同化作用，又称为合成代谢，是指生物体利用能量将小分子合成为大分子的一系列代谢途径。

Anabolism (from Greek: ἁνά "upward" and βάλλειν "to throw") is the set of metabolic pathways that construct molecules from smaller units. These reactions require energy. One way of categorizing metabolic processes, whether at the cellular, organ or organism level, is as "anabolic", or as "catabolic" which is the opposite. Anabolism is powered by catabolism, where large molecules are broken down into smaller parts and then used up in respiration. Many anabolic processes are powered by the hydrolysis of adenosine triphosphate (ATP).