During which phase of cellular respiration is the majority of ATP produced?

The Electron Transport Chain is the phase of cellular respiration where the majority of ATP is produced, and this occurs in the inner mitochondrial membrane of eukaryotic cells. During this stage, electrons from NADH and FADH2, produced in earlier stages like glycolysis and the Krebs Cycle, are transferred through a series of protein complexes. This electron transport process creates a proton gradient across the inner mitochondrial membrane.

As protons flow back into the mitochondrial matrix through ATP synthase, the energy from this movement drives the phosphorylation of ADP to form ATP, a process known as chemiosmosis. This is highly efficient, often producing around 25-28 ATP molecules per glucose molecule, which is significantly more than the ATP generated during glycolysis and the Krebs Cycle. This mechanism underscores the importance of the Electron Transport Chain in maximizing the energy yield from glucose metabolism.