Final answer:
The energy stored in a proton gradient is used to produce ATP from ADP and Pi during oxidative phosphorylation, involving an electron transport chain and an enzyme called ATP synthase in chemiosmosis.
Step-by-step explanation:
The energy stored in a proton gradient is used to synthesize ATP from ADP and Pi during the process of oxidative phosphorylation. This crucial step in cellular respiration involves the transfer of electrons down the electron transport chain, which in turn pumps protons across the mitochondrial membrane, creating an electrochemical gradient. ATP synthase, a key enzyme, harnesses this gradient, allowing protons to flow back into the mitochondrial matrix, and this flow drives the synthesis of ATP. During chemiosmosis, as protons move through ATP synthase, the enzyme rotates, facilitating the phosphorylation of ADP into ATP. Oxidative phosphorylation is the most efficient way of producing ATP in aerobic organisms and takes place in the mitochondria of eukaryotic cells or the plasma membrane of prokaryotic cells.