代谢(metabolism)
现生生物每个细胞内发生的化学反应总和，供应生命所需能量并合成新的细胞物质。「中间代谢」论及庞大网状的互相联系的化学反应，藉此产生或消灭所有细胞的组成，许多成分在细胞外面极为罕见。同化反应（合成代谢作用）利用能量从较简单的有机化合物建造复杂的分子（如氨基酸变成蛋白质，糖变成碳水化合物，脂肪酸和丙三醇变成脂肪）；异化反应（分解代谢作用）将复杂的分子分解成较简单的分子，释放出化学能。对大多数生物而言，能量总归是来自太阳，不管是由光合作用取得储存在有机化合物之间，或是吃这些光合作用的生物消耗其储存的有机化合物。有些特殊环境的细菌，例如在深海裂口，能量是由化学键结。在细胞内或生物体内，能量是由三磷酸腺来传递；同化反应消耗三磷酸腺，异化作用则生成。每个细胞化学反应是由特定的居间协调。物质分解作用通常是不可逆的作用，因此需要不同的。亦请参阅digestion、fermentation、tricarboxylic acid cycle。
English version：
metabolism
Sum of all the chemical reactions that take place in every cell of a living organism, providing energy for the processes of life and synthesizing new cellular material. “Intermediary metabolism” refers to the vast web of interconnected chemical reactions by which all the cell's constituents, many rarely found outside it, are created and destroyed. Anabolic reactions use energy to build complex molecules from simpler organic compounds (e.g., proteins from amino acids, carbohydrates from sugars, fats from fatty acids and glycerol); catabolic reactions break complex molecules down into simpler ones, releasing chemical energy. For most organisms, the energy comes ultimately from the sun, whether they obtain it by photosynthesis and store it in organic compounds or consume those that photosynthesize for the energy stored in their organic compounds. In some bacteria in special environments such as deep-sea vents, the energy comes from chemical bonds instead. Energy is transferred within the cell and the organism by ATP; anabolic reactions consume it, and catabolic reactions generate it. Every cellular chemical reaction is mediated by a specific enzyme. The process that breaks down a substance is not usually the reverse of the process that makes it and uses a different enzyme. See also digestion, fermentation, tricarboxylic acid cycle.