [[glycogen]]) and structural components ([[cellulose]] in plants, [[chitin]] in animals). The basic carbohydrate units are called [[monosaccharide]]s and include [[galactose]], [[fructose]], and most importantly [[glucose]]. Monosaccharides can be linked together to form [[polysaccharide]]s in almost limitless ways.

Carbohydrates are aldehydes or ketones, with many hydroxyl groups attached, that can exist as straight chains or rings. Carbohydrates are the most abundant biological molecules, and fill numerous roles, such as the storage and transport of energy (starch, glycogen) and structural components (cellulose in plants, chitin in animals). The basic carbohydrate units are called monosaccharides and include galactose, fructose, and most importantly glucose. Monosaccharides can be linked together to form polysaccharides in almost limitless ways.

碳水化合物是醛或酮，带有许多羟基，能以直链或环的形式存在。碳水化合物是最丰富的生物分子，承担着许多作用，如能量的储存和运输（淀粉、糖原）和作为结构要件（植物的纤维素、动物的甲壳素）。基本的碳水化合物单位称为单糖<ref name=Nelson/>，包括半乳糖、果糖以及最重要的葡萄糖。单糖能以几乎无限多样的方式连接在一起形成多糖<ref>{{cite journal | vauthors = Raman R, Raguram S, Venkataraman G, Paulson JC, Sasisekharan R | title = Glycomics: an integrated systems approach to structure-function relationships of glycans | journal = Nature Methods | volume = 2 | issue = 11 | pages = 817–24 | date = November 2005 | pmid = 16278650 | doi = 10.1038/nmeth807 | s2cid = 4644919 }}</ref>。

===Nucleotides===

核苷酸
The two nucleic acids, DNA and [[RNA]], are polymers of [[nucleotide]]s. Each nucleotide is composed of a phosphate attached to a [[ribose]] or [[deoxyribose]] sugar group which is attached to a [[nitrogenous base]]. Nucleic acids are critical for the storage and use of genetic information, and its interpretation through the processes of [[transcription (genetics)|transcription]] and [[protein biosynthesis]]. This information is protected by [[DNA repair]] mechanisms and propagated through [[DNA replication]]. Many [[virus]]es have an [[RNA virus|RNA genome]], such as [[HIV]], which uses [[reverse transcription]] to create a DNA template from its viral RNA genome. RNA in [[ribozyme]]s such as [[spliceosome]]s and [[ribosome]]s is similar to enzymes as it can catalyze chemical reactions. Individual [[nucleoside]]s are made by attaching a [[nucleobase]] to a [[ribose]] sugar. These bases are [[heterocyclic]] rings cono ptaining nitrogen, classified as [[purine]]s or [[pyrimidine]]s. Nucleotides also act as coenzymes in metabolic-group-transfer reactions.

The two nucleic acids, DNA and RNA, are polymers of nucleotides. Each nucleotide is composed of a phosphate attached to a ribose or deoxyribose sugar group which is attached to a nitrogenous base. Nucleic acids are critical for the storage and use of genetic information, and its interpretation through the processes of transcription and protein biosynthesis.This information is protected by DNA repair mechanisms and propagated through DNA replication. Many viruses have an RNA genome, such as HIV, which uses reverse transcription to create a DNA template from its viral RNA genome.RNA in ribozymes such as spliceosomes and ribosomes is similar to enzymes as it can catalyze chemical reactions. Individual nucleosides are made by attaching a nucleobase to a ribose sugar. These bases are heterocyclic rings containing nitrogen, classified as purines or pyrimidines. Nucleotides also act as coenzymes in metabolic-group-transfer reactions.

DNA和RNA这两种核酸是核苷酸的聚合物。每个核苷酸都是由一个磷酸连接到核糖或脱氧核糖糖基上形成的，而核糖或脱氧核糖糖基又连接到含氮碱基上。核酸对于遗传信息的储存和使用，以及通过转录和蛋白质生物合成过程对其进行解释至关重要。这些信息受到DNA修复机制的保护<ref name=Nelson/>，并通过DNA复制进行传播。许多病毒都有RNA基因组，如HIV病毒，它利用[[逆转录]]从其病毒RNA基因组中创建DNA模板。核糖体和核糖体等核糖体中的RNA类似于酶<ref>{{cite journal | vauthors = Sierra S, Kupfer B, Kaiser R | title = Basics of the virology of HIV-1 and its replication | journal = Journal of Clinical Virology | volume = 34 | issue = 4 | pages = 233–44 | date = December 2005 | pmid = 16198625 | doi = 10.1016/j.jcv.2005.09.004 }}</ref>，因为它可以催化化学反应。单个核苷是通过将核碱基连接到核糖上制成的。这些碱基是含氮的杂环，分为嘌呤或嘧啶。核苷酸还在代谢基团转移反应中充当辅酶<ref name=Wimmer>{{cite journal | vauthors = Wimmer MJ, Rose IA | title = Mechanisms of enzyme-catalyzed group transfer reactions | journal = Annual Review of Biochemistry | volume = 47 | issue = | pages = 1031–78 | year = 1978 | pmid = 354490 | doi = 10.1146/annurev.bi.47.070178.005123 }}</ref>。

===Coenzymes===
辅酶

[[File:Acetyl-CoA-2D.svg|thumb|right|upright=1.35|Structure of the [[coenzyme]] [[acetyl-CoA]].The transferable [[acetyl|acetyl group]] is bonded to the sulfur atom at the extreme left.]]

Structure of the [[coenzyme acetyl-CoA.The transferable acetyl group is bonded to the sulfur atom at the extreme left.]]

[[辅酶乙酰辅酶结构 a。可转移的乙酰基与最左边的硫原子成键结合。]]

{{main|Coenzyme}}

Metabolism involves a vast array of chemical reactions, but most fall under a few basic types of reactions that involve the transfer of [[functional group]]s of atoms and their bonds within molecules. This common chemistry allows cells to use a small set of metabolic intermediates to carry chemical groups between different reactions. These group-transfer intermediates are called [[coenzyme]]s. Each class of group-transfer reactions is carried out by a particular coenzyme, which is the [[substrate (biochemistry)|substrate]] for a set of enzymes that produce it, and a set of enzymes that consume it. These coenzymes are therefore continuously made, consumed and then recycled.

Metabolism involves a vast array of chemical reactions, but most fall under a few basic types of reactions that involve the transfer of functional groups of atoms and their bonds within molecules. This common chemistry allows cells to use a small set of metabolic intermediates to carry chemical groups between different reactions. These group-transfer intermediates are called coenzymes. Each class of group-transfer reactions is carried out by a particular coenzyme, which is the substrate for a set of enzymes that produce it, and a set of enzymes that consume it. These coenzymes are therefore continuously made, consumed and then recycled.

新陈代谢涉及大量的化学反应，但大多数属于几种基本类型的反应，涉及原子的官能团及其键在分子内的转移。这种常见的化学反应使细胞能够用一小套代谢中间体在不同反应之间携带化学基团<ref>{{cite journal | vauthors = Mitchell P | title = The Ninth Sir Hans Krebs Lecture. Compartmentation and communication in living systems. Ligand conduction: a general catalytic principle in chemical, osmotic and chemiosmotic reaction systems | journal = European Journal of Biochemistry | volume = 95 | issue = 1 | pages = 1–20 | date = March 1979 | pmid = 378655 | doi = 10.1111/j.1432-1033.1979.tb12934.x }}</ref>。这些基团转移中间体称为辅酶<ref name=Wimmer/>。每一类基团转移反应都是由一种特定的辅酶进行的，它是一组产生它的酶和消耗它的酶的底物。因此，这些辅酶不断地被制造、消耗，然后循环利用<ref name=Dimroth>{{cite journal | vauthors = Dimroth P, von Ballmoos C, Meier T | title = Catalytic and mechanical cycles in F-ATP synthases. Fourth in the Cycles Review Series | journal = EMBO Reports | volume = 7 | issue = 3 | pages = 276–82 | date = March 2006 | pmid = 16607397 | pmc = 1456893 | doi = 10.1038/sj.embor.7400646 }}</ref>。

One central coenzyme is [[adenosine triphosphate]] (ATP), the universal energy currency of cells. This nucleotide is used to transfer chemical energy between different chemical reactions. There is only a small amount of ATP in cells, but as it is continuously regenerated, the human body can use about its own weight in ATP per day. ATP acts as a bridge between [[catabolism]] and [[anabolism]]. Catabolism breaks down molecules, and anabolism puts them together. Catabolic reactions generate ATP, and anabolic reactions consume it. It also serves as a carrier of phosphate groups in [[phosphorylation]] reactions.

One central coenzyme is adenosine triphosphate (ATP), the universal energy currency of cells. This nucleotide is used to transfer chemical energy between different chemical reactions. There is only a small amount of ATP in cells, but as it is continuously regenerated, the human body can use about its own weight in ATP per day. ATP acts as a bridge between catabolism and anabolism. Catabolism breaks down molecules, and anabolism puts them together. Catabolic reactions generate ATP, and anabolic reactions consume it. It also serves as a carrier of phosphate groups in phosphorylation reactions.

其中一种中心辅酶是三磷酸腺苷（ATP），它是细胞的通用能源货币。这种核苷酸在不同的化学反应之间传递化学能。细胞中只有少量的ATP，但由于ATP是不断再生的，所以人体每天可以使用大约相当于自身重量的ATP<ref name=Dimroth/>。ATP是分解代谢和合成代谢之间的桥梁。分解代谢分解分子，合成代谢则将它们组合在一起。分解反应产生ATP，合成代谢反应则消耗ATP。它也是磷酸化反应中磷酸基团的载体<ref>{{cite journal | vauthors = Bonora M, Patergnani S, Rimessi A, De Marchi E, Suski JM, Bononi A, Giorgi C, Marchi S, Missiroli S, Poletti F, Wieckowski MR, Pinton P | display-authors = 6 | title = ATP synthesis and storage | journal = Purinergic Signalling | volume = 8 | issue = 3 | pages = 343–57 | date = September 2012 | pmid = 22528680 | pmc = 3360099 | doi = 10.1007/s11302-012-9305-8 }}</ref>。

A [[vitamin]] is an organic compound needed in small quantities that cannot be made in cells. In [[human nutrition]], most vitamins function as coenzymes after modification; for example, all water-soluble vitamins are phosphorylated or are coupled to nucleotides when they are used in cells. [[Nicotinamide adenine dinucleotide]] (NAD+), a derivative of vitamin B3 ([[niacin]]), is an important coenzyme that acts as a hydrogen acceptor. Hundreds of separate types of [[dehydrogenase]]s remove electrons from their substrates and [[redox|reduce]] NAD+ into NADH. This reduced form of the coenzyme is then a substrate for any of the [[reductase]]s in the cell that need to reduce their substrates. Nicotinamide adenine dinucleotide exists in two related forms in the cell, NADH and NADPH. The NAD+/NADH form is more important in catabolic reactions, while NADP+/NADPH is used in anabolic reactions.

A vitamin is an organic compound needed in small quantities that cannot be made in cells. In human nutrition, most vitamins function as coenzymes after modification; for example, all water-soluble vitamins are phosphorylated or are coupled to nucleotides when they are used in cells. Nicotinamide adenine dinucleotide (NAD+), a derivative of vitamin B3 (niacin), is an important coenzyme that acts as a hydrogen acceptor. Hundreds of separate types of dehydrogenases remove electrons from their substrates and reduce NAD+ into NADH. This reduced form of the coenzyme is then a substrate for any of the reductases in the cell that need to reduce their substrates. Nicotinamide adenine dinucleotide exists in two related forms in the cell, NADH and NADPH. The NAD+/NADH form is more important in catabolic reactions, while NADP+/NADPH is used in anabolic reactions.

[[维生素]]是一类细胞不能合成的微量有机化合物。在人体营养中，大多数维生素经过修饰后都具有辅酶的功能，例如，所有水溶性维生素在细胞中使用时都会被磷酸化或与核苷酸偶联<ref>{{cite journal|last1=Berg|first1=Jeremy M.|last2=Tymoczko|first2=John L.|last3=Stryer|first3=Lubert | name-list-style = vanc |date=2002|title=Vitamins Are Often Precursors to Coenzymes|url=https://www.ncbi.nlm.nih.gov/books/NBK22549/|journal=Biochemistry. 5th Edition|language=en}}</ref>。[[烟酰胺腺嘌呤二核苷酸]](NAD+)是维生素B3(烟酸)的衍生物，它是一种重要的辅酶，起着氢接受器的作用。数百种不同类型的脱氢酶从其底物中去除电子，并将NAD+还原成NADH。这种还原形式的辅酶是细胞中任何需要还原其底物的还原酶的底物。烟酰胺腺嘌呤二核苷酸在细胞中以两种相关形式存在<ref>{{cite journal | vauthors = Pollak N, Dölle C, Ziegler M | title = The power to reduce: pyridine nucleotides--small molecules with a multitude of functions | journal = The Biochemical Journal | volume = 402 | issue = 2 | pages = 205–18 | date = March 2007 | pmid = 17295611 | pmc = 1798440 | doi = 10.1042/BJ20061638 }}</ref>，即NADH和NADPH。NAD +/NADH 形式在分解代谢反应中起重要作用，而 NADP +/NADPH 形式在分解代谢反应中起重要作用<ref>{{cite book|last=Fatih|first=Yildiz | name-list-style = vanc |title=Advances in food biochemistry|publisher=CRC Press|year=2009|isbn=978-1-4200-0769-5|location=Boca Raton|pages=228|oclc=607553259}}</ref>。

[[File:1GZX Haemoglobin.png|thumb|upright=1.35|right|The structure of iron-containing [[hemoglobin]]. The protein subunits are in red and blue, and the iron-containing [[heme]] groups in green. From {{PDB|1GZX}}.]]

The structure of iron-containing [[hemoglobin. The protein subunits are in red and blue, and the iron-containing heme groups in green. From .]]

含铁[[血红蛋白]]的结构。蛋白质亚基为红色和蓝色，含铁血红素基为绿色。

===Mineral and cofactors===
矿物质和辅因子

{{further||Bioinorganic chemistry}}

Inorganic elements play critical roles in metabolism; some are abundant (e.g. [[sodium]] and [[potassium]]) while others function at minute concentrations. About 99% of a human's body weight is made up of the elements [[carbon]], [[nitrogen]], [[calcium]], [[sodium]], [[chlorine]], [[potassium]], [[hydrogen]], [[phosphorus]], [[oxygen]] and [[sulfur]]. [[Organic compound]]s (proteins, lipids and carbohydrates) contain the majority of the carbon and nitrogen; most of the oxygen and hydrogen is present as water.

Inorganic elements play critical roles in metabolism; some are abundant (e.g. sodium and potassium) while others function at minute concentrations. About 99% of a human's body weight is made up of the elements carbon, nitrogen, calcium, sodium, chlorine, potassium, hydrogen, phosphorus, oxygen and sulfur. Organic compounds (proteins, lipids and carbohydrates) contain the majority of the carbon and nitrogen; most of the oxygen and hydrogen is present as water<ref name="Heymsfield">{{cite journal | vauthors = Heymsfield SB, Waki M, Kehayias J, Lichtman S, Dilmanian FA, Kamen Y, Wang J, Pierson RN | display-authors = 6 | title = Chemical and elemental analysis of humans in vivo using improved body composition models | journal = The American Journal of Physiology | volume = 261 | issue = 2 Pt 1 | pages = E190-8 | date = August 1991 | pmid = 1872381 | doi = 10.1152/ajpendo.1991.261.2.E190 }}</ref>.

无机元素在新陈代谢中起着关键作用; 有些元素含量丰富(例如:钠和钾) ，而另一些元素则在微量浓度下发挥作用。人的体重约99%是由碳、氮、钙、钠、氯、钾、氢、磷、氧和硫等元素组成。有机化合物（蛋白质、脂类和碳水化合物）含有大部分的碳和氮；大部分的氧和氢以水的形式存在。

The abundant inorganic elements act as [[electrolyte]]s. The most important ions are [[sodium]], [[potassium]], [[calcium]], [[magnesium]], [[chloride]], [[phosphate]] and the organic ion [[bicarbonate]]. The maintenance of precise [[ion gradient]]s across [[cell membrane]]s maintains [[osmotic pressure]] and [[pH]]. Ions are also critical for [[nerve]] and [[muscle]] function, as [[action potential]]s in these tissues are produced by the exchange of electrolytes between the [[extracellular fluid]] and the cell's fluid, the [[cytosol]]. Electrolytes enter and leave cells through proteins in the cell membrane called [[ion channel]]s. For example, [[muscle contraction]] depends upon the movement of calcium, sodium and potassium through ion channels in the cell membrane and [[T-tubule]]s.

The abundant inorganic elements act as electrolytes. The most important ions are sodium, potassium, calcium, magnesium, chloride, phosphate and the organic ion bicarbonate. The maintenance of precise ion gradients across cell membranes maintains osmotic pressure and pH. Ions are also critical for nerve and muscle function, as action potentials in these tissues are produced by the exchange of electrolytes between the extracellular fluid and the cell's fluid, the cytosol. Electrolytes enter and leave cells through proteins in the cell membrane called ion channels. For example, muscle contraction depends upon the movement of calcium, sodium and potassium through ion channels in the cell membrane and T-tubules.

丰富的无机元用作电解质。最重要的离子是钠、钾、钙、镁、氯化物、磷酸盐和有机离子重碳酸盐。维持细胞膜上精确的离子梯度可以维持[[渗透压]]和 ph 值。离子对于神经和肌肉功能也是至关重要的<ref>{{cite book |date=| chapter = Electrolyte Balance | chapter-url=https://opentextbc.ca/anatomyandphysiology/chapter/26-3-electrolyte-balance/ | title = Anatomy and Physiology | publisher = OpenStax |access-date=23 June 2020 }}</ref>，因为这些组织中的动作电位是由细胞外液和细胞液之间的电解质交换产生的。电解质通过细胞膜上称为离子通道的蛋白质进入和离开细胞<ref>{{cite book |last1=Lodish |first1=Harvey |last2=Berk |first2=Arnold |last3=Zipursky |first3=S. Lawrence |last4=Matsudaira |first4=Paul |last5=Baltimore |first5=David |last6=Darnell |first6=James | name-list-style = vanc |date=2000| chapter =The Action Potential and Conduction of Electric Impulses|chapter-url= https://www.ncbi.nlm.nih.gov/books/NBK21668/ |title =Molecular Cell Biology | edition = 4th |language=en|via=NCBI}}</ref> 。例如，肌肉收缩依赖于钙、钠和钾通过细胞膜和T管道中的离子通道的运动<ref>{{cite journal | vauthors = Dulhunty AF | title = Excitation-contraction coupling from the 1950s into the new millennium | journal = Clinical and Experimental Pharmacology & Physiology | volume = 33 | issue = 9 | pages = 763–72 | date = September 2006 | pmid = 16922804 | doi = 10.1111/j.1440-1681.2006.04441.x | s2cid = 37462321 }}</ref>。

[[Transition metal]]s are usually present as [[trace element]]s in organisms, with [[zinc]] and [[iron]] being most abundant of those. These metals are used in some proteins as [[Cofactor (biochemistry)|cofactors]] and are essential for the activity of enzymes such as [[catalase]] and oxygen-carrier proteins such as [[hemoglobin]]. Metal cofactors are bound tightly to specific sites in proteins; although enzyme cofactors can be modified during catalysis, they always return to their original state by the end of the reaction catalyzed. Metal micronutrients are taken up into organisms by specific transporters and bind to storage proteins such as [[ferritin]] or [[metallothionein]] when not in use.

Transition metals are usually present as trace elements in organisms, with zinc and iron being most abundant of those. These metals are used in some proteins as cofactors and are essential for the activity of enzymes such as catalase and oxygen-carrier proteins such as hemoglobin. Metal cofactors are bound tightly to specific sites in proteins; although enzyme cofactors can be modified during catalysis, they always return to their original state by the end of the reaction catalyzed. Metal micronutrients are taken up into organisms by specific transporters and bind to storage proteins such as ferritin or metallothionein when not in use.

