更改

新陈代谢 (查看源代码)

2021年8月3日 (二) 20:41的版本

添加236字节、 2021年8月3日 (二) 20:41

无编辑摘要

第1行：第1行：

{{#seo:

|keywords=布莱恩大脑,元胞自动机

−

|description=~~布莱恩的大脑(Brain~~'s ~~brain)是由加拿大计算机科学家布莱恩·西尔弗曼~~ Brian Silverman设计的元胞自动机。其特点在于，规则模拟了大脑神经元之间的信息传递规则。

+

|description=布莱恩的大脑（Brain's brain）是由加拿大计算机科学家布莱恩·西尔弗曼 Brian Silverman设计的元胞自动机。其特点在于，规则模拟了大脑神经元之间的信息传递规则。

}}

第15行：第15行：

'''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）。

−

新陈代谢反应可分为分解代谢-~~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。~~

+

新陈代谢反应可分为分解代谢-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。

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。

第29行：第29行：

[[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。]]

−

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.|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>

+

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.|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 “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 || 氨基酸 ||~~蛋白质(由多肽组成)~~

+

| 氨基酸 || 氨基酸 ||蛋白质（由多肽组成）

|纤维蛋白和球状蛋白

|-

第46行：第46行：

===脂类 ===

−

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 | vauthors = Berg JM, Tymoczko JL, Gatto Jr GJ, Stryer L |date=8 April 2015|publisher=W. H. Freeman|pages=362}}</ref>。

+

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 | vauthors = Berg JM, Tymoczko JL, Gatto Jr GJ, Stryer L |date=8 April 2015|publisher=W. H. Freeman|pages=362}}</ref>。

===碳水化合物===

第62行：第62行：

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>。

−

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|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B~~3~~(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}}</ref>。

+

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|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}}</ref>。

[[File:1GZX Haemoglobin.png|thumb|upright=1.35|right|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。]]

===矿物质和辅因子===

−

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。

+

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。

丰富的无机元素可以电解质。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 }}</ref>。

第111行：第111行：

|}

−

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"/>。

+

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"/>。

===消化===

更多信息：消化和胃肠道

第117行：第117行：

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}}</ref>。

−

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 }}</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>。

+

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 }}</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|right|upright=1.35|蛋白质，碳水化合物和脂肪分解代谢的简化概述。 ]]

第130行：第130行：

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>。

−

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>。

+

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>。

==能量转换==

第136行：第136行：

更多信息：氧化磷酸化，化学渗透和线粒体

−

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>。

+

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。]]

−

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" />。

+

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" />。

===无机化合物的能量===

更多信息：微生物代谢和氮循环

−

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 }}</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>。

+

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 }}</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>。

===光能 ===

第152行：第152行：

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>。

−

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 }}</ref>。

+

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 }}</ref>。

−

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 }}</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。~~

+

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 }}</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。

==合成代谢==

第169行：第169行：

[[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。]]

−

~~光合作用就是依靠阳光和二氧化碳(CO~~2~~)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CO~~2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>。

+

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>。

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CO2 <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 }}</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>。

第178行：第178行：

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 }}</ref>。

−

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 }}</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 | 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.|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> 。

+

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 }}</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 | 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.|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> 。

−

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|access-date=2020-07-08|last2=Hart|first2=Gerald W.|last3=Schnaar|first3=Ronald L. |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 }}</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>。

+

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|access-date=2020-07-08|last2=Hart|first2=Gerald W.|last3=Schnaar|first3=Ronald L. |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 }}</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>。

===脂肪酸，类异戊二烯和固醇===

第197行：第197行：

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>。

−

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>。

+

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>。

===核苷酸的合成和补救途径 ===

更多信息：核苷酸补救途径，嘧啶的生物合成和嘌呤§代谢

−

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>。

+

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>。

==异种生物学和氧化还原代谢 ==

更多信息：异生物质代谢，药物代谢，酒精代谢和抗氧化剂

−

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 }}</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>

+

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 }}</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>

。

第215行：第215行：

更多信息：生物热力学

−

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>。

+

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>。

==调控 ==

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

−

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 | 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 }}</ref>。

+

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 | 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 }}</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）。]]

−

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>。

+

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>。

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>。

第237行：第237行：

]]

−

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 |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}}</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>。

+

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 |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}}</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>。

−

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>。

+

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>。

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 | bibcode = 2006Natur.440..667P }}</ref>。

第248行：第248行：

[[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。]]

−

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>。

+

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>。

−

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>。

+

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>。

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。

−

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 }}

+

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 }}</ref>。

第268行：第268行：

===伊斯兰医学 ===

−

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>。

+

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>。

===科学方法的应用 ===

−

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 }}</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。

+

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 }}</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。]]

−

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 }}</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。

+

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 }}</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。

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 }}</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}}

第306行：第306行：

* 溢出代谢

* 生物途径数据库

−

* ~~京都基因与基因组百科全书(Kyoto~~ Encyclopedia of Genes and ~~Genomes)~~

+

* 京都基因与基因组百科全书（Kyoto Encyclopedia of Genes and Genomes）

== 参考资料ferences ==

第388行：第388行：

'''General information'''

−

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

+

* {{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]

唐糖糖

1,068

个编辑

更改

新陈代谢 (查看源代码)

2021年8月3日 (二) 20:41的版本

导航菜单

搜索