Oxidative phosphorylation is a crucial metabolic process that occurs in the mitochondria of cells. It involves the transfer of electrons through a series of proteins known as the electron transport chain. As electrons move along this chain, they release energy, which is used to pump protons across the mitochondrial membrane, creating a proton gradient. This gradient drives the synthesis of adenosine triphosphate (ATP) through an enzyme called ATP synthase. The final step of oxidative phosphorylation involves the reduction of molecular oxygen, which combines with electrons and protons to form water. This process is essential for producing the energy needed for various cellular functions.