过渡金属通常以微量元素的形式存在于生物体内，其中锌和铁最为丰富<ref>{{cite book| vauthors = Torres-Romero JC, Alvarez-Sánchez ME, Fernández-Martín K, Alvarez-Sánchez LC, Arana-Argáez V, Ramírez-Camacho M, Lara-Riegos J | chapter=Zinc Efflux in Trichomonas vaginalis: In Silico Identification and Expression Analysis of CDF-Like Genes|date=2018| title =Quantitative Models for Microscopic to Macroscopic Biological Macromolecules and Tissues|pages=149–168| veditors = Olivares-Quiroz L, Resendis-Antonio O |place=Cham|publisher=Springer International Publishing|language=en|doi=10.1007/978-3-319-73975-5_8|isbn=978-3-319-73975-5 }}</ref>。这些金属元素在某些蛋白质中作为辅因子，是催化酶等酶和血红蛋白等氧载体蛋白活性所必需的金属辅因子。<ref>{{cite book|last=Craig Will|first=Leonard Ashley | name-list-style = vanc |title=Manufacturing Engineering & Technology|publisher=Scientific e-Resources|year=2019|isbn=9781839472428|location=Waltham Abbey|pages=190–196}}</ref>金属辅因子与蛋白质中的特定位点紧密结合，虽然在催化过程中酶的辅因子可以被改变，但在催化反应结束时，它们总是恢复到原来的状态。金属微量营养素由特定的转运体带入生物体内，不用时与储存蛋白如铁蛋白或金属硫蛋白结合<ref>{{cite journal | vauthors = Cousins RJ, Liuzzi JP, Lichten LA | title = Mammalian zinc transport, trafficking, and signals | journal = The Journal of Biological Chemistry | volume = 281 | issue = 34 | pages = 24085–9 | date = August 2006 | pmid = 16793761 | doi = 10.1074/jbc.R600011200 | url = https://www.jbc.org/content/281/34/24085 | doi-access = free }}</ref><ref>{{cite journal | vauthors = Dunn LL, Suryo Rahmanto Y, Richardson DR | title = Iron uptake and metabolism in the new millennium | journal = Trends in Cell Biology | volume = 17 | issue = 2 | pages = 93–100 | date = February 2007 | pmid = 17194590 | doi = 10.1016/j.tcb.2006.12.003 }}</ref>。

==Catabolism==
分解代谢

[[Catabolism]] is the set of metabolic processes that break down large molecules. These include breaking down and oxidizing food molecules. The purpose of the catabolic reactions is to provide the energy and components needed by anabolic reactions which build molecules. The exact nature of these catabolic reactions differ from organism to organism, and organisms can be classified based on their sources of energy and carbon (their [[primary nutritional groups]]), as shown in the table below. Organic molecules are used as a source of energy by [[organotroph]]s, while [[lithotroph]]s use inorganic substrates, and [[phototroph]]s capture sunlight as [[Potential energy#Chemical potential energy|chemical energy]].However, all these different forms of metabolism depend on [[redox]] reactions that involve the transfer of electrons from reduced donor molecules such as [[organic molecule]]s, water, [[ammonia]], [[hydrogen sulfide]] or [[Ferrous|ferrous ions]] to acceptor molecules such as [[oxygen]], [[nitrate]] or [[sulfate]]. In animals, these reactions involve complex [[organic molecule]]s that are broken down to simpler molecules, such as [[carbon dioxide]] and water. In [[photosynthesis|photosynthetic]] organisms, such as plants and [[cyanobacteria]], these electron-transfer reactions do not release energy but are used as a way of storing energy absorbed from sunlight.

Catabolism is the set of metabolic processes that break down large molecules. These include breaking down and oxidizing food molecules. The purpose of the catabolic reactions is to provide the energy and components needed by anabolic reactions which build molecules. The exact nature of these catabolic reactions differ from organism to organism, and organisms can be classified based on their sources of energy and carbon (their primary nutritional groups), as shown in the table below. Organic molecules are used as a source of energy by organotrophs, while lithotrophs use inorganic substrates, and phototrophs capture sunlight as chemical energy. However, all these different forms of metabolism depend on redox reactions that involve the transfer of electrons from reduced donor molecules such as organic molecules, water, ammonia, hydrogen sulfide or ferrous ions to acceptor molecules such as oxygen, nitrate or sulfate. In animals, these reactions involve complex organic molecules that are broken down to simpler molecules, such as carbon dioxide and water. In photosynthetic organisms, such as plants and cyanobacteria, these electron-transfer reactions do not release energy but are used as a way of storing energy absorbed from sunlight.

分解代谢是指分解大分子的一系列代谢过程。其中包括分解和氧化食物分子。分解代谢反应的目的是为构建分子的合成代谢反应提供所需的能量和成分。这些分解代谢反应的确切性质因生物体而异<ref name="Alberts 2002">{{cite book |last1=Alberts|first1=Bruce|last2=Johnson|first2=Alexander|last3=Lewis|first3=Julian|last4=Raff|first4=Martin|last5=Roberts|first5=Keith|last6=Walter|first6=Peter| name-list-style = vanc |date=2002|chapter =How Cells Obtain Energy from Food|url=https://www.ncbi.nlm.nih.gov/books/NBK26882/|title =Molecular Biology of the Cell | edition = 4th |language=en|via=NCBI}}</ref>，生物体可以根据它们的能量和碳的来源（其主要营养组）进行分类，如下表所示。有机养生物把有机分子作为能量来源，而岩养生物利用无机基质，光养生物利用阳光（获得化学能）<ref>{{cite journal|last=Raven|first=Ja| name-list-style = vanc |date=2009-09-03|title=Contributions of anoxygenic and oxygenic phototrophy and chemolithotrophy to carbon and oxygen fluxes in aquatic environments|url=http://www.int-res.com/abstracts/ame/v56/n2-3/p177-192/|journal=Aquatic Microbial Ecology|language=en|volume=56|pages=177–192|doi=10.3354/ame01315|issn=0948-3055|doi-access=free}}</ref> 。然而，所有这些不同形式的新陈代谢都依赖于氧化还原反应，这些反应涉及电子从还原的供体分子（如有机分子，水，氨，硫化氢或亚铁离子）转移到受体分子（如氧，硝酸盐或硫酸盐）。在动物中，这些反应涉及复杂的有机分子，它们被分解成更简单的分子，如二氧化碳和水。在诸如植物和蓝藻这样的光合生物体中，这些电子转移反应不释放能量，而是用来储存从阳光中吸收的能量<ref name=Nelson2004>{{cite journal | vauthors = Nelson N, Ben-Shem A | title = The complex architecture of oxygenic photosynthesis | journal = Nature Reviews. Molecular Cell Biology | volume = 5 | issue = 12 | pages = 971–82 | date = December 2004 | pmid = 15573135 | doi = 10.1038/nrm1525 | s2cid = 5686066 }}</ref>。

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{ | class = “ wikitable float-right” style = “ text-align: center; width: 50% ; ”

|+Classification of organisms based on their metabolism <ref>{{cite book| vauthors = Madigan MT, Martinko JM |title=Brock Mikrobiologie|date=2006|publisher=Pearson Studium|isbn=3-8273-7187-2|edition=11., überarb. Aufl|location=München|pages=604, 621|oclc=162303067}}</ref>

|+Classification of organisms based on their metabolism

| + 根据其新陈代谢对生物进行分类

|-

|-

|-

| rowspan="2" style="background:#ff0;"|Energy source || style="background:#ff0;"| sunlight || style="background:#ff0;"| photo- || rowspan=2 colspan=2 |   || rowspan="6" style="background:#7fc31c;"| -troph

| rowspan="2" style="background:#ff0;"|Energy source || style="background:#ff0;"| sunlight || style="background:#ff0;"| photo- || rowspan=2 colspan=2 |   || rowspan="6" style="background:#7fc31c;"| -troph

能量源
|- style="background:#ff0;"

|- style="background:#ff0;"

|| Preformed molecules || style="background:#ff0;"| chemo-

|| Preformed molecules || style="background:#ff0;"| chemo-

预制分子 | | | | style = ”背景: # ff0; ” | 化疗-

|-

|-

| rowspan="2" style="background:#ffb300;"| Electron donor || style="background:#ffb300;"| [[organic compound]] || rowspan=2 |   || style="background:#ffb300;"| organo- || rowspan=2 |  

| rowspan="2" style="background:#ffb300;"| Electron donor || style="background:#ffb300;"| organic compound || rowspan=2 |   || style="background:#ffb300;"| organo- || rowspan=2 |  

有机化合物 | rowspan = 2 | | | style = ”背景: # ffb300; ” | organic compound = 2 | | | style = ”背景: # ffb300; ” | organo-| rowspan = 2 |

|- style="background:#ffb300;"

|- style="background:#ffb300;"

|-style = ”背景: # ffb300; ”

|| [[inorganic compound]] || style="background:#ffb300;"| litho-

|| inorganic compound || style="background:#ffb300;"| litho-

无机化合物: # ffb300

|-

|-

|-

| rowspan="2" style="background:#fb805f;"| Carbon source || style="background:#fb805f;"| [[organic compound]] || rowspan=2 colspan=2 |   || style="background:#fb805f;"| hetero-

| rowspan="2" style="background:#fb805f;"| Carbon source || style="background:#fb805f;"| organic compound || rowspan=2 colspan=2 |   || style="background:#fb805f;"| hetero-

2 | | rowspan = 2 | | | style = “ background: # fb805f; ” | Carbon source | style = “ background: # fb805f; ” | organic compound | rowspan = 2 colspan = 2 | | | | style = “ background: # fb805f; ” | hetero-
碳源
|- style="background:#fb805f;"

|- style="background:#fb805f;"

|-style = “ background: # fb805f; ”

|| [[inorganic compound]] || style="background:#fb805f;"| auto-

|| inorganic compound || style="background:#fb805f;"| auto-

无机化合物: fb805f

|}

|}

|}

The most common set of catabolic reactions in animals can be separated into three main stages. In the first stage, large organic molecules, such as [[protein]]s, [[polysaccharide]]s or [[lipid]]s, are digested into their smaller components outside cells. Next, these smaller molecules are taken up by cells and converted to smaller molecules, usually [[acetyl-CoA|acetyl coenzyme A]] (acetyl-CoA), which releases some energy. Finally, the acetyl group on the CoA is oxidised to water and carbon dioxide in the [[citric acid cycle]] and [[electron transport chain]], releasing the energy that is stored by reducing the coenzyme [[nicotinamide adenine dinucleotide]] (NAD+) into NADH.

The most common set of catabolic reactions in animals can be separated into three main stages. In the first stage, large organic molecules, such as proteins, polysaccharides or lipids, are digested into their smaller components outside cells. Next, these smaller molecules are taken up by cells and converted to smaller molecules, usually acetyl coenzyme A (acetyl-CoA), which releases some energy. Finally, the acetyl group on the CoA is oxidised to water and carbon dioxide in the citric acid cycle and electron transport chain, releasing the energy that is stored by reducing the coenzyme nicotinamide adenine dinucleotide (NAD+) into NADH.

动物中最常见的分解代谢反应可以分为三个主要阶段。在第一阶段，大的有机分子，如蛋白质，多糖或脂类，在细胞外被消化成较小的分子。接下来，这些较小的分子被细胞吸收并转化成更小的分子，通常是乙酰辅酶A (acetyl-CoA) ，并释放出一些能量。最后，辅酶 A 上的乙酰基在三羧酸循环和电子传递链中被氧化成水和二氧化碳，释放出储存的能量，将辅酶烟酰胺腺嘌呤二核苷酸（NAD+）还原成NADH<ref name="Alberts 2002"/>。

===Digestion===
消化

{{further|Digestion|Gastrointestinal tract}}

更多信息：消化和胃肠道

Macromolecules cannot be directly processed by cells. Macromolecules must be broken into smaller units before they can be used in cell metabolism. Different classes of enzymes were being used to digest these polymers. These [[digestive enzyme]]s include [[protease]]s that digest proteins into amino acids, as well as [[glycoside hydrolase]]s that digest polysaccharides into simple sugars known as [[monosaccharides]].

Macromolecules cannot be directly processed by cells. Macromolecules must be broken into smaller units before they can be used in cell metabolism. Different classes of enzymes were being used to digest these polymers. These digestive enzymes include proteases that digest proteins into amino acids, as well as glycoside hydrolases that digest polysaccharides into simple sugars known as monosaccharides.

大分子不能直接被细胞处理。大分子必须先被分解成较小的单位，才能用于细胞代谢。不同类别的酶被用来消化这些聚合物。这些消化酶包括将蛋白质消化成氨基酸的蛋白酶，以及将多糖消化成单糖的糖苷水解酶<ref>{{cite book|last=Demirel, Yaşar|title=Energy : production, conversion, storage, conservation, and coupling|publisher=Springer|year=2016|isbn=978-3-319-29650-0|edition=Second|location=Lincoln|pages=431|oclc=945435943}}</ref>。

Microbes simply secrete digestive enzymes into their surroundings, while animals only secrete these enzymes from specialized cells in their [[Gastrointestinal tract|guts]], including the [[stomach]] and [[pancreas]], and [[salivary gland]]s. The amino acids or sugars released by these extracellular enzymes are then pumped into cells by [[active transport]] proteins.

Microbes simply secrete digestive enzymes into their surroundings, while animals only secrete these enzymes from specialized cells in their guts, including the stomach and pancreas, and salivary glands. The amino acids or sugars released by these extracellular enzymes are then pumped into cells by active transport proteins.

微生物简单直接地将消化酶分泌到周围环境中<ref>{{cite journal | vauthors = Häse CC, Finkelstein RA | title = Bacterial extracellular zinc-containing metalloproteases | journal = Microbiological Reviews | volume = 57 | issue = 4 | pages = 823–37 | date = December 1993 | pmid = 8302217 | pmc = 372940 | doi = 10.1128/MMBR.57.4.823-837.1993 }}</ref><ref>{{cite journal | vauthors = Gupta R, Gupta N, Rathi P | title = Bacterial lipases: an overview of production, purification and biochemical properties | journal = Applied Microbiology and Biotechnology | volume = 64 | issue = 6 | pages = 763–81 | date = June 2004 | pmid = 14966663 | doi = 10.1007/s00253-004-1568-8 | s2cid = 206934353 }}</ref>，而动物必须通过它们肠道(包括胃、胰腺和唾液腺)中的特定细胞分泌这些酶。<ref>{{cite journal | vauthors = Hoyle T | title = The digestive system: linking theory and practice | journal = British Journal of Nursing | volume = 6 | issue = 22 | pages = 1285–91 | year = 1997 | pmid = 9470654 | doi = 10.12968/bjon.1997.6.22.1285 }}</ref>这些细胞外酶释放的氨基酸或糖通过活性转运蛋白被泵入细胞内<ref>{{cite journal | vauthors = Souba WW, Pacitti AJ | title = How amino acids get into cells: mechanisms, models, menus, and mediators | journal = JPEN. Journal of Parenteral and Enteral Nutrition | volume = 16 | issue = 6 | pages = 569–78 | year = 1992 | pmid = 1494216 | doi = 10.1177/0148607192016006569 }}</ref><ref>{{cite journal | vauthors = Barrett MP, Walmsley AR, Gould GW | title = Structure and function of facilitative sugar transporters | journal = Current Opinion in Cell Biology | volume = 11 | issue = 4 | pages = 496–502 | date = August 1999 | pmid = 10449337 | doi = 10.1016/S0955-0674(99)80072-6 }}</ref>。

[[File:Catabolism schematic.svg|thumb|left|upright=1.35|[[蛋白质]]，[[碳水化合物]]和[[脂肪]]分解代谢的简化概述 ]]

===Energy from organic compounds===
有机化合物的能量

{{further|Cellular respiration|Fermentation (biochemistry)|Carbohydrate catabolism|Fat catabolism|Protein catabolism}}

更多信息：细胞呼吸，发酵（生物化学），碳水化合物分解代谢，脂肪分解代谢和蛋白质分解代谢

Carbohydrate catabolism is the breakdown of carbohydrates into smaller units. Carbohydrates are usually taken into cells once they have been digested into [[monosaccharide]]s. Once inside, the major route of breakdown is [[glycolysis]], where sugars such as [[glucose]] and [[fructose]] are converted into [[pyruvic acid|pyruvate]] and some ATP is generated. Pyruvate is an intermediate in several metabolic pathways, but the majority is converted to [[acetyl-CoA]] through aerobic (with oxygen) glycolysis and fed into the [[citric acid cycle]]. Although some more ATP is generated in the citric acid cycle, the most important product is NADH, which is made from NAD+ as the acetyl-CoA is oxidized. This oxidation releases [[carbon dioxide]] as a waste product. In anaerobic conditions, glycolysis produces [[lactic acid|lactate]], through the enzyme [[lactate dehydrogenase]] re-oxidizing NADH to NAD+ for re-use in glycolysis. An alternative route for glucose breakdown is the [[pentose phosphate pathway]], which reduces the coenzyme [[NADPH]] and produces [[pentose]] sugars such as [[ribose]], the sugar component of [[nucleic acid]]s.

Carbohydrate catabolism is the breakdown of carbohydrates into smaller units. Carbohydrates are usually taken into cells once they have been digested into monosaccharides. Once inside, the major route of breakdown is glycolysis, where sugars such as glucose and fructose are converted into pyruvate and some ATP is generated. Pyruvate is an intermediate in several metabolic pathways, but the majority is converted to acetyl-CoA through aerobic (with oxygen) glycolysis and fed into the citric acid cycle. Although some more ATP is generated in the citric acid cycle, the most important product is NADH, which is made from NAD+ as the acetyl-CoA is oxidized. This oxidation releases carbon dioxide as a waste product. In anaerobic conditions, glycolysis produces lactate, through the enzyme lactate dehydrogenase re-oxidizing NADH to NAD+ for re-use in glycolysis. An alternative route for glucose breakdown is the pentose phosphate pathway, which reduces the coenzyme NADPH and produces pentose sugars such as ribose, the sugar component of nucleic acids.

碳水化合物分解代谢是将碳水化合物分解成较小的单位的过程。碳水化合物一旦被消化成单糖，通常就被带入细胞。一旦进入细胞内<ref>{{cite journal | vauthors = Bell GI, Burant CF, Takeda J, Gould GW | title = Structure and function of mammalian facilitative sugar transporters | journal = The Journal of Biological Chemistry | volume = 268 | issue = 26 | pages = 19161–4 | date = September 1993 | pmid = 8366068 }}</ref>，分解的主要途径就是糖酵解，其中糖（例如葡萄糖和果糖）被转化为丙酮酸并生成一些ATP。<ref name=Bouche>{{cite journal | vauthors = Bouché C, Serdy S, Kahn CR, Goldfine AB | title = The cellular fate of glucose and its relevance in type 2 diabetes | journal = Endocrine Reviews | volume = 25 | issue = 5 | pages = 807–30 | date = October 2004 | pmid = 15466941 | doi = 10.1210/er.2003-0026 | df = dmy-all | doi-access = free }}</ref>丙酮酸是几种代谢途径中的中间体，但大多数通过有氧（含氧）糖酵解转化为乙酰辅酶A并进入三羧酸循环。尽管在三羧酸循环中会产生更多的ATP，但最重要的产物是NADH，它是由 NAD + 在乙酰辅酶A被氧化后制成的。这种氧化释放出作为废物的二氧化碳。在厌氧条件下，糖酵解产生乳酸盐，即由乳酸脱氢酶将丙酮酸盐转化为乳酸盐，同时将NADH重新氧化为NAD + 再用于糖酵解。<ref>{{cite journal | vauthors = Alfarouk KO, Verduzco D, Rauch C, Muddathir AK, Adil HH, Elhassan GO, Ibrahim ME, David Polo Orozco J, Cardone RA, Reshkin SJ, Harguindey S | display-authors = 6 | title = Glycolysis, tumor metabolism, cancer growth and dissemination. A new pH-based etiopathogenic perspective and therapeutic approach to an old cancer question | journal = Oncoscience | volume = 1 | issue = 12 | pages = 777–802 | date = 18 December 2014 | pmid = 25621294 | pmc = 4303887 | doi = 10.18632/oncoscience.109 | doi-access = free }}</ref>葡萄糖分解的另一种途径是磷酸戊糖途径，它还原辅酶NADPH并产生戊糖，如核糖（核酸的糖成分）。

Fats are catabolised by [[hydrolysis]] to free fatty acids and glycerol. The glycerol enters glycolysis and the fatty acids are broken down by [[beta oxidation]] to release acetyl-CoA, which then is fed into the citric acid cycle. Fatty acids release more energy upon oxidation than carbohydrates because carbohydrates contain more oxygen in their structures. Steroids are also broken down by some bacteria in a process similar to beta oxidation, and this breakdown process involves the release of significant amounts of acetyl-CoA, propionyl-CoA, and pyruvate, which can all be used by the cell for energy. ''M. tuberculosis'' can also grow on the lipid [[cholesterol]] as a sole source of carbon, and genes involved in the cholesterol use pathway(s) have been validated as important during various stages of the infection lifecycle of ''M. tuberculosis''.

