Metabolism is the total set of chemical reactions that occur in living cells. These processes are the source of life, allowing cells to grow and reproduce, maintain their structures, and react to their environments. Metabolism is frequently divided into two categories. Catabolic reactions yield energy, an example being the stop working of food in cellular respiration. Anabolic reactions, on the other hand, use this energy to construct mechanism of cells such as proteins and nucleic acids.
The chemical reactions of metabolism are organized into metabolic pathways, in which one chemical is distorted into another by a series of enzymes. Enzymes are vital to metabolism because they allow cells to drive desirable but thermodynamically unfavorable reactions by combination them to favorable ones. Enzymes also agree to the regulation of metabolic pathways in response to changes in the cell's environment or signals from other cells.