The process that produces the most ATP is oxidative phosphorylation, which takes place in the mitochondria during cellular respiration.
Oxidative phosphorylation is the final stage of aerobic respiration and it involves the electron transport chain and chemiosmosis. During this process, electrons from NADH and FADH2 are passed along a series of protein complexes in the inner mitochondrial membrane. As these electrons move through the chain, they release energy, which is used to pump protons (H+) across the membrane, creating a proton gradient.
When protons flow back into the mitochondrial matrix through ATP synthase, this enzyme utilizes the energy from the flow to convert ADP and inorganic phosphate (Pi) into ATP. This mechanism can produce approximately 26 to 28 ATP molecules for each glucose molecule metabolized, making it the most efficient way to generate energy in the form of ATP.
In summary, while other processes like glycolysis and the citric acid cycle also produce ATP, oxidative phosphorylation yields the highest amount, making it the most significant source of ATP in aerobic organisms.