Fats are catabolised by hydrolysis to free fatty acids and glycerol. The glycerol enters glycolysis and the fatty acids are broken down by beta oxidation to release acetyl-CoA, which then is fed into the citric acid cycle. Fatty acids release more energy upon oxidation than carbohydrates because carbohydrates contain more oxygen in their structures. Steroids are also broken down by some bacteria in a process similar to beta oxidation, and this breakdown process involves the release of significant amounts of acetyl-CoA, propionyl-CoA, and pyruvate, which can all be used by the cell for energy. M. tuberculosis can also grow on the lipid cholesterol as a sole source of carbon, and genes involved in the cholesterol use pathway(s) have been validated as important during various stages of the infection lifecycle of M. tuberculosis.

脂肪通过水解作用分解为游离脂肪酸和甘油。甘油进入糖酵解，脂肪酸被 β氧化分解，释放出乙酰辅酶A，然后进入三羧酸循环。脂肪酸在氧化时会释放比碳水化合物更多的能量，因为碳水化合物的结构中含有更多的氧。类固醇也会被一些细菌在类似于 β 氧化的过程中分解，这个分解过程会释放出大量的乙酰辅酶A、丙酰辅酶A和丙酮酸，它们都可以给细胞提供能量。结核杆菌也可以依靠脂质胆固醇这唯一的碳源生长，而且参与胆固醇利用途径的基因已经被证实在结核杆菌感染生命周期的不同阶段都是重要的<ref>{{cite journal | vauthors = Wipperman MF, Sampson NS, Thomas ST | title = Pathogen roid rage: cholesterol utilization by Mycobacterium tuberculosis | journal = Critical Reviews in Biochemistry and Molecular Biology | volume = 49 | issue = 4 | pages = 269–93 | date = 2014 | pmid = 24611808 | pmc = 4255906 | doi = 10.3109/10409238.2014.895700 }}</ref>。

[[Amino acid]]s are either used to synthesize proteins and other biomolecules, or oxidized to [[urea]] and carbon dioxide as a source of energy. The oxidation pathway starts with the removal of the amino group by a [[transaminase]]. The amino group is fed into the [[urea cycle]], leaving a deaminated carbon skeleton in the form of a [[keto acid]]. Several of these keto acids are intermediates in the citric acid cycle, for example the deamination of [[glutamate]] forms α-[[alpha-Ketoglutaric acid|ketoglutarate]]. The [[glucogenic amino acid]]s can also be converted into glucose, through [[gluconeogenesis]] (discussed below).

Amino acids are either used to synthesize proteins and other biomolecules, or oxidized to urea and carbon dioxide as a source of energy. The oxidation pathway starts with the removal of the amino group by a transaminase. The amino group is fed into the urea cycle, leaving a deaminated carbon skeleton in the form of a keto acid. Several of these keto acids are intermediates in the citric acid cycle, for example the deamination of glutamate forms α-ketoglutarate. The glucogenic amino acids can also be converted into glucose, through gluconeogenesis (discussed below).

氨基酸可以用来合成蛋白质和其他生物分子，也可以被氧化成尿素和二氧化碳从而提供能量<ref>{{cite journal | vauthors = Sakami W, Harrington H | title = Amino Acid Metabolism | journal = Annual Review of Biochemistry | volume = 32 | issue = | pages = 355–98 | year = 1963 | pmid = 14144484 | doi = 10.1146/annurev.bi.32.070163.002035 }}</ref>。氧化途径从转氨酶去除氨基酸上的氨基开始。氨基进入尿素循环，留下酮酸形式的脱氨基碳骨架。其中一些酮酸是三羧酸循环的中间产物，例如谷氨酸的脱氨反应形成 α- 酮戊二酸<ref>{{cite journal | vauthors = Brosnan JT | title = Glutamate, at the interface between amino acid and carbohydrate metabolism | journal = The Journal of Nutrition | volume = 130 | issue = 4S Suppl | pages = 988S–90S | date = April 2000 | pmid = 10736367 | doi = 10.1093/jn/130.4.988S | doi-access = free }}</ref>。葡萄糖原氨基酸也可以通过糖异生作用转化为葡萄糖(具体内容见下文)<ref>{{cite journal | vauthors = Young VR, Ajami AM | title = Glutamine: the emperor or his clothes? | journal = The Journal of Nutrition | volume = 131 | issue = 9 Suppl | pages = 2449S–59S; discussion 2486S–7S | date = September 2001 | pmid = 11533293 | doi = 10.1093/jn/131.9.2449S | doi-access = free }}</ref>。

==Energy transformations==
能量转换

===Oxidative phosphorylation===
氧化磷酸化

{{further|Oxidative phosphorylation|Chemiosmosis|Mitochondrion}}

更多信息：氧化磷酸化，化学渗透和线粒体

In oxidative phosphorylation, the electrons removed from organic molecules in areas such as the protagon acid cycle are transferred to oxygen and the energy released is used to make ATP. This is done in [[eukaryote]]s by a series of proteins in the membranes of mitochondria called the [[electron transport chain]]. In [[prokaryote]]s, these proteins are found in the cell's [[bacterial cell structure|inner membrane]]. These proteins use the energy released from passing electrons from [[reducing agent|reduced]] molecules like NADH onto [[oxygen]] to pump [[proton]]s across a membrane.

In oxidative phosphorylation, the electrons removed from organic molecules in areas such as the protagon acid cycle are transferred to oxygen and the energy released is used to make ATP. This is done in eukaryotes by a series of proteins in the membranes of mitochondria called the electron transport chain. In prokaryotes, these proteins are found in the cell's inner membrane. These proteins use the energy released from passing electrons from reduced molecules like NADH onto oxygen to pump protons across a membrane.

氧化磷酸化中，通过如柠檬酸循环等代谢途径，电子从被消化吸收的食物分子上转移到氧气上，并将产生的能量以ATP的方式储存起来。在真核生物中，这一过程是通过线粒体膜上的一系列膜蛋白来完成的，被称为电子传递链。而在原核生物中，这些蛋白质存在于细胞的内膜中。<ref>{{cite journal | vauthors = Hosler JP, Ferguson-Miller S, Mills DA | title = Energy transduction: proton transfer through the respiratory complexes | journal = Annual Review of Biochemistry | volume = 75 | issue = | pages = 165–87 | year = 2006 | pmid = 16756489 | pmc = 2659341 | doi = 10.1146/annurev.biochem.75.062003.101730 }}</ref>这些蛋白质利用电子从还原性分子(如NADH)传递到氧气所释放的能量来泵送质子穿过细胞膜<ref>{{cite journal | vauthors = Schultz BE, Chan SI | title = Structures and proton-pumping strategies of mitochondrial respiratory enzymes | journal = Annual Review of Biophysics and Biomolecular Structure | volume = 30 | issue = | pages = 23–65 | year = 2001 | pmid = 11340051 | doi = 10.1146/annurev.biophys.30.1.23 | url = https://authors.library.caltech.edu/1623/1/SCHarbbs01.pdf }}</ref>。

[[File:ATPsyn.gif|thumb|right|[[ATP合成酶]]的作用机制。ATP 显示为红色，ADP 和磷酸显示为粉红色，转柄亚基显示为黑色]]

Pumping protons out of the mitochondria creates a proton [[diffusion|concentration difference]] across the membrane and generates an [[electrochemical gradient]]. This force drives protons back into the mitochondrion through the base of an enzyme called [[ATP synthase]]. The flow of protons makes the stalk subunit rotate, causing the [[active site]] of the synthase domain to change shape and phosphorylate [[adenosine diphosphate]] – turning it into ATP.

Pumping protons out of the mitochondria creates a proton concentration difference across the membrane and generates an electrochemical gradient. This force drives protons back into the mitochondrion through the base of an enzyme called ATP synthase. The flow of protons makes the stalk subunit rotate, causing the active site of the synthase domain to change shape and phosphorylate adenosine diphosphate– turning it into ATP.

将质子泵出线粒体，会在膜上形成质子浓度差，产生电化学梯度。<ref>{{cite journal | vauthors = Capaldi RA, Aggeler R | title = Mechanism of the F(1)F(0)-type ATP synthase, a biological rotary motor | journal = Trends in Biochemical Sciences | volume = 27 | issue = 3 | pages = 154–60 | date = March 2002 | pmid = 11893513 | doi = 10.1016/S0968-0004(01)02051-5 }}</ref>这种力量促使质子通过ATP合成酶的基座回到线粒体中。质子的流动使柄亚基旋转，从而改变合成酶域的活性位点的形状，使二磷酸腺苷磷酸化--变成ATP<ref name=Dimroth/>。

===Energy from inorganic compounds===
无机化合物的能量

{{further|Microbial metabolism|Nitrogen cycle}}

更多信息：微生物代谢和氮循环

[[Chemolithotroph]]y is a type of metabolism found in [[prokaryote]]s where energy is obtained from the oxidation of [[inorganic compound]]s. These organisms can use [[hydrogen]], reduced [[sulfur]] compounds (such as [[sulfide]], [[hydrogen sulfide]] and [[thiosulfate]]),<ref name=Physiology1/> [[Iron(II) oxide|ferrous iron (FeII)]] or [[ammonia]] as sources of reducing power and they gain energy from the oxidation of these compounds with electron acceptors such as [[oxygen]] or [[nitrite]]. These microbial processes are important in global [[biogeochemical cycle]]s such as [[acetogenesis]], [[nitrification]] and [[denitrification]] and are critical for [[fertility (soil)|soil fertility]].

Chemolithotrophy is a type of metabolism found in prokaryotes where energy is obtained from the oxidation of inorganic compounds. These organisms can use hydrogen, reduced sulfur compounds (such as sulfide, hydrogen sulfide and thiosulfate), or ammonia as sources of reducing power and they gain energy from the oxidation of these compounds with electron acceptors such as oxygen or nitrite. These microbial processes are important in global biogeochemical cycles such as acetogenesis, nitrification and denitrification and are critical for soil fertility.

化能无机营养是在原核生物中发现的一种新陈代谢，其能量来自于无机化合物的氧化。这些生物可以利用氢气、<ref>{{cite journal | vauthors = Friedrich B, Schwartz E | title = Molecular biology of hydrogen utilization in aerobic chemolithotrophs | journal = Annual Review of Microbiology | volume = 47 | issue = | pages = 351–83 | year = 1993 | pmid = 8257102 | doi = 10.1146/annurev.mi.47.100193.002031 }}</ref> 还原硫化合物(如硫化物、硫化氢和硫代硫酸酯<ref>{{cite journal | vauthors = Weber KA, Achenbach LA, Coates JD | title = Microorganisms pumping iron: anaerobic microbial iron oxidation and reduction | journal = Nature Reviews. Microbiology | volume = 4 | issue = 10 | pages = 752–64 | date = October 2006 | pmid = 16980937 | doi = 10.1038/nrmicro1490 | url = https://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=1203&context=bioscifacpub | s2cid = 8528196 }}</ref>)或氨<ref>{{cite journal | vauthors = Jetten MS, Strous M, van de Pas-Schoonen KT, Schalk J, van Dongen UG, van de Graaf AA, Logemann S, Muyzer G, van Loosdrecht MC, Kuenen JG | display-authors = 6 | title = The anaerobic oxidation of ammonium | journal = FEMS Microbiology Reviews | volume = 22 | issue = 5 | pages = 421–37 | date = December 1998 | pmid = 9990725 | doi = 10.1111/j.1574-6976.1998.tb00379.x | doi-access = free }}</ref>作为还原力的来源，它们从这些化合物与氧或亚硝酸盐等电子接受体的氧化作用中获得能量。这些微生物过程<ref>{{cite journal | vauthors = Simon J | title = Enzymology and bioenergetics of respiratory nitrite ammonification | journal = FEMS Microbiology Reviews | volume = 26 | issue = 3 | pages = 285–309 | date = August 2002 | pmid = 12165429 | doi = 10.1111/j.1574-6976.2002.tb00616.x | doi-access = free }}</ref>在全球生物地球化学循环（如乙酰化、硝化和反硝化）中非常重要，对土壤肥力也很关键<ref>{{cite journal | vauthors = Conrad R | title = Soil microorganisms as controllers of atmospheric trace gases (H2, CO, CH4, OCS, N2O, and NO) | journal = Microbiological Reviews | volume = 60 | issue = 4 | pages = 609–40 | date = December 1996 | pmid = 8987358 | pmc = 239458 | doi = 10.1128/MMBR.60.4.609-640.1996 }}</ref><ref>{{cite journal | vauthors = Barea JM, Pozo MJ, Azcón R, Azcón-Aguilar C | title = Microbial co-operation in the rhizosphere | journal = Journal of Experimental Botany | volume = 56 | issue = 417 | pages = 1761–78 | date = July 2005 | pmid = 15911555 | doi = 10.1093/jxb/eri197 | doi-access = free }}</ref>。

===Energy from light===
光能
{{further|Phototroph|Photophosphorylation|Chloroplast}}

更多信息：光养，光磷酸化和叶绿体

The energy in sunlight is captured by [[plant]]s, [[cyanobacteria]], [[purple bacteria]], [[green sulfur bacteria]] and some [[protist]]s. This process is often coupled to the conversion of carbon dioxide into organic compounds, as part of photosynthesis, which is discussed below. The energy capture and carbon fixation systems can however operate separately in prokaryotes, as purple bacteria and green sulfur bacteria can use sunlight as a source of energy, while switching between carbon fixation and the fermentation of organic compounds.

The energy in sunlight is captured by plants, cyanobacteria, purple bacteria, green sulfur bacteria and some protists. This process is often coupled to the conversion of carbon dioxide into organic compounds, as part of photosynthesis, which is discussed below. The energy capture and carbon fixation systems can however operate separately in prokaryotes, as purple bacteria and green sulfur bacteria can use sunlight as a source of energy, while switching between carbon fixation and the fermentation of organic compounds.

阳光中的能量被植物、蓝藻、紫细菌、绿硫细菌和一些原生生物所吸收。这个过程通常与二氧化碳转化为有机化合物相结合，这是光合作用的一部分，下文将对此进行讨论。然而，原核生物的能量捕获和碳固定系统可以单独运作，因为紫色细菌和绿硫细菌可以利用阳光作为能源，同时在碳固定和有机化合物发酵之间转换<ref>{{cite journal | vauthors = van der Meer MT, Schouten S, Bateson MM, Nübel U, Wieland A, Kühl M, de Leeuw JW, Sinninghe Damsté JS, Ward DM | display-authors = 6 | title = Diel variations in carbon metabolism by green nonsulfur-like bacteria in alkaline siliceous hot spring microbial mats from Yellowstone National Park | journal = Applied and Environmental Microbiology | volume = 71 | issue = 7 | pages = 3978–86 | date = July 2005 | pmid = 16000812 | pmc = 1168979 | doi = 10.1128/AEM.71.7.3978-3986.2005 }}</ref><ref>{{cite journal | vauthors = Tichi MA, Tabita FR | title = Interactive control of Rhodobacter capsulatus redox-balancing systems during phototrophic metabolism | journal = Journal of Bacteriology | volume = 183 | issue = 21 | pages = 6344–54 | date = November 2001 | pmid = 11591679 | pmc = 100130 | doi = 10.1128/JB.183.21.6344-6354.2001 }}</ref>。

In many organisms, the capture of solar energy is similar in principle to oxidative phosphorylation, as it involves the storage of energy as a proton concentration gradient. This proton motive force then drives ATP synthesis. The electrons needed to drive this electron transport chain come from light-gathering proteins called [[photosynthetic reaction centre]]s. Reaction centers are classed into two types depending on the nature of [[photosynthetic pigment]] present, with most photosynthetic bacteria only having one type, while plants and cyanobacteria have two.

In many organisms, the capture of solar energy is similar in principle to oxidative phosphorylation, as it involves the storage of energy as a proton concentration gradient. This proton motive force then drives ATP synthesis. The electrons needed to drive this electron transport chain come from light-gathering proteins called photosynthetic reaction centres. Reaction centers are classed into two types depending on the nature of photosynthetic pigment present, with most photosynthetic bacteria only having one type, while plants and cyanobacteria have two.

在许多生物体中，太阳能的获取在原理上类似于氧化磷酸化，因为它涉及到以质子浓度梯度的形式储存能量。这种质子动力驱动 ATP 的合成<ref>{{cite book |last1=Alberts|first1=Bruce|last2=Johnson|first2=Alexander|last3=Lewis|first3=Julian|last4=Raff|first4=Martin|last5=Roberts|first5=Keith|last6=Walter|first6=Peter | name-list-style = vanc |date=2002|chapter =Energy Conversion: Mitochondria and Chloroplasts|url=https://www.ncbi.nlm.nih.gov/books/NBK21063/|title =Molecular Biology of the Cell. 4th edition|language=en}}</ref> 。驱动这种电子传递链所需的电子来自于聚光蛋白质，这种蛋白质被叫做光合反应中心。根据存在的光合色素的性质，反应中心分为两种类型。大多数光合细菌只有一种类型，而植物和蓝藻有两种类型<ref>{{cite journal | vauthors = Allen JP, Williams JC | title = Photosynthetic reaction centers | journal = FEBS Letters | volume = 438 | issue = 1–2 | pages = 5–9 | date = October 1998 | pmid = 9821949 | doi = 10.1016/S0014-5793(98)01245-9 | s2cid = 21596537 }}</ref>。

In plants, algae, and cyanobacteria, [[photosystem|photosystem II]] uses light energy to remove electrons from water, releasing oxygen as a waste product. The electrons then flow to the [[cytochrome b6f complex]], which uses their energy to pump protons across the [[thylakoid]] membrane in the [[chloroplast]]. These protons move back through the membrane as they drive the ATP synthase, as before. The electrons then flow through [[photosystem|photosystem I]] and can then either be used to reduce the coenzyme NADP+.f. These cooenzyme can be used in the [[Calvin cycle]], which is discussed below, or recycled for further ATP generation.

In plants, algae, and cyanobacteria, photosystem II uses light energy to remove electrons from water, releasing oxygen as a waste product. The electrons then flow to the cytochrome b6f complex, which uses their energy to pump protons across the thylakoid membrane in the chloroplast. These protons move back through the membrane as they drive the ATP synthase, as before. The electrons then flow through photosystem I and can then either be used to reduce the coenzyme NADP + .fThese cooenzyme can be used in the Calvin cycle, which is discussed below, or recycled for further ATP generation.

在植物、藻类和蓝藻中，光系统 II 利用光能将电子从水中移走，释放出氧气。然后电子流向细胞色素b6f蛋白复合体，后者利用它们的能量穿过叶绿体中的类囊体膜，泵入质子<ref name=Nelson2004/>。这些质子在驱动ATP合成酶时通过膜向后移动，就像之前一样。然后电子流经光系统I，可以用来减少辅酶NADP + <ref>{{cite journal | vauthors = Munekage Y, Hashimoto M, Miyake C, Tomizawa K, Endo T, Tasaka M, Shikanai T | title = Cyclic electron flow around photosystem I is essential for photosynthesis | journal = Nature | volume = 429 | issue = 6991 | pages = 579–82 | date = June 2004 | pmid = 15175756 | doi = 10.1038/nature02598 | bibcode = 2004Natur.429..579M | s2cid = 4421776 }}</ref>。这些辅酶可用于[[卡尔文循环]](下文将对此进行讨论)，或被循环用于进一步生成ATP。

==Anabolism==
合成代谢

{{further|Anabolism}}

更多信息：合成代谢

'''Anabolism''' is the set of constructive metabolic processes where the energy released by catabolism is used to synthesize complex molecules. In general, the complex molecules that make up cellular structures are constructed step-by-step from small and simple precursors. Anabolism involves three basic stages. First, the production of precursors such as [[amino acid]]s, [[monosaccharide]]s, [[Terpenoid|isoprenoids]] and [[nucleotide]]s, secondly, their activation into reactive forms using energy from ATP, and thirdly, the assembly of these precursors into complex molecules such as [[protein]]s, [[polysaccharide]]s, [[lipid]]s and [[nucleic acid]]s.

