Which phase of cellular respiration produces the most ATP?

Oxidative phosphorylation is the phase of cellular respiration responsible for producing the most ATP. This process occurs in the inner mitochondrial membrane, where the electron transport chain and ATP synthase are located. During oxidative phosphorylation, electrons are transferred through a series of protein complexes, which creates a proton gradient across the membrane. This gradient powers ATP synthase, an enzyme that synthesizes ATP from ADP and inorganic phosphate. The efficiency of this process allows for the generation of approximately 26 to 28 ATP molecules per glucose molecule, significantly more than the amounts produced in glycolysis and the Krebs cycle.

In contrast, glycolysis, while it does produce a net gain of 2 ATP and occurs in the cytoplasm, generates far less ATP overall. The Krebs cycle, also known as the citric acid cycle, occurs in the mitochondrial matrix and yields a small number of ATP, specifically 2 ATP per glucose molecule when considering the full cycle. Fermentation, on the other hand, is an anaerobic process that occurs in the absence of oxygen and produces even less ATP, typically only 2 ATP per glucose molecule, similar to glycolysis but without any further yield from the Krebs cycle or oxidative phosphorylation. Thus, oxidative phosphorylation stands out as the most efficient ATP-producing