CHEMIOSMOSIS
The production of ATP from ADP is coupled to the transfer of electrons in the electron transport chain. The chemiosmotic model has been proposed to explain how ATP synthesis is coupled to electron transport. Some of the energy released as electrons pass along the electron transport chain is used to pump protons (hydrogen ions) across the inner mitochondrial membrane from the matrix into the intermembrane space (see figure). The accumulation of protons is a form of potential energy that can be used to synthesize ATP.

As the accumulated protons diffuse back through the transmembrane protein ATP synthase, it catalyzes the phosphorylation of ADP, forming ATP. A maximum of 32 to 34 ATPs are produced during electron transport and chemiosmosis associated with a single glucose molecule.