During the breakdown of glucose, which stage produces the most energy?

The stage that produces the most energy during the breakdown of glucose is oxidative phosphorylation. This process occurs in the inner mitochondrial membrane and is the final stage of cellular respiration. During oxidative phosphorylation, electrons are transferred through a series of proteins known as the electron transport chain. This transfer of electrons creates a proton gradient across the mitochondrial membrane.

As protons flow back into the mitochondrial matrix through ATP synthase, a significant amount of ATP is generated. In fact, oxidative phosphorylation is responsible for producing the majority of ATP during cellular respiration, typically yielding about 26 to 28 molecules of ATP per molecule of glucose. This energy yield is considerably higher than that from glycolysis or the Krebs cycle.

Glycolysis, occurring in the cytoplasm, breaks down glucose into pyruvate and produces a net gain of only 2 ATP molecules per glucose molecule. The Krebs cycle, which takes place in the mitochondrial matrix, generates electron carriers like NADH and FADH2 that are used in oxidative phosphorylation but produces only 2 ATP molecules directly per glucose molecule as well. Fermentation, which occurs in the absence of oxygen, provides even less energy, yielding only 2 ATP without the further processing of pyruvate into acetyl-CoA and without involvement of