Define oxidative phosphorylation.

Oxidative phosphorylation is a crucial metabolic process in cellular respiration that takes place in the mitochondria. It specifically involves the electron transport chain and chemiosmosis to generate ATP, the primary energy currency of the cell. During oxidative phosphorylation, electrons are transferred through a series of protein complexes in the inner mitochondrial membrane. As electrons move through these complexes, they release energy, which is utilized to pump protons (H⁺ ions) from the mitochondrial matrix into the intermembrane space, creating a proton gradient.

The energy stored in this proton gradient generates a potential energy source, and when protons flow back into the matrix through the enzyme ATP synthase, ATP is produced. This efficient coupling of electron transport and ATP synthesis defines oxidative phosphorylation, making it a vital component of the overall process of cellular respiration. The high yield of ATP produced through this mechanism is essential for the energy needs of aerobic organisms.