The biochemical process of producing the energy that supports the activity of organisms is called metabolism, and the exchange of energy in living bodies is mainly mediated by ATP. Metabolism, in addition to its energetic aspect, also has a substance-metabolic aspect - the synthesis, degradation and interconversion of various biological materials. Enzymes in the form of biocatalysts are involved in cellular metabolism. They are normally made of proteins, and catalyze certain reactions by specifically binding to substrates. Cellular metabolism is a combination of metabolic pathways common to many organisms. To regulate metabolic activity and pathways in accordance with the physiological state of cells, allosteric regulation of enzymatic activity by metabolites and metabolic regulation by chemical modification occur in addition to the synthesis and degradation of enzymes.