ABSTRACT
Metabolism is defined as the sum of all chemical reactions that occur within a living cell. The purpose of cellular metabolism is to maintain the homeostasis of the cell within a population of other cells. Homeostasis refers to a tendency toward maintenance of a relatively stable internal environment in the bodies of higher animals through a series of interacting physiological processes. Metabolism is usually subdivided into two categories: anabolism and catabolism. Anabolism is the synthesis of larger molecules from smaller ones. The synthesis of a protein from its amino acid building blocks is an example. Anabolism generally requires input of energy from an energy source, such as ATP. Catabolism refers to the degradation of larger molecules to smaller ones, e.g., the breakdown of starch to glucose. In higher organisms, catabolism of carbohydrates and fats results in the production of ATP.
