oxidative phosphorylation

The mitochondrial oxidative phosphorylation (OXPHOS) system is the final biochemical pathway in the production of ATP.

In oxidative phosphorylation, the electrons removed from food molecules in pathways such as the citric acid cycle (Krebs cycle) are transferred to oxygen and the energy released is used to make ATP.

This is done in eukaryotes by a series of proteins in the membranes of mitochondria called the electron transport chain (oxidative phosphorylation chain or OXPHOS system). In prokaryotes, these proteins are found in the cell’s inner membrane.

These proteins use the energy released from passing electrons from reduced molecules like NADH onto oxygen to pump protons across a membrane.

Pumping protons out of the mitochondria creates a proton concentration difference across the membrane and generates an electrochemical gradient.

This force drives protons back into the mitochondrion through the base of an enzyme called ATP synthase. The flow of protons makes the stalk subunit rotate, causing the active site of the synthase domain to change shape and phosphorylate adenosine diphosphate (ADP), turning it into ATP.

See OXPHOS system