Metabolism pertains to all the chemical reactions involved in modifying a molecule into another. It may be categorized into two: catabolism and anabolism. Anabolism pertains to a sequence of chemical reactions that constructs or synthesizes molecules from smaller units, and usually these reactions require input of energy. Many of these reactions are fueled through the hydrolysis of ATP. In contrast, catabolism includes a series of degradative chemical reactions that break down complex molecules into smaller units, and often they release energy in the process. These processes are regulated by circadian rhythms. Anabolism is for the synthesis of complex molecules essential in building up of organs and tissues. It is therefore responsible for the increase in body size. Examples of anabolism are bone growth and mineralization, and muscle mass build-up. Hormones are typically classified as either anabolic (pertaining to anabolism) or catabolic (pertaining to catabolism) based on their effect on the metabolic processes.
Word origin: Greek anabole ("to build up")
- constructive metabolism