During which stage of cellular respiration is the most ATP produced?

The stage of cellular respiration where the most ATP is produced is the electron transport chain. This process occurs in the inner mitochondrial membrane and involves a series of protein complexes that drive the production of ATP through oxidative phosphorylation. As electrons are transferred through these complexes, they create a proton gradient across the membrane. The flow of protons back into the mitochondrial matrix through ATP synthase generates a significant amount of ATP—typically around 26 to 28 ATP molecules per glucose molecule.

In comparison, glycolysis produces only a net gain of 2 ATP molecules, and the Krebs cycle contributes a modest amount of ATP directly, usually around 2 ATP molecules as well. Fermentation, while it allows for ATP production in anaerobic conditions, yields just 2 ATP per glucose molecule, similar to glycolysis, which is far less than what is produced in the electron transport chain. Hence, the electron transport chain is the most prolific stage in terms of ATP production during cellular respiration.