Anabolism is the set of constructive metabolic processes where the energy released by catabolism is used to synthesize complex molecules. In general, the complex molecules that make up cellular structures are constructed step-by-step from small and simple precursors. Anabolism involves three basic stages. First, the production of precursors such as amino acids, monosaccharides, isoprenoids and nucleotides, secondly, their activation into reactive forms using energy from ATP, and thirdly, the assembly of these precursors into complex molecules such as proteins, polysaccharides, lipids and nucleic acids.

合成代谢是一系列建设性的新陈代谢过程，在这一系列过程中分解代谢所释放的能量被用来合成复杂的分子。一般来说，组成细胞结构的复杂分子是由小而简单的前体逐步构成的。合成代谢包括三个基本阶段。首先是氨基酸、单糖、异戊二烯和核苷酸等前体的产生，其次是利用ATP产生的能量将它们活化成活性形式，第三是将这些前体组装成复杂的分子，如蛋白质、多糖、脂质和核酸<ref name=":0">{{cite web|last=Mandal|first=Ananya| name-list-style = vanc |date=2009-11-26|title=What is Anabolism?|url=https://www.news-medical.net/life-sciences/What-is-Anabolism.aspx|access-date=2020-07-04|website=News-Medical.net|language=en}}</ref>。

Anabolism in organisms can be different according to the source of constructed molecules in their cells. [[Autotroph]]s such as plants can construct the complex organic molecules in cells such as polysaccharides and proteins from simple molecules like [[carbon dioxide]] and water. [[Heterotroph]]s, on the other hand, require a source of more complex substances, such as monosaccharides and amino acids, to produce these complex molecules. Organisms can be further classified by ultimate source of their energy: photoautotrophs and photoheterotrophs obtain energy from light, whereas chemoautotrophs and chemoheterotrophs obtain energy from inorganic oxidation reactions.

Anabolism in organisms can be different according to the source of constructed molecules in their cells. Autotrophs such as plants can construct the complex organic molecules in cells such as polysaccharides and proteins from simple molecules like carbon dioxide and water. Heterotrophs, on the other hand, require a source of more complex substances, such as monosaccharides and amino acids, to produce these complex molecules. Organisms can be further classified by ultimate source of their energy: photoautotrophs and photoheterotrophs obtain energy from light, whereas chemoautotrophs and chemoheterotrophs obtain energy from inorganic oxidation reactions.

生物体的合成代谢根据其细胞中构建分子的来源而有所不同。植物等自养生物可以在细胞中利用二氧化碳和水等简单分子中构建复杂的有机分子（如多糖和蛋白质）。而异养生物则需要更复杂的物质来源（如单糖和氨基酸）才能产生这些复杂的分子。生物可以根据其能量的最终来源进一步分类: 光自养生物和光异养生物从光中获得能量，而化能自养生物和化能异养生物从无机氧化反应中获得能量<ref name=":0" />
。

===Carbon fixation===
碳固定
{{further|Photosynthesis|Carbon fixation|Chemosynthesis}}

更多信息：光合作用，碳固定和化学合成

[[File:Plagiomnium affine laminazellen.jpeg|thumb|含叶绿体（绿色）的植物细胞（以紫色壁为边界），叶绿体是光合作用的部位]]

Photosynthesis is the synthesis of carbohydrates from sunlight and [[carbon dioxide]] (CO2). In plants, cyanobacteria and algae, oxygenic photosynthesis splits water, with oxygen produced as a waste product. This process uses the ATP and NADPH produced by the [[photosynthetic reaction centre]]s, as described above, to convert CO2 into [[glycerate 3-phosphate]], which can then be converted into glucose. This carbon-fixation reaction is carried out by the enzyme [[RuBisCO]] as part of the [[Calvin cycle|Calvin – Benson cycle]]. Three types of photosynthesis occur in plants, [[C3 carbon fixation]], [[C4 carbon fixation]] and [[Crassulacean acid metabolism|CAM photosynthesis]]. These differ by the route that carbon dioxide takes to the Calvin cycle, with C3 plants fixing CO2 directly, while C4 and CAM photosynthesis incorporate the CO2 into other compounds first, as adaptations to deal with intense sunlight and dry conditions.

Photosynthesis is the synthesis of carbohydrates from sunlight and carbon dioxide (CO2). In plants, cyanobacteria and algae, oxygenic photosynthesis splits water, with oxygen produced as a waste product. This process uses the ATP and NADPH produced by the photosynthetic reaction centres, as described above, to convert CO2 into glycerate 3-phosphate, which can then be converted into glucose. This carbon-fixation reaction is carried out by the enzyme RuBisCO as part of the Calvin – Benson cycle.[64] Three types of photosynthesis occur in plants, C3 carbon fixation, C4 carbon fixation and CAM photosynthesis. These differ by the route that carbon dioxide takes to the Calvin cycle, with C3 plants fixing CO2 directly, while C4 and CAM photosynthesis incorporate the CO2 into other compounds first, as adaptations to deal with intense sunlight and dry conditions.

光合作用就是依靠阳光和二氧化碳(CO2)合成碳水化合物。在植物中，蓝细菌和藻类的含氧光合作用使水分解，排出氧气。如前所述，这一过程利用光合反应中心产生的ATP和NADPH将CO2转化为三磷酸甘油酯，然后再转化为葡萄糖。这个固碳反应作为卡尔文-本森Calvin – Benson 循环的一部分是在RuBisCO酶的催化下进行的<ref>{{cite journal | vauthors = Miziorko HM, Lorimer GH | title = Ribulose-1,5-bisphosphate carboxylase-oxygenase | journal = Annual Review of Biochemistry | volume = 52 | issue = | pages = 507–35 | year = 1983 | pmid = 6351728 | doi = 10.1146/annurev.bi.52.070183.002451 }}</ref>。植物有三种类型的光合作用:C3固碳、C4固碳和CAM光合作用。它们的不同之处在于二氧化碳进入卡尔文循环的路径不同，C3植物直接固定二氧化碳，而C4和CAM植物首先将二氧化碳吸收到其他化合物中，以适应强烈的阳光和干燥的环境<ref>{{cite journal | vauthors = Dodd AN, Borland AM, Haslam RP, Griffiths H, Maxwell K | title = Crassulacean acid metabolism: plastic, fantastic | journal = Journal of Experimental Botany | volume = 53 | issue = 369 | pages = 569–80 | date = April 2002 | pmid = 11886877 | doi = 10.1093/jexbot/53.369.569 | doi-access = free }}</ref>。

In photosynthetic [[prokaryote]]s the mechanisms of carbon fixation are more diverse. Here, carbon dioxide can be fixed by the Calvin – Benson cycle, a [[Reverse Krebs cycle|reversed citric acid]] cycle, or the carboxylation of acetyl-CoA. Prokaryotic [[Chemotroph|chemoautotrophs]] also fix CO2 through the Calvin–Benson cycle, but use energy from inorganic compounds to drive the reaction.

In photosynthetic prokaryotes the mechanisms of carbon fixation are more diverse. Here, carbon dioxide can be fixed by the Calvin– Benson cycle, a reversed citric acid cycle, or the carboxylation of acetyl-CoA. Prokaryotic chemoautotrophs also fix CO2 through the Calvin–Benson cycle, but use energy from inorganic compounds to drive the reaction.

在能够光合作用的原核生物中，碳固定的机制更加多样。对它们而言，二氧化碳可以通过Calvin– Benson循环、反向三羧酸循环<ref>{{cite journal | vauthors = Hügler M, Wirsen CO, Fuchs G, Taylor CD, Sievert SM | title = Evidence for autotrophic CO2 fixation via the reductive tricarboxylic acid cycle by members of the epsilon subdivision of proteobacteria | journal = Journal of Bacteriology | volume = 187 | issue = 9 | pages = 3020–7 | date = May 2005 | pmid = 15838028 | pmc = 1082812 | doi = 10.1128/JB.187.9.3020-3027.2005 }}</ref>或乙酰辅酶A的羧化作用得到固定。原核化能自养生物也通过Calvin– Benson环固定CO 2 <ref>{{cite journal | vauthors = Strauss G, Fuchs G | title = Enzymes of a novel autotrophic CO2 fixation pathway in the phototrophic bacterium Chloroflexus aurantiacus, the 3-hydroxypropionate cycle | journal = European Journal of Biochemistry | volume = 215 | issue = 3 | pages = 633–43 | date = August 1993 | pmid = 8354269 | doi = 10.1111/j.1432-1033.1993.tb18074.x }}</ref><ref>{{cite journal | vauthors = Wood HG | title = Life with CO or CO2 and H2 as a source of carbon and energy | journal = FASEB Journal | volume = 5 | issue = 2 | pages = 156–63 | date = February 1991 | pmid = 1900793 | doi = 10.1096/fasebj.5.2.1900793 | s2cid = 45967404 }}</ref>，但它们利用无机化合物的能量来驱动反应<ref>{{cite journal | vauthors = Shively JM, van Keulen G, Meijer WG | title = Something from almost nothing: carbon dioxide fixation in chemoautotrophs | journal = Annual Review of Microbiology | volume = 52 | issue = | pages = 191–230 | year = 1998 | pmid = 9891798 | doi = 10.1146/annurev.micro.52.1.191 }}</ref>。

===Carbohydrates and glycans===
碳水化合物和聚糖
{{further|Gluconeogenesis|Glyoxylate cycle|Glycogenesis|Glycosylation}}

更多信息：糖异生，乙醛酸循环，糖异生和糖基化

In carbohydrate anabolism, simple organic acids can be converted into [[monosaccharide]]s such as [[glucose]] and then used to assemble [[polysaccharide]]s such as [[starch]]. The generation of [[glucose]] from compounds like [[pyruvate]], [[lactic acid|lactate]], [[glycerol]], [[glycerate 3-phosphate]] and [[amino acid]]s is called [[gluconeogenesis]]. Gluconeogenesis converts pyruvate to [[glucose-6-phosphate]] through a series of intermediates, many of which are shared with [[glycolysis]]. However, this pathway is not simply [[glycolysis]] run in reverse, as several steps are catalyzed by non-glycolytic enzymes. This is important as it allows the formation and breakdown of glucose to be regulated separately, and prevents both pathways from running simultaneously in a [[futile cycle]].

In carbohydrate anabolism, simple organic acids can be converted into monosaccharides such as glucose and then used to assemble polysaccharides such as starch. The generation of glucose from compounds like pyruvate, lactate, glycerol, glycerate 3-phosphate and amino acids is called gluconeogenesis. Gluconeogenesis converts pyruvate to glucose-6-phosphate through a series of intermediates, many of which are shared with glycolysis.However, this pathway is not simply glycolysis run in reverse, as several steps are catalyzed by non-glycolytic enzymes. This is important as it allows the formation and breakdown of glucose to be regulated separately, and prevents both pathways from running simultaneously in a futile cycle.

在碳水化合物合成代谢过程中，简单的有机酸可转化为葡萄糖等单糖，再用于合成淀粉等多糖。由丙酮酸、乳酸、甘油、3-磷酸甘油酸和氨基酸等化合物生成葡萄糖称为葡萄糖异生。糖异生作用通过一系列中间产物将丙酮酸转化为葡萄糖-6-磷酸，其中许多中间产物与糖酵解过程相同<ref name=Bouche/>。然而，这一途径并不是简单的糖酵解逆向运行，因为有几个步骤是由非糖酵解酶催化的。这很重要，因为它使得葡萄糖的形成和分解可以分别被调节，而且防止了两条途径在无效循环中同时运行<ref>{{cite journal | vauthors = Boiteux A, Hess B | title = Design of glycolysis | journal = Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences | volume = 293 | issue = 1063 | pages = 5–22 | date = June 1981 | pmid = 6115423 | doi = 10.1098/rstb.1981.0056 | doi-access = free | bibcode = 1981RSPTB.293....5B }}</ref><ref>{{cite journal | vauthors = Pilkis SJ, el-Maghrabi MR, Claus TH | title = Fructose-2,6-bisphosphate in control of hepatic gluconeogenesis. From metabolites to molecular genetics | journal = Diabetes Care | volume = 13 | issue = 6 | pages = 582–99 | date = June 1990 | pmid = 2162755 | doi = 10.2337/diacare.13.6.582 | s2cid = 44741368 }}</ref>。

Although fat is a common way of storing energy, in [[vertebrate]]s such as humans the [[fatty acid]]s in these stores cannot be converted to glucose through [[gluconeogenesis]] as these organisms cannot convert acetyl-CoA into [[pyruvate]]; plants do, but animals do not, have the necessary enzymatic machinery. As a result, after long-term starvation, vertebrates need to produce [[Ketone body|ketone bodies]] from fatty acids to replace glucose in tissues such as the brain that cannot metabolize fatty acids.In other organisms such as plants and bacteria, this metabolic problem is solved using the [[glyoxylate cycle]], which bypasses the [[decarboxylation]] step in the citric acid cycle and allows the transformation of acetyl-CoA to [[oxaloacetate]], where it can be used for the production of glucose. Other than fat, glucose is stored in most tissues, as an energy resource available within the tissue through glycogenesis which was usually being used to maintained glucose level in blood.

Although fat is a common way of storing energy, in vertebrates such as humans the fatty acids in these stores cannot be converted to glucose through gluconeogenesis as these organisms cannot convert acetyl-CoA into pyruvate; plants do, but animals do not, have the necessary enzymatic machinery. As a result, after long-term starvation, vertebrates need to produce ketone bodies from fatty acids to replace glucose in tissues such as the brain that cannot metabolize fatty acids. In other organisms such as plants and bacteria, this metabolic problem is solved using the glyoxylate cycle, which bypasses the decarboxylation step in the citric acid cycle and allows the transformation of acetyl-CoA to oxaloacetate, where it can be used for the production of glucose. Other than fat, glucose is stored in most tissues, as an energy resource available within the tissue through glycogenesis which was usually being used to maintained glucose level in blood.

虽然脂肪是储存能量的一种常见方式，但在脊椎动物(如人类)体内储存的脂肪酸不能通过葡萄糖异生作用转化为葡萄糖，因为这些生物不能将乙酰辅酶A转化为丙酮酸;植物有必要的酶催化机制，而动物没有<ref name=Ensign>{{cite journal | vauthors = Ensign SA | title = Revisiting the glyoxylate cycle: alternate pathways for microbial acetate assimilation | journal = Molecular Microbiology | volume = 61 | issue = 2 | pages = 274–6 | date = July 2006 | pmid = 16856935 | doi = 10.1111/j.1365-2958.2006.05247.x | s2cid = 39986630 }}</ref>。因此，在长期饥饿后，脊椎动物需要从脂肪酸中产生酮体，以取代大脑等不能代谢脂肪酸的组织中的葡萄糖。在其他生物体如植物和细菌中，这个代谢问题是靠乙醛酸循环来解决的<ref>{{cite journal | vauthors = Finn PF, Dice JF | title = Proteolytic and lipolytic responses to starvation | journal = Nutrition | volume = 22 | issue = 7–8 | pages = 830–44 | year = 2006 | pmid = 16815497 | doi = 10.1016/j.nut.2006.04.008 }}</ref> 。乙醛酸循环绕过三羧酸循环中的脱羧步骤，并将乙酰辅酶a转化为草酰乙酸，在那里它可以用来生产葡萄糖。除了脂肪<ref name=Ensign/><ref name=Kornberg>{{cite journal | vauthors = Kornberg HL, Krebs HA | title = Synthesis of cell constituents from C2-units by a modified tricarboxylic acid cycle | journal = Nature | volume = 179 | issue = 4568 | pages = 988–91 | date = May 1957 | pmid = 13430766 | doi = 10.1038/179988a0 | s2cid = 40858130 | bibcode = 1957Natur.179..988K }}</ref>，葡萄糖也作为一种能量资源储存在大多数组织中，一般会通过它的糖化来维持血液中的葡萄糖水平<ref>{{cite journal|last1=Evans|first1=Rhys D.|last2=Heather|first2=Lisa C. | name-list-style = vanc |date=June 2016|title=Metabolic pathways and abnormalities|journal=Surgery (Oxford)|volume=34|issue=6|pages=266–272|doi=10.1016/j.mpsur.2016.03.010|issn=0263-9319|url=https://ora.ox.ac.uk/objects/uuid:84c0a8e7-38e9-4de2-ba19-9f129a07987a}}</ref> 。

Polysaccharides and [[glycan]]s are made by the sequential addition of monosaccharides by [[glycosyltransferase]] from a reactive sugar-phosphate donor such as [[uridine diphosphate glucose]] (UDP-Glc) to an acceptor [[hydroxyl]] group on the growing polysaccharide. As any of the [[hydroxyl]] groups on the ring of the substrate can be acceptors, the polysaccharides produced can have straight or branched structures. The polysaccharides produced can have structural or metabolic functions themselves, or be transferred to lipids and proteins by enzymes called [[oligosaccharyltransferase]]s.

Polysaccharides and glycans are made by the sequential addition of monosaccharides by glycosyltransferase from a reactive sugar-phosphate donor such as uridine diphosphate glucose (UDP-Glc) to an acceptor hydroxyl group on the growing polysaccharide. As any of the hydroxyl groups on the ring of the substrate can be acceptors, the polysaccharides produced can have straight or branched structures. The polysaccharides produced can have structural or metabolic functions themselves, or be transferred to lipids and proteins by enzymes called oligosaccharyltransferases.

多糖和聚糖是在糖基转移酶作用下，将单糖从活性糖-磷酸盐供体（如尿苷二磷酸葡萄糖(UDP-Glc)）依次加入到生长中的多糖的受体羟基上形成的。由于底物环上的任何羟基都可以作为受体，所以产生的多糖会有直链或支链结构<ref>{{cite book |last1=Freeze|first1=Hudson H. | name-list-style = vanc | chapter =Glycosylation Precursors|date=2015|url=http://www.ncbi.nlm.nih.gov/books/NBK453043/| title = Essentials of Glycobiology|editor-last=Varki|editor-first=Ajit|edition=3rd|place=Cold Spring Harbor (NY)|publisher=Cold Spring Harbor Laboratory Press|pmid=28876856|access-date=2020-07-08|last2=Hart|first2=Gerald W.|last3=Schnaar|first3=Ronald L.|doi=10.1101/glycobiology.3e.005 |doi-broken-date=1 November 2020 |editor2-last=Cummings|editor2-first=Richard D.|editor3-last=Esko|editor3-first=Jeffrey D.|editor4-last=Stanley|editor4-first=Pamela }}</ref>。产生的多糖本身具有结构或代谢功能，还可以通过低聚糖转移酶转移到脂质和蛋白质中<ref>{{cite journal | vauthors = Opdenakker G, Rudd PM, Ponting CP, Dwek RA | title = Concepts and principles of glycobiology | journal = FASEB Journal | volume = 7 | issue = 14 | pages = 1330–7 | date = November 1993 | pmid = 8224606 | doi = 10.1096/fasebj.7.14.8224606 | s2cid = 10388991 }}</ref><ref>{{cite journal | vauthors = McConville MJ, Menon AK | title = Recent developments in the cell biology and biochemistry of glycosylphosphatidylinositol lipids (review) | journal = Molecular Membrane Biology | volume = 17 | issue = 1 | pages = 1–16 | year = 2000 | pmid = 10824734 | doi = 10.1080/096876800294443 | doi-access = free }}</ref>。

===Fatty acids, isoprenoids and sterol===

脂肪酸，类异戊二烯和固醇

{{further|Fatty acid synthesis|Steroid metabolism}}

更多信息：脂肪酸合成和类固醇代谢

[[File:Sterol synthesis.svg|thumb|right|upright=1.6|具有中间体[[异戊烯基焦磷酸酯]]（IPP），[[二甲基烯丙基焦磷酸酯]]（DMAPP），[[香叶基焦磷酸酯]]（GPP）和[[角鲨烯的类固醇]]合成途径的简化版本。为了清晰起见，省略了一些中间步骤。]]

Fatty acids are made by [[fatty acid synthase]]s that polymerize and then reduce acetyl-CoA units. The acyl chains in the fatty acids are extended by a cycle of reactions that add the acyl group, reduce it to an alcohol, [[dehydration reaction|dehydrate]] it to an [[alkene]] group and then reduce it again to an [[alkane]] group. The enzymes of fatty acid biosynthesis are divided into two groups: in animals and fungi, all these fatty acid synthase reactions are carried out by a single multifunctional type I protein, while in plant [[plastid]]s and bacteria separate type II enzymes perform each step in the pathway.

