Oxidative phosphorylation is a metabolic pathway in which the energy produced by the oxidation of nutrients is stored in the mitochondria in the form of ATP. Almost all aerobic organisms carry out oxidative phosphorylation. Oxidative phosphorylation is associated with the transfer of electrons from donor compounds to acceptor compounds during redox reactions. The movement of electrons through the electron transport chain (ETC) is used to transfer protons through the inner mitochondrial membrane into the intermembrane space. The process results in the accumulation of the potential energy composed of a proton gradient and an electric potential that are used by ATP synthase to synthesize ATP from ADP during the phosphorylation reaction. The oxidative phosphorylation is a crucial metabolic process that results in the formation of ATP. There are several well-known biologically active substances and toxins that inhibit oxidative phosphorylation and lead to death. Examples include cyanides that inhibit ETC by binding to the Fe-Cu center in cytochrome c-oxidase, 2,4-dinitrophenol that destroys the proton gradient and other inhibitors. The oxidative phosphorylation also results in the release of heat in adipocytes involved in the thermoregulatory processes.