Oxidative phosphorylation is the final stage of cellular respiration, in which the energy-rich molecules NADH and FADH2 generated from earlier stages are used to create a proton gradient across the inner mitochondrial membrane. The energy stored in this gradient is then used to generate ATP, the energy currency of the cell.
The process of oxidative phosphorylation takes place in the inner mitochondrial membrane, which is impermeable to ions and small molecules. The energy stored in the proton gradient is used to power the ATP synthase enzyme, which synthesizes ATP from ADP and inorganic phosphate. The ATP synthase is a complex of several subunits, and it uses the energy from the proton gradient to rotate a rotor subunit, which drives the synthesis of ATP.
The electron transport chain is the series of protein complexes that create the proton gradient. Electrons from NADH and FADH2 are passed along the chain, and at each complex, some of the energy is used to pump protons across the inner mitochondrial membrane. The final electron acceptor is oxygen, which combines with protons to form water.
The process of oxidative phosphorylation is highly efficient, and can generate up to 34 ATP molecules per glucose molecule in aerobic organisms. However, it is also sensitive to various factors, such as the availability of oxygen and the presence of inhibitors such as cyanide or carbon monoxide. Dysfunction in oxidative phosphorylation can lead to various diseases, such as mitochondrial disorders and metabolic diseases.