Which stage of cellular respiration produces the most NADH?

The Krebs Cycle, also known as the citric acid cycle, is the stage of cellular respiration that produces the most NADH. During the Krebs Cycle, each acetyl CoA molecule that enters the cycle is oxidized, leading to the reduction of NAD+ to NADH. For each turn of the cycle, three molecules of NADH are generated, as well as one molecule of FADH2, and one molecule of ATP or GTP.

Given that each glucose molecule is broken down into two acetyl CoA molecules, the Krebs Cycle turns twice for each glucose molecule, resulting in a total of six NADH molecules produced per glucose molecule. This generation of NADH is crucial because NADH serves as an electron carrier, transporting electrons to the electron transport chain, where they contribute to ATP production.

In comparison, glycolysis produces only two NADH molecules per glucose molecule, while fermentation does not produce any NADH from glucose; it serves as an anaerobic pathway that regenerates NAD+ to allow glycolysis to continue without oxygen. The electron transport chain does not produce NADH; instead, it uses the NADH generated in earlier stages to facilitate ATP production.