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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).

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’’’<font color=’’#ff8000’’>化学反应 chemical reaction</font>’’’。新陈代谢的三个主要目的是：将食物转化为能量以进行细胞处理；将食物/燃料转化为’’’<font color=’’#ff8000’’> 蛋白质proteins</font>’’’、’’’<font color=’’#ff8000’’> 脂类lipids</font>’’’、’’’<font color=’’#ff8000’’> 核酸 nucleic acids</font>’’’和一些’’’<font color=’’#ff8000’’>碳水化合物carbohydrates </font>’’’的构件；以及消除’’’<font color=’’#ff8000’’> 代谢废物 metabolic wastes</font>’’’。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，包括消化和物质在不同细胞内和细胞之间的运输，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间代谢）。

新陈代谢（/məˈtæbəlɪzəm/，来自希腊语：μεταβολή metabolē，"变化"）是生物体内维持生命的’’’<font color=’’#ff8000’’>化学反应 chemical reaction</font>’’’。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’’’<font color=’’#ff8000’’> 蛋白质proteins</font>’’’、’’’<font color=’’#ff8000’’> 脂类lipids</font>’’’、’’’<font color=’’#ff8000’’> 核酸 nucleic acids</font>’’’和一些’’’<font color=’’#ff8000’’>碳水化合物carbohydrates </font>’’’的构件；以及消除’’’<font color=’’#ff8000’’> 代谢废物 metabolic wastes</font>’’’。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'' ([[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.

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’’’<font color=’’#ff8000’’> 分解代谢catabolic </font>’’’分解代谢-分解化合物(例如，通过’’’<font color=’’#ff8000’’>细胞呼吸 cellular respiration</font>’’’将葡萄糖分解为丙酮酸) ; 或合成-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’’’<font color=’’#ff8000’’> 分解代谢catabolic </font>’’’分解代谢-分解化合物(例如，通过’’’<font color=’’#ff8000’’>细胞呼吸 cellular respiration</font>’’’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 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.

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’’’<font color=’’#ff8000’’>酶 enzyme </font>’’’来促进。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。

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’’’<font color=’’#ff8000’’>酶 enzyme </font>’’’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 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.

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’’’<font color=’’#ff8000’’> 原核生物prokaryotes</font>’’’利用硫化氢作为营养物质，然而这种气体对动物是有毒的。生物体的’’’<font color=’’#ff8000’’>基础代谢率basal metabolic rate  </font>’’’是衡量所有这些化学反应所消耗的能量。

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’’’<font color=’’#ff8000’’> 原核生物prokaryotes</font>’’’利用硫化氢作为营养物质，然而这种气体对动物是有毒的。生物体的’’’<font color=’’#ff8000’’>基础代谢率basal metabolic rate  </font>’’’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 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.

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。例如，作为’’’<font color=’’#ff8000’’>三羧酸循环 citric acid cycle</font>’’’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，在单细胞细菌’’’<font color=’’#ff8000’’>大肠杆菌 Escherichia coli</font>’’’和巨大的多细胞生物（如大象）中都能找到。 这些代谢途径的相似性很可能是由于它们在进化史上的早期出现，又因为它们的功效而保留下来。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。

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。例如，作为’’’<font color=’’#ff8000’’>三羧酸循环 citric acid cycle</font>’’’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’’’<font color=’’#ff8000’’>大肠杆菌 Escherichia coli</font>’’’和巨大的多细胞生物（如大象）中都能被找到。 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。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。

This is a diagram depicting a large set of human metabolic pathways.

This is a diagram depicting a large set of human metabolic pathways.

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.<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>

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.<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>