Fatty acids are made by fatty acid synthases that polymerize and then reduce acetyl-CoA units. The acyl chains in the fatty acids are extended by a cycle of reactions that add the acyl group, reduce it to an alcohol, dehydrate it to an alkene group and then reduce it again to an alkane group. The enzymes of fatty acid biosynthesis are divided into two groups: in animals and fungi, all these fatty acid synthase reactions are carried out by a single multifunctional type I protein, while in plant plastids and bacteria separate type II enzymes perform each step in the pathway.

脂肪酸是由脂肪酸合成酶聚合并还原乙酰辅酶A单元制成的。脂肪酸中的酰基链通过一些反应的循环得以延伸，这些反应包括:添加酰基，将其还原为醇，脱水成烯烃基团，然后再还原为烷烃基团。脂肪酸生物合成的酶可以分为两类：在动物和真菌中，所有脂肪酸合成酶的反应都是由单一的多功能I型蛋白来完成的<ref>{{cite journal | vauthors = Chirala SS, Wakil SJ | title = Structure and function of animal fatty acid synthase | journal = Lipids | volume = 39 | issue = 11 | pages = 1045–53 | date = November 2004 | pmid = 15726818 | doi = 10.1007/s11745-004-1329-9 | s2cid = 4043407 }}</ref>，而在植物的质体和细菌中，则由单独的II型酶来完成每一步<ref>{{cite journal | vauthors = White SW, Zheng J, Zhang YM | title = The structural biology of type II fatty acid biosynthesis | journal = Annual Review of Biochemistry | volume = 74 | issue = | pages = 791–831 | year = 2005 | pmid = 15952903 | doi = 10.1146/annurev.biochem.74.082803.133524 }}</ref><ref>{{cite journal | vauthors = Ohlrogge JB, Jaworski JG | title = Regulation of Fatty Acid Synthesis | journal = Annual Review of Plant Physiology and Plant Molecular Biology | volume = 48 | issue = | pages = 109–136 | date = June 1997 | pmid = 15012259 | doi = 10.1146/annurev.arplant.48.1.109 | s2cid = 46348092 }}</ref>。

[[Terpene]]s and [[terpenoid|isoprenoids]] are a large class of lipids that include the [[carotenoid]]s and form the largest class of plant [[natural product]]s. These compounds are made by the assembly and modification of [[isoprene]] units donated from the reactive precursors [[isopentenyl pyrophosphate]] and [[dimethylallyl pyrophosphate]]. These precursors can be made in different ways. In animals and archaea, the [[mevalonate pathway]] produces these compounds from acetyl-CoA, while in plants and bacteria the [[non-mevalonate pathway]] uses pyruvate and [[glyceraldehyde 3-phosphate]] as substrates. One important reaction that uses these activated isoprene donors is [[steroid biosynthesis|sterol biosynthesis]]. Here, the isoprene units are joined together to make [[squalene]] and then folded up and formed into a set of rings to make [[lanosterol]]. Lanosterol can then be converted into other sterol such as [[cholesterol]] and [[ergosterol]].

Terpenes and isoprenoids are a large class of lipids that include the carotenoids and form the largest class of plant natural products. These compounds are made by the assembly and modification of isoprene units donated from the reactive precursors isopentenyl pyrophosphate and dimethylallyl pyrophosphate. These precursors can be made in different ways. In animals and archaea, the mevalonate pathway produces these compounds from acetyl-CoA, while in plants and bacteria the non-mevalonate pathway uses pyruvate and glyceraldehyde 3-phosphate as substrates. One important reaction that uses these activated isoprene donors is sterol biosynthesis. Here, the isoprene units are joined together to make squalene and then folded up and formed into a set of rings to make lanosterol. Lanosterol can then be converted into other sterol such as cholesterol and ergosterol.

萜烯和异戊二烯是一大类脂类，包括类胡萝卜素，也是最大的一类植物天然产品<ref>{{cite journal | vauthors = Dubey VS, Bhalla R, Luthra R | title = An overview of the non-mevalonate pathway for terpenoid biosynthesis in plants | journal = Journal of Biosciences | volume = 28 | issue = 5 | pages = 637–46 | date = September 2003 | pmid = 14517367 | doi = 10.1007/BF02703339 | url = http://www.ias.ac.in/jbiosci/sep2003/637.pdf | url-status = dead | s2cid = 27523830 | archive-url = https://web.archive.org/web/20070415213325/http://www.ias.ac.in/jbiosci/sep2003/637.pdf | df = | archive-date = 15 April 2007 }}</ref>。这些化合物是由反应性前体焦磷酸异戊烯酯和焦磷酸二甲基烯丙基酯所提供的异戊二烯单元组装和改性而成。这些前体可以靠不同的途径制造<ref name=Kuzuyama>{{cite journal | vauthors = Kuzuyama T, Seto H | title = Diversity of the biosynthesis of the isoprene units | journal = Natural Product Reports | volume = 20 | issue = 2 | pages = 171–83 | date = April 2003 | pmid = 12735695 | doi = 10.1039/b109860h }}</ref>。在动物和古生物中，甲戊二酸途径从乙酰辅酶A产生这些化合物<ref>{{cite journal | vauthors = Grochowski LL, Xu H, White RH | title = Methanocaldococcus jannaschii uses a modified mevalonate pathway for biosynthesis of isopentenyl diphosphate | journal = Journal of Bacteriology | volume = 188 | issue = 9 | pages = 3192–8 | date = May 2006 | pmid = 16621811 | pmc = 1447442 | doi = 10.1128/JB.188.9.3192-3198.2006 }}</ref>，而在植物和细菌中，非甲戊二酸途径使用丙酮酸和甘油醛3-磷酸作为底物。使用这些活化的异戊二烯供体的一个重要反应是固醇的生物合成<ref name=Kuzuyama/><ref>{{cite journal | vauthors = Lichtenthaler HK | title = The 1-Deoxy-D-Xylulose-5-Phosphate Pathway of Isoprenoid Biosynthesis in Plants | journal = Annual Review of Plant Physiology and Plant Molecular Biology | volume = 50 | issue = | pages = 47–65 | date = June 1999 | pmid = 15012203 | doi = 10.1146/annurev.arplant.50.1.47 }}</ref>。在该反应中，异戊二烯单元连接在一起，制成角鲨烯，然后折叠起来形成一组环，制成羊毛固醇<ref name=Schroepfer>{{cite journal | vauthors = Schroepfer GJ | title = Sterol biosynthesis | journal = Annual Review of Biochemistry | volume = 50 | issue = | pages = 585–621 | year = 1981 | pmid = 7023367 | doi = 10.1146/annurev.bi.50.070181.003101 }}</ref>。羊毛固醇随后可转化为其他固醇，如胆固醇和麦角固醇<ref name=Schroepfer/><ref>{{cite journal | vauthors = Lees ND, Skaggs B, Kirsch DR, Bard M | title = Cloning of the late genes in the ergosterol biosynthetic pathway of Saccharomyces cerevisiae--a review | journal = Lipids | volume = 30 | issue = 3 | pages = 221–6 | date = March 1995 | pmid = 7791529 | doi = 10.1007/BF02537824 | s2cid = 4019443 }}</ref>。

===Proteins===
蛋白质类
{{further|Protein biosynthesis|Amino acid synthesis}}

更多信息：蛋白质生物合成和氨基酸合成

Organisms vary in their ability to synthesize the 20 common amino acids. Most bacteria and plants can synthesize all twenty, but mammals can only synthesize eleven nonessential amino acids, so nine [[essential amino acid]]s must be obtained from food. Some simple [[parasite]]s, such as the bacteria ''[[Mycoplasma pneumoniae]]'', lack all amino acid synthesis and take their amino acids directly from their hosts. All amino acids are synthesized from intermediates in glycolysis, the citric acid cycle, or the pentose phosphate pathway. Nitrogen is provided by [[glutamate]] and [[glutamine]]. Nonessensial amino acid synthesis depends on the formation of the appropriate alpha-keto acid, which is then [[Transaminase|transaminated]] to form an amino acid.

Organisms vary in their ability to synthesize the 20 common amino acids. Most bacteria and plants can synthesize all twenty, but mammals can only synthesize eleven nonessential amino acids, so nine essential amino acids must be obtained from food. All amino acids are synthesized from intermediates in glycolysis, the citric acid cycle, or the pentose phosphate pathway. Nitrogen is provided by glutamate and glutamine. Nonessensial amino acid synthesis depends on the formation of the appropriate alpha-keto acid, which is then transaminated to form an amino acid.

生物体合成这20种常见氨基酸的能力各不相同。大多数细菌和植物都能合成这20种氨基酸，但哺乳动物只能合成11种非必需氨基酸，因此必须从食物中获得9种必需氨基酸<ref name=Nelson/>。所有的氨基酸都是由糖酵解、三羧酸循环或磷酸戊糖途径的中间产物合成的<ref>{{cite journal | vauthors = Himmelreich R, Hilbert H, Plagens H, Pirkl E, Li BC, Herrmann R | title = Complete sequence analysis of the genome of the bacterium Mycoplasma pneumoniae | journal = Nucleic Acids Research | volume = 24 | issue = 22 | pages = 4420–49 | date = November 1996 | pmid = 8948633 | pmc = 146264 | doi = 10.1093/nar/24.22.4420 }}</ref>。氮由谷氨酸和谷氨酰胺提供。非关键氨基酸的合成取决于适当的α-酮酸的形成，它可以转氨基形成氨基酸<ref>{{cite book |last1 = Guyton |first1 = Arthur C. | first2 = John E. | last2 = Hall | name-list-style = vanc |title=Textbook of Medical Physiology |url=https://archive.org/details/textbookmedicalp00acgu |url-access=limited |publisher=Elsevier |year=2006 |location=Philadelphia |pages=[https://archive.org/details/textbookmedicalp00acgu/page/n889 855]–6 |isbn=978-0-7216-0240-0}}</ref>。

Amino acids are made into proteins by being joined together in a chain of [[peptide bond]]s. Each different protein has a unique sequence of amino acid residues: this is its [[primary structure]]. Just as the letters of the alphabet can be combined to form an almost endless variety of words, amino acids can be linked in varying sequences to form a huge variety of proteins. Proteins are made from amino acids that have been activated by attachment to a [[transfer RNA]] molecule through an [[ester]] bond. This [[aminoacyl-tRNA]] precursor is produced in an [[Adenosine triphosphate|ATP]]-dependent reaction carried out by an [[aminoacyl tRNA synthetase]] This aminoacyl-tRNA is then a substrate for the [[ribosome]], which joins the amino acid onto the elongating protein chain, using the sequence information in a [[messenger RNA]].

Amino acids are made into proteins by being joined together in a chain of peptide bonds. Each different protein has a unique sequence of amino acid residues: this is its primary structure. Just as the letters of the alphabet can be combined to form an almost endless variety of words, amino acids can be linked in varying sequences to form a huge variety of proteins. Proteins are made from amino acids that have been activated by attachment to a transfer RNA molecule through an ester bond. This aminoacyl-tRNA precursor is produced in an ATP-dependent reaction carried out by an aminoacyl tRNA synthetase. This aminoacyl-tRNA is then a substrate for the ribosome, which joins the amino acid onto the elongating protein chain, using the sequence information in a messenger RNA.

氨基酸通过肽键链连接成蛋白质。每种不同的蛋白质都有一个独特的氨基酸残基序列：这就是它的主要结构。就像字母表的字母可以组合成无穷无尽的各种单词一样，氨基酸也能以不同的序列连接起来，形成种类繁多的蛋白质。蛋白质是由氨基酸制成的，这些氨基酸通过酯键附着在转运RNA(tRNA)分子上而被激活。氨基酰tRNA前体是在靠氨基酰tRNA合成酶进行的ATP依赖性反应中产生的.<ref>{{cite journal | vauthors = Ibba M, Söll D | title = The renaissance of aminoacyl-tRNA synthesis | journal = EMBO Reports | volume = 2 | issue = 5 | pages = 382–7 | date = May 2001 | pmid = 11375928 | pmc = 1083889 | doi = 10.1093/embo-reports/kve095 | url = http://www.molcells.org/home/journal/include/downloadPdf.asp?articleuid={A158E3B4-2423-4806-9A30-4B93CDA76DA0} | url-status = dead | archive-url = https://web.archive.org/web/20110501181419/http://www.molcells.org/home/journal/include/downloadPdf.asp?articleuid=%7BA158E3B4-2423-4806-9A30-4B93CDA76DA0%7D | df = | archive-date = 1 May 2011 }}</ref>。然后，这种氨基酰tRNA成为核糖体的底物，核糖体利用信使RNA中的序列信息将氨基酸连接到伸长的蛋白质链上<ref>{{cite journal | vauthors = Lengyel P, Söll D | title = Mechanism of protein biosynthesis | journal = Bacteriological Reviews | volume = 33 | issue = 2 | pages = 264–301 | date = June 1969 | pmid = 4896351 | pmc = 378322 | doi = 10.1128/MMBR.33.2.264-301.1969 }}</ref>。

===Nucleotide synthesis and salvage===
核苷酸的合成和补救途径
{{further|Nucleotide salvage|Pyrimidine biosynthesis|Purine#Metabolism}}

更多信息：核苷酸补救途径，嘧啶的生物合成和嘌呤§代谢

Nucleotides are made from amino acids, carbon dioxide and [[formic acid]] in pathways that require large amounts of metabolic energy. Consequently, most organisms have efficient systems to salvage preformed nucleotides. [[Purine]]s are synthesized as [[nucleoside]]s (bases attached to [[ribose]]). Both [[adenine]] and [[guanine]] are made from the precursor nucleoside [[inosine]] monophosphate, which is synthesized using atoms from the amino acids [[glycine]], [[glutamine]], and [[aspartic acid]], as well as [[formate]] transferred from the [[coenzyme]] [[folic acid|tetrahydrofolate]]. [[Pyrimidine]]s, on the other hand, are synthesized from the base [[Pyrimidinecarboxylic acid|orotate]], which is formed from glutamine and aspartate.

Nucleotides are made from amino acids, carbon dioxide and formic acid in pathways that require large amounts of metabolic energy. Consequently, most organisms have efficient systems to salvage preformed nucleotides. Purines are synthesized as nucleosides (bases attached to ribose). Both adenine and guanine are made from the precursor nucleoside inosine monophosphate, which is synthesized using atoms from the amino acids glycine, glutamine, and aspartic acid, as well as formate transferred from the coenzyme tetrahydrofolate. Pyrimidines, on the other hand, are synthesized from the base orotate, which is formed from glutamine and aspartate.

核苷酸由氨基酸、二氧化碳和甲酸在需要大量代谢能量的途径中生成<ref name=Rudolph>{{cite journal | vauthors = Rudolph FB | title = The biochemistry and physiology of nucleotides | journal = The Journal of Nutrition | volume = 124 | issue = 1 Suppl | pages = 124S–127S | date = January 1994 | pmid = 8283301 | doi = 10.1093/jn/124.suppl_1.124S }} {{cite journal | vauthors = Zrenner R, Stitt M, Sonnewald U, Boldt R | title = Pyrimidine and purine biosynthesis and degradation in plants | journal = Annual Review of Plant Biology | volume = 57 | issue = | pages = 805–36 | year = 2006 | pmid = 16669783 | doi = 10.1146/annurev.arplant.57.032905.105421 }}</ref>。因此，大多数生物体都有有效的系统来挽救预先形成的核苷酸<ref name=Rudolph/><ref>{{cite journal | vauthors = Stasolla C, Katahira R, Thorpe TA, Ashihara H | title = Purine and pyrimidine nucleotide metabolism in higher plants | journal = Journal of Plant Physiology | volume = 160 | issue = 11 | pages = 1271–95 | date = November 2003 | pmid = 14658380 | doi = 10.1078/0176-1617-01169 }}</ref>。嘌呤以核苷的形式合成(碱基附着在核糖上)。腺嘌呤和鸟嘌呤都是由一磷酸核苷肌苷前体合成的<ref name="pmid 22531138">{{cite journal | vauthors = Davies O, Mendes P, Smallbone K, Malys N | title = Characterisation of multiple substrate-specific (d)ITP/(d)XTPase and modelling of deaminated purine nucleotide metabolism | journal = BMB Reports | volume = 45 | issue = 4 | pages = 259–64 | date = April 2012 | pmid = 22531138 | doi = 10.5483/BMBRep.2012.45.4.259 | url = http://wrap.warwick.ac.uk/49510/1/WRAP_Malys_%5B45-4%5D1204261917_%28259-264%29BMB_11-169.pdf }}</ref>，而前体是由甘氨酸、谷氨酰胺和天冬氨酸的原子合成的，从辅酶四氢叶酸转移来的甲酸酯也是如此。另一方面，嘧啶是由磷酸基合成的，而磷酸基是由谷氨酰胺和天门冬氨酸形成的<ref>{{cite journal | vauthors = Smith JL | title = Enzymes of nucleotide synthesis | journal = Current Opinion in Structural Biology | volume = 5 | issue = 6 | pages = 752–7 | date = December 1995 | pmid = 8749362 | doi = 10.1016/0959-440X(95)80007-7 }}</ref>。

==Xenobiotics and redox metabolism==
异种生物学和氧化还原代谢
{{further|Xenobiotic metabolism|Drug metabolism|Alcohol metabolism|Antioxidant}}

更多信息：异生物质代谢，药物代谢，酒精代谢和抗氧化剂

All organisms are constantly exposed to compounds that they cannot use as foods and would be harmful if they accumulated in cells, as they have no metabolic function. These potentially damaging compounds are called [[xenobiotic]]s. Xenobiotics such as [[drug|synthetic drugs]], [[poison|natural poisons]] and [[antibiotic]]s are detoxified by a set of xenobiotic-metabolizing enzymes. In humans, these include [[cytochrome P450|cytochrome P450 oxidases]], [[Glucuronosyltransferase|UDP-glucuronosyltransferases]], and [[glutathione S-transferase|glutathione ''S''-transferases]]. This system of enzymes acts in three stages to firstly oxidize the xenobiotic (phase I) and then conjugate water-soluble groups onto the molecule (phase II). The modified water-soluble xenobiotic can then be pumped out of cells and in multicellular organisms may be further metabolized before being excreted (phase III). In [[ecology]], these reactions are particularly important in microbial [[biodegradation]] of pollutants and the [[bioremediation]] of contaminated land and oil spills. Many of these microbial reactions are shared with multicellular organisms, but due to the incredible diversity of types of microbes these organisms are able to deal with a far wider range of xenobiotics than multicellular organisms, and can degrade even [[persistent organic pollutant]]s such as [[organochloride]] compounds.
All organisms are constantly exposed to compounds that they cannot use as foods and would be harmful if they accumulated in cells, as they have no metabolic function. These potentially damaging compounds are called xenobiotics. Xenobiotics such as synthetic drugs, natural poisons and antibiotics are detoxified by a set of xenobiotic-metabolizing enzymes. In humans, these include cytochrome P450 oxidases, UDP-glucuronosyltransferases, and glutathione S-transferases. This system of enzymes acts in three stages to firstly oxidize the xenobiotic (phase I) and then conjugate water-soluble groups onto the molecule (phase II). The modified water-soluble xenobiotic can then be pumped out of cells and in multicellular organisms may be further metabolized before being excreted (phase III). In ecology, these reactions are particularly important in microbial biodegradation of pollutants and the bioremediation of contaminated land and oil spills. Many of these microbial reactions are shared with multicellular organisms, but due to the incredible diversity of types of microbes these organisms are able to deal with a far wider range of xenobiotics than multicellular organisms, and can degrade even persistent organic pollutants such as organochloride compounds.

所有的生物都不断地接触到它们不能进食的化合物，如果它们在细胞中积累这些化合物就会被伤害，因为它们没有新陈代谢功能。这些具有潜在破坏性的化合物被称为异生物质<ref>{{cite journal | vauthors = Testa B, Krämer SD | title = The biochemistry of drug metabolism--an introduction: part 1. Principles and overview | journal = Chemistry & Biodiversity | volume = 3 | issue = 10 | pages = 1053–101 | date = October 2006 | pmid = 17193224 | doi = 10.1002/cbdv.200690111 | s2cid = 28872968 }}</ref>。合成药物、天然毒物和抗生素等异生物质是通过一系列异生物质代谢酶来解毒的。在人体中，这些酶包括细胞色素 P450氧化酶<ref>{{cite journal | vauthors = Danielson PB | title = The cytochrome P450 superfamily: biochemistry, evolution and drug metabolism in humans | journal = Current Drug Metabolism | volume = 3 | issue = 6 | pages = 561–97 | date = December 2002 | pmid = 12369887 | doi = 10.2174/1389200023337054 }}</ref>、UDP-葡萄糖醛酸转移酶<ref>{{cite journal | vauthors = King CD, Rios GR, Green MD, Tephly TR | title = UDP-glucuronosyltransferases | journal = Current Drug Metabolism | volume = 1 | issue = 2 | pages = 143–61 | date = September 2000 | pmid = 11465080 | doi = 10.2174/1389200003339171 }}</ref>和谷胱甘肽 s- 转移酶。这套酶系统的作用分为三个阶段<ref>{{cite journal | vauthors = Sheehan D, Meade G, Foley VM, Dowd CA | title = Structure, function and evolution of glutathione transferases: implications for classification of non-mammalian members of an ancient enzyme superfamily | journal = The Biochemical Journal | volume = 360 | issue = Pt 1 | pages = 1–16 | date = November 2001 | pmid = 11695986 | pmc = 1222196 | doi = 10.1042/0264-6021:3600001 }}</ref>，首先氧化异生物质(第一阶段) ，然后将水溶性基团共轭到分子上(第二阶段)。经过降解的水溶性异生物质随后会从细胞中泵出，对多细胞生物来说，还会在排出之前进一步代谢(第三阶段)。在生态学中，这些反应在微生物对污染物的生物降解以及污染土地和溢油的生物修复中尤为重要<ref>{{cite journal | vauthors = Galvão TC, Mohn WW, de Lorenzo V | title = Exploring the microbial biodegradation and biotransformation gene pool | journal = Trends in Biotechnology | volume = 23 | issue = 10 | pages = 497–506 | date = October 2005 | pmid = 16125262 | doi = 10.1016/j.tibtech.2005.08.002 }}</ref>。这些微生物反应中有许多是与多细胞生物相同的，但是由于微生物种类的惊人多样性，这些微生物能够处理比多细胞生物更广泛的异生物质，甚至能够降解有机氯化合物等持久性有机污染物<ref>{{cite journal | vauthors = Janssen DB, Dinkla IJ, Poelarends GJ, Terpstra P | title = Bacterial degradation of xenobiotic compounds: evolution and distribution of novel enzyme activities | journal = Environmental Microbiology | volume = 7 | issue = 12 | pages = 1868–82 | date = December 2005 | pmid = 16309386 | doi = 10.1111/j.1462-2920.2005.00966.x | url = https://pure.rug.nl/ws/files/3623678/2005EnvironMicrobiolJanssen.pdf }}</ref>
。

A related problem for [[aerobic organism]]s is [[oxidative stress]]. Here, processes including [[oxidative phosphorylation]] and the formation of [[disulfide bond]]s during [[protein folding]] produce [[reactive oxygen species]] such as [[hydrogen peroxide]]. These damaging oxidants are removed by [[antioxidant]] metabolites such as [[glutathione]] and enzymes such as [[catalase]]s and [[peroxidase]]s.

A related problem for aerobic organisms is oxidative stress. Here, processes including oxidative phosphorylation and the formation of disulfide bonds during protein folding produce reactive oxygen species such as hydrogen peroxide. These damaging oxidants are removed by antioxidant metabolites such as glutathione and enzymes such as catalases and peroxidases.

对于好氧生物来说，一个相关的问题是氧化应激<ref name=Davies>{{cite journal | vauthors = Davies KJ | title = Oxidative stress: the paradox of aerobic life | journal = Biochemical Society Symposium | volume = 61 | issue = | pages = 1–31 | year = 1995 | pmid = 8660387 | doi = 10.1042/bss0610001 }}</ref>。这个过程包括氧化磷酸化和蛋白质折叠时二硫键的形成，它产生了活性氧类（如过氧化氢）<ref>{{cite journal | vauthors = Tu BP, Weissman JS | title = Oxidative protein folding in eukaryotes: mechanisms and consequences | journal = The Journal of Cell Biology | volume = 164 | issue = 3 | pages = 341–6 | date = February 2004 | pmid = 14757749 | pmc = 2172237 | doi = 10.1083/jcb.200311055 }}</ref>。这些破坏性的氧化剂被抗氧化代谢物（如谷胱甘肽和酶）和酶（如过氧化氢酶和过氧化物酶）去除<ref name=Sies>{{cite journal | vauthors = Sies H | title = Oxidative stress: oxidants and antioxidants | journal = Experimental Physiology | volume = 82 | issue = 2 | pages = 291–5 | date = March 1997 | pmid = 9129943 | doi = 10.1113/expphysiol.1997.sp004024 | s2cid = 20240552 | url = http://ep.physoc.org/cgi/reprint/82/2/291.pdf | access-date = 9 March 2007 | url-status = dead | archive-url = https://web.archive.org/web/20090325001126/http://ep.physoc.org/cgi/reprint/82/2/291.pdf | archive-date = 25 March 2009 }}</ref><ref name=Vertuani>{{cite journal | vauthors = Vertuani S, Angusti A, Manfredini S | title = The antioxidants and pro-antioxidants network: an overview | journal = Current Pharmaceutical Design | volume = 10 | issue = 14 | pages = 1677–94 | year = 2004 | pmid = 15134565 | doi = 10.2174/1381612043384655 | s2cid = 43713549 }}</ref>。

==Thermodynamics of living organisms==
生命有机体的热力学
{{further|Biological thermodynamics}}

更多信息：生物热力学

Living organisms must obey the [[laws of thermodynamics]], which describe the transfer of heat and [[work (thermodynamics)|work]]. The [[second law of thermodynamics]] states that in any [[closed system]], the amount of [[entropy]] (disorder) cannot decrease. Although living organisms' amazing complexity appears to contradict this law, life is possible as all organisms are [[open system (systems theory)|open systems]] that exchange matter and energy with their surroundings. Thus living systems are not in [[Thermodynamic equilibrium|equilibrium]], but instead are [[dissipative system]]s that maintain their state of high complexity by causing a larger increase in the entropy of their environments. The metabolism of a cell achieves this by coupling the [[spontaneous process]]es of catabolism to the non-spontaneous processes of anabolism. In [[non-equilibrium thermodynamics|thermodynamic]] terms, metabolism maintains order by creating disorder.

Living organisms must obey the laws of thermodynamics, which describe the transfer of heat and work. The second law of thermodynamics states that in any closed system, the amount of entropy (disorder) cannot decrease. Although living organisms' amazing complexity appears to contradict this law, life is possible as all organisms are open systems that exchange matter and energy with their surroundings. Thus living systems are not in equilibrium, but instead are dissipative systems that maintain their state of high complexity by causing a larger increase in the entropy of their environments. The metabolism of a cell achieves this by coupling the spontaneous processes of catabolism to the non-spontaneous processes of anabolism. In thermodynamic terms, metabolism maintains order by creating disorder.

生命有机体一定会遵守热力学定律，该定律描述了热量和功的传递。热力学第二定律指出，在任何封闭系统中，熵的总量（混乱度）不会减少。尽管生物体惊人的复杂性似乎与这一定律相矛盾，但生命是可能的，因为它们是与环境交换物质和能量的开放系统。也就是说，生命系统并不处于平衡状态，而是耗散系统，它通过大量增加环境熵来维持其高度复杂的状态<ref>{{cite journal | vauthors = von Stockar U, Liu J | title = Does microbial life always feed on negative entropy? Thermodynamic analysis of microbial growth | journal = Biochimica et Biophysica Acta (BBA) - Bioenergetics | volume = 1412 | issue = 3 | pages = 191–211 | date = August 1999 | pmid = 10482783 | doi = 10.1016/S0005-2728(99)00065-1 }}</ref>。细胞的新陈代谢通过将分解代谢的自发过程和合成代谢的非自发过程进行耦合来实现这一点。从热力学的角度来看，新陈代谢通过制造混乱来维持秩序<ref>{{cite journal | vauthors = Demirel Y, Sandler SI | title = Thermodynamics and bioenergetics | journal = Biophysical Chemistry | volume = 97 | issue = 2–3 | pages = 87–111 | date = June 2002 | pmid = 12050002 | doi = 10.1016/S0301-4622(02)00069-8 | url = https://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=1006&context=chemengthermalmech }}</ref>。

==Regulation and control==
调控
{{further|Metabolic pathway|Metabolic control analysis|Hormone|Regulatory enzymes|Cell signaling}}

更多信息：代谢途径，代谢控制分析，激素，调节酶和细胞信号转导

As the environments of most organisms are constantly changing, the reactions of metabolism must be finely [[Control theory|regulated]] to maintain a constant set of conditions within cells, a condition called [[homeostasis]]. Metabolic regulation also allows organisms to respond to signals and interact actively with their environments. Two closely linked concepts are important for understanding how metabolic pathways are controlled. Firstly, the ''regulation'' of an enzyme in a pathway is how its activity is increased and decreased in response to signals. Secondly, the ''control'' exerted by this enzyme is the effect that these changes in its activity have on the overall rate of the pathway (the [[flux]] through the pathway). For example, an enzyme may show large changes in activity (''i.e.'' it is highly regulated) but if these changes have little effect on the flux of a metabolic pathway, then this enzyme is not involved in the control of the pathway.

As the environments of most organisms are constantly changing, the reactions of metabolism must be finely regulated to maintain a constant set of conditions within cells, a condition called homeostasis. Metabolic regulation also allows organisms to respond to signals and interact actively with their environments. Two closely linked concepts are important for understanding how metabolic pathways are controlled. Firstly, the regulation of an enzyme in a pathway is how its activity is increased and decreased in response to signals. Secondly, the control exerted by this enzyme is the effect that these changes in its activity have on the overall rate of the pathway (the flux through the pathway). For example, an enzyme may show large changes in activity (i.e. it is highly regulated) but if these changes have little effect on the flux of a metabolic pathway, then this enzyme is not involved in the control of the pathway.

由于大多数生物体的环境是不断变化的，因此它们必须对新陈代谢的反应进行精细的调节，以维持细胞内一系列恒定的条件，这种条件称为稳态<ref>{{cite journal | vauthors = Albert R | title = Scale-free networks in cell biology | journal = Journal of Cell Science | volume = 118 | issue = Pt 21 | pages = 4947–57 | date = November 2005 | pmid = 16254242 | doi = 10.1242/jcs.02714 | arxiv = q-bio/0510054 | s2cid = 3001195 | bibcode = 2005q.bio....10054A }}</ref><ref>{{cite journal | vauthors = Brand MD | title = Regulation analysis of energy metabolism | journal = The Journal of Experimental Biology | volume = 200 | issue = Pt 2 | pages = 193–202 | date = January 1997 | pmid = 9050227 | url = http://jeb.biologists.org/cgi/reprint/200/2/193 }}</ref>。代谢调节也使生物体能够对信号作出反应，并与环境积极互动。有两个密切相关的概念对于理解“代谢途径是如何被控制的”十分重要<ref>{{cite journal | vauthors = Soyer OS, Salathé M, Bonhoeffer S | title = Signal transduction networks: topology, response and biochemical processes | journal = Journal of Theoretical Biology | volume = 238 | issue = 2 | pages = 416–25 | date = January 2006 | pmid = 16045939 | doi = 10.1016/j.jtbi.2005.05.030 }}</ref>。首先，途径中酶的调节是指其活性如何响应信号从而增加和减少。其次，这种酶所施加的控制是指它的活性变化对通路的总体速率（通过通路的通量）的影响<ref name=Salter>{{cite journal | vauthors = Salter M, Knowles RG, Pogson CI | title = Metabolic control | journal = Essays in Biochemistry | volume = 28 | issue = | pages = 1–12 | year = 1994 | pmid = 7925313 }}</ref>。例如，一种酶可能表现出很大的活性变化(即它是高度受控的)，但如果这些变化对某一代谢途径的通量影响不大，那么这种酶就不参与该途径的控制<ref>{{cite journal | vauthors = Westerhoff HV, Groen AK, Wanders RJ | title = Modern theories of metabolic control and their applications (review) | journal = Bioscience Reports | volume = 4 | issue = 1 | pages = 1–22 | date = January 1984 | pmid = 6365197 | doi = 10.1007/BF01120819 | s2cid = 27791605 }}</ref>。

[[File:Insulin glucose metabolism ZP.svg|thumb|right|upright=1.35|胰岛素对葡萄糖摄取和代谢的影响。胰岛素与其受体（1）结合，继而启动许多蛋白质激活级联反应（2）。其中包括：Glut-4转运蛋白向[[质膜]]的转运和葡萄糖的流入（3），[[糖原]]合成（4），[[糖酵解]]（5）和[[脂肪酸]]合成（6）。]]

There are multiple levels of metabolic regulation. In intrinsic regulation, the metabolic pathway self-regulates to respond to changes in the levels of substrates or products; for example, a decrease in the amount of product can increase the [[flux]] through the pathway to compensate. This type of regulation often involves [[allosteric regulation]] of the activities of multiple enzymes in the pathway. Extrinsic control involves a cell in a multicellular organism changing its metabolism in response to signals from other cells. These signals are usually in the form of water soluble messengers such as [[hormone]]s and [[growth factor]]s and are detected by specific [[receptor (biochemistry)|receptors]] on the cell surface. These signals are then transmitted inside the cell by [[second messenger system]]s that often involved the [[phosphorylation]] of proteins.

There are multiple levels of metabolic regulation. In intrinsic regulation, the metabolic pathway self-regulates to respond to changes in the levels of substrates or products; for example, a decrease in the amount of product can increase the flux through the pathway to compensate. Extrinsic control involves a cell in a multicellular organism changing its metabolism in response to signals from other cells. These signals are usually in the form of water soluble messengers such as hormones and growth factors and are detected by specific receptors on the cell surface. These signals are then transmitted inside the cell by second messenger systems that often involved the phosphorylation of proteins.

新陈代谢调节有多个层次。在内在调节中，代谢途径自我调节，以应对底物或产物数量的变化；例如，产物数量的减少可以增加通过该途径的通量以进行补偿<ref name=Salter/>。外在控制是指多细胞生物体中的一个细胞根据来自其他细胞的信号改变其代谢<ref>{{cite journal | vauthors = Fell DA, Thomas S | title = Physiological control of metabolic flux: the requirement for multisite modulation | journal = The Biochemical Journal | volume = 311 ( Pt 1) | issue = Pt 1 | pages = 35–9 | date = October 1995 | pmid = 7575476 | pmc = 1136115 | doi = 10.1042/bj3110035 }}</ref>。这些信号通常以水溶性信使的形式出现（如激素和生长因子）<ref>{{cite journal | vauthors = Hendrickson WA | title = Transduction of biochemical signals across cell membranes | journal = Quarterly Reviews of Biophysics | volume = 38 | issue = 4 | pages = 321–30 | date = November 2005 | pmid = 16600054 | doi = 10.1017/S0033583506004136 }}</ref>，并被细胞表面的特定受体检测到。然后，这些信号通过第二信使系统在细胞内传递，该系统通常涉及蛋白质的磷酸化<ref>{{cite journal | vauthors = Cohen P | title = The regulation of protein function by multisite phosphorylation--a 25 year update | journal = Trends in Biochemical Sciences | volume = 25 | issue = 12 | pages = 596–601 | date = December 2000 | pmid = 11116185 | doi = 10.1016/S0968-0004(00)01712-6 }}</ref>。

A very well understood example of extrinsic control is the regulation of glucose metabolism by the hormone [[insulin]]. Insulin is produced in response to rises in [[blood sugar|blood glucose levels]]. Binding of the hormone to [[insulin receptor]]s on cells then activates a cascade of [[protein kinase]]s that cause the cells to take up glucose and convert it into storage molecules such as fatty acids and [[glycogen]]. The metabolism of glycogen is controlled by activity of [[phosphorylase]], the enzyme that breaks down glycogen, and [[glycogen synthase]], the enzyme that makes it. These enzymes are regulated in a reciprocal fashion, with phosphorylation inhibiting glycogen synthase, but activating phosphorylase. Insulin causes glycogen synthesis by activating [[phosphatase|protein phosphatases]] and producing a decrease in the phosphorylation of these enzymes.

A very well understood example of extrinsic control is the regulation of glucose metabolism by the hormone insulin. Insulin is produced in response to rises in blood glucose levels. Binding of the hormone to insulin receptors on cells then activates a cascade of protein kinases that cause the cells to take up glucose and convert it into storage molecules such as fatty acids and glycogen. The metabolism of glycogen is controlled by activity of phosphorylase, the enzyme that breaks down glycogen, and glycogen synthase, the enzyme that makes it. These enzymes are regulated in a reciprocal fashion, with phosphorylation inhibiting glycogen synthase, but activating phosphorylase. Insulin causes glycogen synthesis by activating protein phosphatases and producing a decrease in the phosphorylation of these enzymes.

一个非常好理解的外在控制的例子是激素胰岛素对葡萄糖代谢的调节<ref>{{cite journal | vauthors = Lienhard GE, Slot JW, James DE, Mueckler MM | title = How cells absorb glucose | journal = Scientific American | volume = 266 | issue = 1 | pages = 86–91 | date = January 1992 | pmid = 1734513 | doi = 10.1038/scientificamerican0192-86 | bibcode = 1992SciAm.266a..86L }}</ref>。胰岛素是在血糖升高时产生的。胰岛素与细胞上的胰岛素受体结合，然后激活一连串的蛋白激酶，使细胞吸收葡萄糖，并将其转化为储存分子（如脂肪酸和糖原）<ref>{{cite journal | vauthors = Roach PJ | title = Glycogen and its metabolism | journal = Current Molecular Medicine | volume = 2 | issue = 2 | pages = 101–20 | date = March 2002 | pmid = 11949930 | doi = 10.2174/1566524024605761 }}</ref>。糖原的新陈代谢受到分解糖原的磷酸化酶和制造糖原的糖原合成酶的活性控制。这些酶的调节方式是相互的，磷酸化作用抑制糖原合成酶，但激活磷酸化酶。胰岛素通过激活蛋白磷酸酶使这些酶的磷酸化程度降低，从而触发糖原合成<ref>{{cite journal | vauthors = Newgard CB, Brady MJ, O'Doherty RM, Saltiel AR | title = Organizing glucose disposal: emerging roles of the glycogen targeting subunits of protein phosphatase-1 | journal = Diabetes | volume = 49 | issue = 12 | pages = 1967–77 | date = December 2000 | pmid = 11117996 | doi = 10.2337/diabetes.49.12.1967 | url = http://diabetes.diabetesjournals.org/cgi/reprint/49/12/1967.pdf }}</ref>。

==Evolution==
演化
{{further|Molecular evolution|Phylogenetics}}

更多信息：分子进化与系统发育

[[File:Tree of life int.svg|thumb|right|upright=1.8|[[演化树显示了来自全部三个生命领域的生物体的共同祖先。[[细菌]]呈蓝色，[[真核生物]]呈红色，[[古菌]]呈绿色。树木周围显示了一些门的相对位置。]]

Evolutionary tree showing the common ancestry of organisms from all three domains of life. Bacteria are colored blue, eukaryotes red, and archaea green. Relative positions of some of the phyla included are shown around the tree.]]

The central pathways of metabolism described above, such as glycolysis and the citric acid cycle, are present in all [[Three-domain system|three domains]] of living things and were present in the [[last universal common ancestor]]. This universal ancestral cell was [[prokaryote|prokaryotic]] and probably a [[methanogen]] that had extensive amino acid, nucleotide, carbohydrate and lipid metabolism. The retention of these ancient pathways during later [[evolution]] may be the result of these reactions having been an optimal solution to their particular metabolic problems, with pathways such as glycolysis and the citric acid cycle producing their end products highly efficiently and in a minimal number of steps. The first pathways of enzyme-based metabolism may have been parts of [[purine]] nucleotide metabolism, while previous metabolic pathways were a part of the ancient [[RNA world hypothesis|RNA world]].

The central pathways of metabolism described above, such as glycolysis and the citric acid cycle, are present in all three domains of living things and were present in the last universal common ancestor.This universal ancestral cell was prokaryotic and probably a methanogen that had extensive amino acid, nucleotide, carbohydrate and lipid metabolism.The retention of these ancient pathways during later evolution may be the result of these reactions having been an optimal solution to their particular metabolic problems, with pathways such as glycolysis and the citric acid cycle producing their end products highly efficiently and in a minimal number of steps.The first pathways of enzyme-based metabolism may have been parts of purine nucleotide metabolism, while previous metabolic pathways were a part of the ancient RNA world.

上述代谢的主要途径，如糖酵解和柠檬酸循环，存在于生物的全部三个领域中，并存在于最后的普遍共同祖先中。这种普遍的祖先细胞是原核生物<ref name=SmithE/><ref>{{cite journal | vauthors = Romano AH, Conway T | title = Evolution of carbohydrate metabolic pathways | journal = Research in Microbiology | volume = 147 | issue = 6–7 | pages = 448–55 | year = 1996 | pmid = 9084754 | doi = 10.1016/0923-2508(96)83998-2 }}</ref>，也许是一种具有广泛的氨基酸、核苷酸、碳水化合物和脂质代谢的产烷菌<ref>{{cite book |author=Koch A |title=How did bacteria come to be? |journal=Adv Microb Physiol |volume=40 |pages=353–99 |year=1998 |pmid=9889982 |doi=10.1016/S0065-2911(08)60135-6 |series=Advances in Microbial Physiology |isbn=978-0-12-027740-7}}</ref><ref>{{cite journal | vauthors = Ouzounis C, Kyrpides N | title = The emergence of major cellular processes in evolution | journal = FEBS Letters | volume = 390 | issue = 2 | pages = 119–23 | date = July 1996 | pmid = 8706840 | doi = 10.1016/0014-5793(96)00631-X | s2cid = 39128865 }}</ref>。在后来的进化过程中，这些古老的途径之所以得以保留，可能是因为这些反应为它们特定的代谢问题提供了最佳解决方案，这些途径（如糖酵解和三羧酸循环）以最少的步骤高效地产生它们的最终产物。最初的基于酶的代谢途径可能是嘌呤核苷酸代谢的一部分<ref name=Ebenhoh/><ref name=Cascante/>，而之前的代谢途径是远古RNA界的一部分<ref>{{cite journal | vauthors = Caetano-Anollés G, Kim HS, Mittenthal JE | title = The origin of modern metabolic networks inferred from phylogenomic analysis of protein architecture | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 104 | issue = 22 | pages = 9358–63 | date = May 2007 | pmid = 17517598 | pmc = 1890499 | doi = 10.1073/pnas.0701214104 | bibcode = 2007PNAS..104.9358C }}</ref>。

Many models have been proposed to describe the mechanisms by which novel metabolic pathways evolve. These include the sequential addition of novel enzymes to a short ancestral pathway, the duplication and then divergence of entire pathways as well as the recruitment of pre-existing enzymes and their assembly into a novel reaction pathway. The relative importance of these mechanisms is unclear, but genomic studies have shown that enzymes in a pathway are likely to have a shared ancestry, suggesting that many pathways have evolved in a step-by-step fashion with novel functions created from pre-existing steps in the pathway. An alternative model comes from studies that trace the evolution of proteins' structures in metabolic networks, this has suggested that enzymes are pervasively recruited, borrowing enzymes to perform similar functions in different metabolic pathways (evident in the [[MANET database]]). These recruitment processes result in an evolutionary enzymatic mosaic. A third possibility is that some parts of metabolism might exist as "modules" that can be reused in different pathways and perform similar functions on different molecules.

Many models have been proposed to describe the mechanisms by which novel metabolic pathways evolve. These include the sequential addition of novel enzymes to a short ancestral pathway, the duplication and then divergence of entire pathways as well as the recruitment of pre-existing enzymes and their assembly into a novel reaction pathway. The relative importance of these mechanisms is unclear, but genomic studies have shown that enzymes in a pathway are likely to have a shared ancestry, suggesting that many pathways have evolved in a step-by-step fashion with novel functions created from pre-existing steps in the pathway. An alternative model comes from studies that trace the evolution of proteins' structures in metabolic networks, this has suggested that enzymes are pervasively recruited, borrowing enzymes to perform similar functions in different metabolic pathways (evident in the MANET database) These recruitment processes result in an evolutionary enzymatic mosaic. A third possibility is that some parts of metabolism might exist as "modules" that can be reused in different pathways and perform similar functions on different molecules.

人们提出了许多模型来描述新代谢途径的演变机制。其中包括将新的酶顺序添加到一个短的祖传途径，整个途径的复制和分化，吸纳原有的酶或者把这些机制组装成新的反应途径。这些机制的相对重要性尚不清楚<ref>{{cite journal | vauthors = Schmidt S, Sunyaev S, Bork P, Dandekar T | title = Metabolites: a helping hand for pathway evolution? | journal = Trends in Biochemical Sciences | volume = 28 | issue = 6 | pages = 336–41 | date = June 2003 | pmid = 12826406 | doi = 10.1016/S0968-0004(03)00114-2 }}</ref>，但基因组研究表明，一条途径中的酶很可能有共同的祖先，这意味着许多途径是逐步进化而来的，途径中预先存在的步骤创造出了新的功能。另一种模型来自于追踪代谢网络中蛋白质结构演化的研究<ref>{{cite journal | vauthors = Light S, Kraulis P | title = Network analysis of metabolic enzyme evolution in Escherichia coli | journal = BMC Bioinformatics | volume = 5 | pages = 15 | date = February 2004 | pmid = 15113413 | pmc = 394313 | doi = 10.1186/1471-2105-5-15 }} {{cite journal | vauthors = Alves R, Chaleil RA, Sternberg MJ | title = Evolution of enzymes in metabolism: a network perspective | journal = Journal of Molecular Biology | volume = 320 | issue = 4 | pages = 751–70 | date = July 2002 | pmid = 12095253 | doi = 10.1016/S0022-2836(02)00546-6 }}</ref>，它指出酶被普遍利用，生物体借用酶在不同的代谢途径中执行相似的功能(在 MANET 数据库中显而易见)<ref>{{cite journal | vauthors = Kim HS, Mittenthal JE, Caetano-Anollés G | title = MANET: tracing evolution of protein architecture in metabolic networks | journal = BMC Bioinformatics | volume = 7 | pages = 351 | date = July 2006 | pmid = 16854231 | pmc = 1559654 | doi = 10.1186/1471-2105-7-351 }}</ref>。这些征用过程导致了进化酶的嵌合<ref>{{cite journal | vauthors = Teichmann SA, Rison SC, Thornton JM, Riley M, Gough J, Chothia C | title = Small-molecule metabolism: an enzyme mosaic | journal = Trends in Biotechnology | volume = 19 | issue = 12 | pages = 482–6 | date = December 2001 | pmid = 11711174 | doi = 10.1016/S0167-7799(01)01813-3 }}</ref>。第三种可能性是，新陈代谢的某些部分可能作为“模块”存在，可以在不同的途径中重复使用，并对不同的分子执行类似的功能<ref>{{cite journal | vauthors = Spirin V, Gelfand MS, Mironov AA, Mirny LA | title = A metabolic network in the evolutionary context: multiscale structure and modularity | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 103 | issue = 23 | pages = 8774–9 | date = June 2006 | pmid = 16731630 | pmc = 1482654 | doi = 10.1073/pnas.0510258103 | bibcode = 2006PNAS..103.8774S }}</ref>。

As well as the evolution of new metabolic pathways, evolution can also cause the loss of metabolic functions. For example, in some [[parasite]]s metabolic processes that are not essential for survival are lost and preformed amino acids, nucleotides and carbohydrates may instead be scavenged from the [[host (biology)|host]]. Similar reduced metabolic capabilities are seen in [[endosymbiont|endosymbiotic]] organisms.

As well as the evolution of new metabolic pathways, evolution can also cause the loss of metabolic functions. For example, in some parasites metabolic processes that are not essential for survival are lost and preformed amino acids, nucleotides and carbohydrates may instead be scavenged from the host. Similar reduced metabolic capabilities are seen in endosymbiotic organisms.

除了新的代谢途径的进化，演化也会导致代谢功能的丧失。例如，在某些寄生物中，一些并非生存必需的代谢过程丢失了，而预先形成的氨基酸、核苷酸和碳水化合物可能会从寄主那里被清除<ref>{{cite journal | vauthors = Lawrence JG | title = Common themes in the genome strategies of pathogens | journal = Current Opinion in Genetics & Development | volume = 15 | issue = 6 | pages = 584–8 | date = December 2005 | pmid = 16188434 | doi = 10.1016/j.gde.2005.09.007 }} {{cite journal | vauthors = Wernegreen JJ | title = For better or worse: genomic consequences of intracellular mutualism and parasitism | journal = Current Opinion in Genetics & Development | volume = 15 | issue = 6 | pages = 572–83 | date = December 2005 | pmid = 16230003 | doi = 10.1016/j.gde.2005.09.013 }}</ref>。在内共生生物体中也可以看到类似的代谢能力下降<ref>{{cite journal | vauthors = Pál C, Papp B, Lercher MJ, Csermely P, Oliver SG, Hurst LD | title = Chance and necessity in the evolution of minimal metabolic networks | journal = Nature | volume = 440 | issue = 7084 | pages = 667–70 | date = March 2006 | pmid = 16572170 | doi = 10.1038/nature04568 | s2cid = 4424895 | bibcode = 2006Natur.440..667P }}</ref>。

==Investigation and manipulation==
调查和操纵
{{further|Protein methods|Proteomics|Metabolomics|Metabolic network modelling}}

更多信息：蛋白质方法，蛋白质组学，代谢组学和代谢网络建模

[[File:A thaliana metabolic network.png|thumb|upright=1.35|right|[[拟南芥]][[三羧酸循环]]的[[代谢网络]]。[[酶]]和[[代谢物]]显示为红色方块，它们之间的相互作用显示为黑线。]]

Classically, metabolism is studied by a [[reductionism|reductionist]] approach that focuses on a single metabolic pathway. Particularly valuable is the use of [[radioactive tracer]]s at the whole-organism, tissue and cellular levels, which define the paths from precursors to final products by identifying radioactively labelled intermediates and products. The enzymes that catalyze these chemical reactions can then be [[protein purification|purified]] and their [[enzyme kinetics|kinetics]] and responses to [[enzyme inhibitor|inhibitors]] investigated. A parallel approach is to identify the small molecules in a cell or tissue; the complete set of these molecules is called the [[metabolome]]. Overall, these studies give a good view of the structure and function of simple metabolic pathways, but are inadequate when applied to more complex systems such as the metabolism of a complete cell.

Classically, metabolism is studied by a reductionist approach that focuses on a single metabolic pathway. Particularly valuable is the use of radioactive tracers at the whole-organism, tissue and cellular levels, which define the paths from precursors to final products by identifying radioactively labelled intermediates and products. The enzymes that catalyze these chemical reactions can then be purified and their kinetics and responses to inhibitors investigated. A parallel approach is to identify the small molecules in a cell or tissue; the complete set of these molecules is called the metabolome. Overall, these studies give a good view of the structure and function of simple metabolic pathways, but are inadequate when applied to more complex systems such as the metabolism of a complete cell.

传统上，新陈代谢的研究采用还原法，侧重于单一的新陈代谢途径。特别有价值的是在整个有机体、组织和细胞水平上使用放射性示踪剂，通过追踪携带放射性标记的中间物和产品来获知从前体到最终产品的路径<ref>{{cite journal | vauthors = Rennie MJ | title = An introduction to the use of tracers in nutrition and metabolism | journal = The Proceedings of the Nutrition Society | volume = 58 | issue = 4 | pages = 935–44 | date = November 1999 | pmid = 10817161 | doi = 10.1017/S002966519900124X | doi-access = free }}</ref>。然后可以纯化催化这些化学反应的酶，并研究其动力学和对抑制剂的反应。一个并行的方法是识别细胞或组织中的小分子；这些分子的完整集合被称为代谢组。总的来说，这些研究可以很好地了解简单代谢途径的结构和功能，但当应用于更复杂的系统（如一个完整细胞的代谢时），这些研究是不够的<ref>{{cite journal | vauthors = Phair RD | title = Development of kinetic models in the nonlinear world of molecular cell biology | journal = Metabolism | volume = 46 | issue = 12 | pages = 1489–95 | date = December 1997 | pmid = 9439549 | doi = 10.1016/S0026-0495(97)90154-2 }}</ref>。

An idea of the complexity of the [[metabolic network]]s in cells that contain thousands of different enzymes is given by the figure showing the interactions between just 43 proteins and 40 metabolites to the right: the sequences of genomes provide lists containing anything up to 26.500 genes. However, it is now possible to use this genomic data to reconstruct complete networks of biochemical reactions and produce more [[Holism|holistic]] mathematical models that may explain and predict their behavior. These models are especially powerful when used to integrate the pathway and metabolite data obtained through classical methods with data on [[gene expression]] from [[proteomics|proteomic]] and [[DNA microarray]] studies. Using these techniques, a model of human metabolism has now been produced, which will guide future drug discovery and biochemical research. These models are now used in [[Network theory|network analysis]], to classify human diseases into groups that share common proteins or metabolites.

An idea of the complexity of the metabolic networks in cells that contain thousands of different enzymes is given by the figure showing the interactions between just 43 proteins and 40 metabolites to the right: the sequences of genomes provide lists containing anything up to 26.500 genes. However, it is now possible to use this genomic data to reconstruct complete networks of biochemical reactions and produce more holistic mathematical models that may explain and predict their behavior. These models are especially powerful when used to integrate the pathway and metabolite data obtained through classical methods with data on gene expression from proteomic and DNA microarray studies. Using these techniques, a model of human metabolism has now been produced, which will guide future drug discovery and biochemical research. These models are now used in network analysis, to classify human diseases into groups that share common proteins or metabolites.

细胞中包含数千种不同酶的代谢网络，这种复杂性概念可以在右图中看到，右图显示了43种蛋白质和40种代谢物之间的相互作用: 基因组序列提供了包含26.500个基因的列表<ref>{{cite journal | vauthors = Sterck L, Rombauts S, Vandepoele K, Rouzé P, Van de Peer Y | title = How many genes are there in plants (... and why are they there)? | journal = Current Opinion in Plant Biology | volume = 10 | issue = 2 | pages = 199–203 | date = April 2007 | pmid = 17289424 | doi = 10.1016/j.pbi.2007.01.004 }}</ref>。然而，现在能够利用这些基因组数据来重建完整的生化反应网络，并产生更全面的数学模型来解释和预测它们的行为。这些模型在用于整合通过经典方法获得的途径和代谢物数据以及蛋白质组学和DNA微阵列研究的基因表达数据时特别强大<ref>{{cite journal | vauthors = Borodina I, Nielsen J | title = From genomes to in silico cells via metabolic networks | journal = Current Opinion in Biotechnology | volume = 16 | issue = 3 | pages = 350–5 | date = June 2005 | pmid = 15961036 | doi = 10.1016/j.copbio.2005.04.008 }}</ref>。利用这些技术<ref>{{cite journal | vauthors = Gianchandani EP, Brautigan DL, Papin JA | title = Systems analyses characterize integrated functions of biochemical networks | journal = Trends in Biochemical Sciences | volume = 31 | issue = 5 | pages = 284–91 | date = May 2006 | pmid = 16616498 | doi = 10.1016/j.tibs.2006.03.007 }}</ref>，目前已经产生了一个人类代谢的模型，这将指导未来的药物发现和生化研究。这些模型现在被用于网络分析<ref>{{cite journal | vauthors = Duarte NC, Becker SA, Jamshidi N, Thiele I, Mo ML, Vo TD, Srivas R, Palsson BØ | display-authors = 6 | title = Global reconstruction of the human metabolic network based on genomic and bibliomic data | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 104 | issue = 6 | pages = 1777–82 | date = February 2007 | pmid = 17267599 | pmc = 1794290 | doi = 10.1073/pnas.0610772104 | bibcode = 2007PNAS..104.1777D }}</ref>，将人类疾病划分为具有共同蛋白质或代谢物的群体<ref>{{cite journal | vauthors = Goh KI, Cusick ME, Valle D, Childs B, Vidal M, Barabási AL | title = The human disease network | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 104 | issue = 21 | pages = 8685–90 | date = May 2007 | pmid = 17502601 | pmc = 1885563 | doi = 10.1073/pnas.0701361104 | bibcode = 2007PNAS..104.8685G }}</ref><ref>{{cite journal | vauthors = Lee DS, Park J, Kay KA, Christakis NA, Oltvai ZN, Barabási AL | title = The implications of human metabolic network topology for disease comorbidity | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 105 | issue = 29 | pages = 9880–5 | date = July 2008 | pmid = 18599447 | pmc = 2481357 | doi = 10.1073/pnas.0802208105 | url = http://www.pnas.org/lookup/pmid?view=long&pmid=18599447 | bibcode = 2008PNAS..105.9880L }}</ref>。

Bacterial metabolic networks are a striking example of [[Bow tie (biology)|bow-tie]] organization, an architecture able to input a wide range of nutrients and produce a large variety of products and complex macromolecules using a relatively few intermediate common currencies.

Bacterial metabolic networks are a striking example of bow-tie organization, an architecture able to input a wide range of nutrients and produce a large variety of products and complex macromolecules using a relatively few intermediate common currencies.

细菌代谢网络是蝴蝶结结构<ref name="pmid15331224">{{cite journal | vauthors = Csete M, Doyle J | title = Bow ties, metabolism and disease | journal = Trends in Biotechnology | volume = 22 | issue = 9 | pages = 446–50 | date = September 2004 | pmid = 15331224 | pmc = | doi = 10.1016/j.tibtech.2004.07.007 }}</ref><ref name="PMID12874056">{{cite journal | vauthors = Ma HW, Zeng AP | title = The connectivity structure, giant strong component and centrality of metabolic networks | journal = Bioinformatics | volume = 19 | issue = 11 | pages = 1423–30 | date = July 2003 | pmid = 12874056 | doi = 10.1093/bioinformatics/btg177 | citeseerx = 10.1.1.605.8964 }}</ref><ref name="PMID16916470">{{cite journal | vauthors = Zhao J, Yu H, Luo JH, Cao ZW, Li YX | title = Hierarchical modularity of nested bow-ties in metabolic networks | journal = BMC Bioinformatics | volume = 7 | pages = 386 | date = August 2006 | pmid = 16916470 | pmc = 1560398 | doi = 10.1186/1471-2105-7-386 | arxiv = q-bio/0605003 | bibcode = 2006q.bio.....5003Z }}</ref>的一个突出例子，这种架构能够输入多种营养物质，并利用相对较少的中间通货生产出大量产品和复杂的大分子。

A major technological application of this information is [[metabolic engineering]]. Here, organisms such as [[yeast]], plants or [[bacteria]] are genetically modified to make them more useful in [[biotechnology]] and aid the production of [[drug]]s such as [[antibiotic]]s or industrial chemicals such as [[1,3-Propanediol|1,3-propanediol]] and [[shikimic acid]]. These genetic modifications usually aim to reduce the amount of energy used to produce the product, increase yields and reduce the production of wastes.

A major technological application of this information is metabolic engineering. Here, organisms such as yeast, plants or bacteria are genetically modified to make them more useful in biotechnology and aid the production of drugs such as antibiotics or industrial chemicals such as 1,3-propanediol and shikimic acid. These genetic modifications usually aim to reduce the amount of energy used to produce the product, increase yields and reduce the production of wastes.

这些信息的一个主要技术应用是代谢工程学。在应用中，酵母、植物或细菌等生物体都可经过基因改造，使它们在生物技术方面更有用处，同时有助于生产抗生素等药物或工业化学品（如1,3- 丙二醇和莽草酸）<ref>{{cite journal | vauthors = Thykaer J, Nielsen J | title = Metabolic engineering of beta-lactam production | journal = Metabolic Engineering | volume = 5 | issue = 1 | pages = 56–69 | date = January 2003 | pmid = 12749845 | doi = 10.1016/S1096-7176(03)00003-X }}
{{cite journal | vauthors = González-Pajuelo M, Meynial-Salles I, Mendes F, Andrade JC, Vasconcelos I, Soucaille P | title = Metabolic engineering of Clostridium acetobutylicum for the industrial production of 1,3-propanediol from glycerol | journal = Metabolic Engineering | volume = 7 | issue = 5–6 | pages = 329–36 | year = 2005 | pmid = 16095939 | doi = 10.1016/j.ymben.2005.06.001 | hdl-access = free | hdl = 10400.14/3388 }}
{{cite journal | vauthors = Krämer M, Bongaerts J, Bovenberg R, Kremer S, Müller U, Orf S, Wubbolts M, Raeven L | display-authors = 6 | title = Metabolic engineering for microbial production of shikimic acid | journal = Metabolic Engineering | volume = 5 | issue = 4 | pages = 277–83 | date = October 2003 | pmid = 14642355 | doi = 10.1016/j.ymben.2003.09.001 }}</ref>。这些基因改造通常旨在减少生产产品所使用的能源，提高产量和减少废物的产生<ref>{{cite journal | vauthors = Koffas M, Roberge C, Lee K, Stephanopoulos G | title = Metabolic engineering | journal = Annual Review of Biomedical Engineering | volume = 1 | issue = | pages = 535–57 | year = 1999 | pmid = 11701499 | doi = 10.1146/annurev.bioeng.1.1.535 | s2cid = 11814282 }}</ref>。

==History==
历史
{{further|History of biochemistry|History of molecular biology}}

更多信息：生物化学的历史和分子生物学的历史

The term ''metabolism'' is derived from [[French language|French]] "métabolisme" or [[Ancient Greek]] μεταβολή – "Metabole" for "a change" which derived from μεταβάλλ –"Metaballein" means "To change"

The term metabolism is derived from French "métabolisme" or Ancient Greek μεταβολή – "Metabole" for "a change" which derived from μεταβάλλ –"Metaballein" means "To change"

新陈代谢这一术语源于法语“ métabolisme”或古希腊语 μταβoλλ -“Metabole”意为某种改变，它源自意为“去改变”的“ Metaballein”<ref>{{Cite web|title=metabolism {{!}} Origin and meaning of metabolism by Online Etymology Dictionary|url=https://www.etymonline.com/word/metabolism|access-date=2020-07-23|website=www.etymonline.com|language=en}}</ref>

[[File:Aristotle's metabolism.png|thumb|right|upright=1.4|亚里士多德Aristotle的新陈代谢是一个开放性的流动模型。]]

===Greek philosophy===
希腊哲学
[[Aristotle]]'s ''[[The Parts of Animals]]'' sets out enough details of [[Aristotle's biology|his views on metabolism]] for an open flow model to be made. He believed that at each stage of the process, materials from food were transformed, with heat being released as the [[classical element]] of fire, and residual materials being excreted as urine, bile, or faeces.

Aristotle's The Parts of Animals sets out enough details of his views on metabolism for an open flow model to be made. He believed that at each stage of the process, materials from food were transformed, with heat being released as the classical element of fire, and residual materials being excreted as urine, bile, or faeces.

Aristotle的《动物的各部分》详细阐述了他关于新陈代谢的观点，以便建立一个开放性的流动模型。他认为，在这个过程的每个阶段，来自食物的物质都会发生转化，释放出的热量成为火的典型元素，残余物质以尿液、胆汁或粪便的形式排出体外<ref>{{cite book|author=Leroi, Armand Marie|url=https://archive.org/stream/lagoonhowaristot0000lero?ref=ol#page/402/mode/2up|title=The Lagoon: How Aristotle Invented Science|date=2014|publisher=Bloomsbury|isbn=978-1-4088-3622-4|location=|pages=400–401|authorlink=Armand Marie Leroi}}</ref>。

===Islamic medicine===
伊斯兰医学
[[Ibn al-Nafis]] described metabolism in his 1260 AD work titled [[Al-Risalah al-Kamiliyyah fil Siera al-Nabawiyyah]] (The Treatise of Kamil on the Prophet's Biography) which included the following phrase "Both the body and its parts are in a continuous state of dissolution and nourishment, so they are inevitably undergoing permanent change."

Ibn al-Nafis described metabolism in his 1260 AD work titled Al-Risalah al-Kamiliyyah fil Siera al-Nabawiyyah (The Treatise of Kamil on the Prophet's Biography) which included the following phrase "Both the body and its parts are in a continuous state of dissolution and nourishment, so they are inevitably undergoing permanent change."

伊本·纳菲斯 Ibn al-Nafis 在其公元1260年的著作《 Al-Risalah al-Kamiliyyah fil Siera al-Nabawiyyah 》(《卡米尔关于先知传记的论述》)中描述了新陈代谢，其中包括以下短语: ”身体及其部分处于持续的溶解和营养状态，因此它们不可避免地要经历永久性的变化<ref>{{cite conference | vauthors = Al-Roubi AS | date = 1982 | title = Ibn Al-Nafis as a philosopher | conference = Symposium on Ibn al-Nafis, Second International Conference on Islamic Medicine | publisher = Islamic Medical Organization | location = Kuwait }} (cf. Ibn al-Nafis As a Philosopher, Encyclopedia of Islamic World [1])</ref>。

===Application of the scientific method===
科学方法的应用
The history of the scientific study of metabolism spans several centuries and has moved from examining whole animals in early studies, to examining individual metabolic reactions in modern biochemistry. The first controlled [[experiment]]s in human metabolism were published by [[Santorio Santorio]] in 1614 in his book ''Ars de statica medicina''. He described how he weighed himself before and after eating, [[sleeping|sleep]], working, sex, fasting, drinking, and excreting. He found that most of the food he took in was lost through what he called "[[insensible perspiration]]".

The history of the scientific study of metabolism spans several centuries and has moved from examining whole animals in early studies, to examining individual metabolic reactions in modern biochemistry. The first controlled experiments in human metabolism were published by Santorio Santorio in 1614 in his book Ars de statica medicina. He described how he weighed himself before and after eating, sleep, working, sex, fasting, drinking, and excreting. He found that most of the food he took in was lost through what he called "insensible perspiration".

新陈代谢的科学研究历史跨越了几个世纪，从早期研究中对动物整体的研究，到现代生物化学中对单个代谢反应的研究。人类新陈代谢的第一个对照实验是由圣托里奥·桑托里奥 Santorio Santorio于1614年在他的著作《静态医学》中发表的<ref>{{cite journal | vauthors = Eknoyan G | title = Santorio Sanctorius (1561-1636) - founding father of metabolic balance studies | journal = American Journal of Nephrology | volume = 19 | issue = 2 | pages = 226–33 | year = 1999 | pmid = 10213823 | doi = 10.1159/000013455 | s2cid = 32900603 }}</ref>。他描述了自己在进食、睡觉、工作、性交、禁食、饮水和排泄前后的体重。他发现他摄入的大部分食物都是通过他所谓的“无知觉的汗液”流失的。

[[File:SantoriosMeal.jpg|thumb|right|upright=0.7|Santorio Santorio 在他的杆秤上，来自静态医学，1614年首次发表]]

In these early studies, the mechanisms of these metabolic processes had not been identified and a [[vitalism|vital force]] was thought to animate living tissue. In the 19th century, when studying the [[fermentation (food)|fermentation]] of sugar to [[ethanol|alcohol]] by [[yeast]], [[Louis Pasteur]] concluded that fermentation was catalyzed by substances within the yeast cells he called "ferments". He wrote that "alcoholic fermentation is an act correlated with the life and organization of the yeast cells, not with the death or putrefaction of the cells." This discovery, along with the publication by [[Friedrich Woehler|Friedrich Wöhler]] in 1828 of a paper on the chemical synthesis of [[urea]], and is notable for being the first organic compound prepared from wholly inorganic precursors. This proved that the organic compounds and chemical reactions found in cells were no different in principle than any other part of chemistry.

In these early studies, the mechanisms of these metabolic processes had not been identified and a vital force was thought to animate living tissue. In the 19th century, when studying the fermentation of sugar to alcohol by yeast, Louis Pasteur concluded that fermentation was catalyzed by substances within the yeast cells he called "ferments". He wrote that "alcoholic fermentation is an act correlated with the life and organization of the yeast cells, not with the death or putrefaction of the cells." This discovery, along with the publication by Friedrich Wöhler in 1828 of a paper on the chemical synthesis of urea, and is notable for being the first organic compound prepared from wholly inorganic precursors. This proved that the organic compounds and chemical reactions found in cells were no different in principle than any other part of chemistry.

在早期的研究中，这些新陈代谢过程的机制还没有确定，人们认为一种生命力量是生命组织的活力<ref>{{cite book|url=https://archive.org/details/historyofscience04willuoft/page/n7/mode/2up|title=Modern Development of the Chemical and Biological Sciences|vauthors=Williams HA|date=1904|publisher=Harper and Brothers|isbn=|series=A History of Science: in Five Volumes|volume=IV|location=New York|pages=184–185|access-date=26 March 2007}}</ref>。19世纪，路易-巴斯德Louis Pasteur 在研究酵母菌将糖发酵成酒精时，得出结论：发酵是由酵母细胞内的物质催化的，他称之为 "发酵物"。他写道："酒精发酵是与酵母细胞的生命和组织有关的行为，而与细胞的死亡或腐烂无关"。这一发现<ref>{{cite journal | vauthors = Manchester KL | title = Louis Pasteur (1822-1895)--chance and the prepared mind | journal = Trends in Biotechnology | volume = 13 | issue = 12 | pages = 511–5 | date = December 1995 | pmid = 8595136 | doi = 10.1016/S0167-7799(00)89014-9 }}</ref>连同1828年弗里德里希-沃勒Friedrich Wöhler 发表的一篇关于尿素化学合成的论文<ref>{{cite journal | vauthors = Kinne-Saffran E, Kinne RK | title = Vitalism and synthesis of urea. From Friedrich Wöhler to Hans A. Krebs | journal = American Journal of Nephrology | volume = 19 | issue = 2 | pages = 290–4 | year = 1999 | pmid = 10213830 | doi = 10.1159/000013463 | s2cid = 71727190 }}</ref>，因为是第一个完全由无机前体制备的有机化合物而引人注目。这证明了在细胞中发现的有机化合物和化学反应与化学的任何其他部分在原理上没有什么不同。

It was the discovery of [[enzyme]]s at the beginning of the 20th century by [[Eduard Buchner]] that separated the study of the chemical reactions of metabolism from the biological study of cells, and marked the beginnings of [[biochemistry]]. The mass of biochemical knowledge grew rapidly throughout the early 20th century. One of the most prolific of these modern biochemists was [[Hans Adolf Krebs|Hans Krebs]] who made huge contributions to the study of metabolism. He discovered the urea cycle and later, working with [[Hans Kornberg]], the citric acid cycle and the glyoxylate cycle. Modern biochemical research has been greatly aided by the development of new techniques such as [[chromatography]], [[X-ray diffraction]], [[NMR spectroscopy]], [[radioisotopic labelling]], [[electron microscope|electron microscopy]] and [[molecular dynamics]] simulations. These techniques have allowed the discovery and detailed analysis of the many molecules and metabolic pathways in cells.

It was the discovery of enzymes at the beginning of the 20th century by Eduard Buchner that separated the study of the chemical reactions of metabolism from the biological study of cells, and marked the beginnings of biochemistry. The mass of biochemical knowledge grew rapidly throughout the early 20th century. One of the most prolific of these modern biochemists was Hans Krebs who made huge contributions to the study of metabolism. He discovered the urea cycle and later, working with Hans Kornberg, the citric acid cycle and the glyoxylate cycle. Modern biochemical research has been greatly aided by the development of new techniques such as chromatography, X-ray diffraction, NMR spectroscopy, radioisotopic labelling, electron microscopy and molecular dynamics simulations. These techniques have allowed the discovery and detailed analysis of the many molecules and metabolic pathways in cells.

爱德华·布赫纳（Eduard Buchner）在20世纪初发现了酶，从而将新陈代谢的化学反应研究与细胞的生物学研究分离开来，这标志着生物化学的开始<ref>Eduard Buchner's 1907 [http://nobelprize.org/nobel_prizes/chemistry/laureates/1907/buchner-lecture.html Nobel lecture] at http://nobelprize.org Accessed 20 March 2007</ref>。整个20世纪早期，生物化学知识的总量迅速增长。汉斯·克雷布斯（Hans Krebs）是这些现代生物化学家中最多产的一位，他对新陈代谢的研究做出了巨大的贡献。他发现了尿素循环<ref>{{cite journal | vauthors = Kornberg H | title = Krebs and his trinity of cycles | journal = Nature Reviews. Molecular Cell Biology | volume = 1 | issue = 3 | pages = 225–8 | date = December 2000 | pmid = 11252898 | doi = 10.1038/35043073 | s2cid = 28092593 }}</ref>，后来又与汉斯·科恩伯格（Hans Kornberg）合作，发现了三羧酸循环和乙醛酸循环。色谱、x射线衍射、核磁共振光谱、放射性同位素标记、电子显微镜和分子动力学模拟等新技术的发展极大地助力了现代生化研究<ref>{{cite journal |vauthors=Krebs HA, Henseleit K |title=Untersuchungen über die Harnstoffbildung im tierkorper |journal=Z. Physiol. Chem. |volume=210 |issue=1–2 |pages=33–66 |year=1932 |doi=10.1515/bchm2.1932.210.1-2.33}} 
{{cite journal | vauthors = Krebs HA, Johnson WA | title = Metabolism of ketonic acids in animal tissues | journal = The Biochemical Journal | volume = 31 | issue = 4 | pages = 645–60 | date = April 1937 | pmid = 16746382 | pmc = 1266984 | doi = 10.1042/bj0310645 }}</ref><ref name=Kornberg/>。这些技术已经能够发现和详细分析细胞中的许多分子和代谢途径。

== See also ==
另请参见

{{Portal|Metabolism}}新陈代谢

* {{anli|Anthropogenic metabolism}}人类新陈代谢

* {{anli|Antimetabolite}}抗代谢物

* {{anli|Basal metabolic rate}}基础代谢率

* {{anli|Calorimetry}}量热学

* {{anli|Isothermal microcalorimetry}}等温微量热法

* {{anli|Inborn errors of metabolism}}先天性代谢缺陷

* {{anli|Iron–sulfur world hypothesis}}, Hypothetical scenario for the origin of life, ，a "metabolism first" theory of the [[origin of life]] 铁硫世界假说，生命起源的假想情景，一个"新陈代谢第一 "的生命起源理论
* {{anli|Metabolic disorder}}代谢紊乱
* [[Microphysiometry]]微观生理学
* {{anli|Primary nutritional groups}}主要营养组织
* {{annotated link|Respirometry}}呼吸测量法
* {{anli|Stream metabolism}}流代谢
* {{anli|Sulfur metabolism}}硫代谢
* {{anli|Specific dynamic action|Thermic effect of food}}食物的热效应
* {{anli|Urban metabolism}}城市代谢
* {{anli|Fluid balance|Water metabolism}}水代谢平衡
* {{anli|Overflow metabolism}}溢出代谢
* {{anli|Reactome}} Reactome –生物途径数据库
* {{anli|KEGG}} 京都基因与基因组百科全书(Kyoto Encyclopedia of Genes and Genomes)

== References ==

{{Reflist|30em}}

== Further reading ==

{{Library resources box

|onlinebooks=yes

|by=no

|lcheading=Metabolism

|label=Metabolism

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'''Introductory'''

{{refbegin}}

* {{cite book | vauthors = Rose S, Mileusnic R | title = The Chemistry of Life. | publisher = Penguin Press Science | date = 1999 | isbn = 0-14-027273-9 }}

* {{cite book | vauthors = Schneider EC, Sagan D | title = Into the Cool: Energy Flow, Thermodynamics, and Life. | publisher = University of Chicago Press | date = 2005 | isbn = 0-226-73936-8}}

* {{cite book | vauthors = Lane N | title = Oxygen: The Molecule that Made the World. | publisher = Oxford University Press | location= USA | date = 2004 | isbn = 0-19-860783-0 }}

{{refend}}

General information

一般资料

'''Advanced'''

{{refbegin}}

* {{cite book | vauthors = Price N, Stevens L | title = Fundamentals of Enzymology: Cell and Molecular Biology of Catalytic Proteins. | publisher = Oxford University Press | date = 1999 | isbn = 0-19-850229-X }}

* {{cite book | vauthors = Berg J, Tymoczko J, Stryer L | title = Biochemistry | publisher = W. H. Freeman and Company | date = 2002 | isbn = 0-7167-4955-6 }}

* {{cite book | vauthors = Cox M, Nelson DL | title = Lehninger Principles of Biochemistry. | publisher = Palgrave Macmillan | date = 2004 | isbn = 0-7167-4339-6 }}

Human metabolism

人体新陈代谢

* {{cite book | author-link1 = Thomas D. Brock | vauthors = Brock TD, Madigan MR, Martinko J, Parker J | title = Brock's Biology of Microorganisms. | publisher = Benjamin Cummings | date = 2002 | isbn = 0-13-066271-2 }}

* {{cite book | vauthors = Da Silva JJ, Williams RJ | title = The Biological Chemistry of the Elements: The Inorganic Chemistry of Life. | publisher = Clarendon Press | date = 1991 | isbn = 0-19-855598-9 }}

* {{cite book | vauthors = Nicholls DG, Ferguson SJ | title = Bioenergetics | publisher = Academic Press Inc. | date = 2002 | isbn = 0-12-518121-3 }}

* {{cite journal | vauthors = Wood HG | title = Life with CO or CO2 and H2 as a source of carbon and energy | journal = FASEB Journal | volume = 5 | issue = 2 | pages = 156–63 | date = February 1991 | pmid = 1900793 | doi = 10.1096/fasebj.5.2.1900793 | s2cid = 45967404 }}

Databases

数据库

{{refend}}

== External links ==

{{Wikiversity|Topic:Biochemistry}}

{{wikibooks}}

Metabolic pathways

代谢途径

{{Wiktionary}}

{{Commons category}}

'''General information'''

* {{Britannica|377325|Metabolism (biology)}}

* [https://web.archive.org/web/20050308172226/http://www.rpi.edu/dept/bcbp/molbiochem/MBWeb/mb1/MB1index.html The Biochemistry of Metabolism]

* [http://www.sparknotes.com/testprep/books/sat2/biology/ Sparknotes SAT biochemistry] Overview of biochemistry. School level.

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* [http://www.sciencegateway.org/resources/biologytext/index.html MIT Biology Hypertextbook] Undergraduate-level guide to molecular biology.

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'''Human metabolism'''

* [http://library.med.utah.edu/NetBiochem/titles.htm Topics in Medical Biochemistry] Guide to human metabolic pathways. School level.

* [http://themedicalbiochemistrypage.org/ THE Medical Biochemistry Page] Comprehensive resource on human metabolism.

'''Databases'''

* [http://www.expasy.org/cgi-bin/show_thumbnails.pl Flow Chart of Metabolic Pathways] at [[ExPASy]]

* [http://www.iubmb-nicholson.org/pdf/MetabolicPathways_6_17_04_.pdf IUBMB-Nicholson Metabolic Pathways Chart]

* [http://bioinformatics.charite.de/supercyp/ SuperCYP: Database for Drug-Cytochrome-Metabolism]

'''Metabolic pathways'''

* [http://www.genome.ad.jp/kegg/pathway/map/map01100.html Metabolism reference Pathway]

* {{webarchive |url=https://web.archive.org/web/*/helios.bto.ed.ac.uk/bto/microbes/nitrogen.htm |date=* |title=The Nitrogen cycle and Nitrogen fixation }}

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{{Glycolysis enzymes}}

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{{Glycosaminoglycan metabolism enzymes}}

{{Glycoprotein metabolism enzymes}}

{{Glycolipid/sphingolipid metabolism enzymes}}

Category:Underwater diving physiology

类别: 水下潜水生理学

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This page was moved from [[wikipedia:en:Metabolism]]. Its edit history can be viewed at [[新陈代谢/edithistory]]</noinclude>

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