The Krebs Cycle
Before the pyruvates formed in glycolysis enter the Krebs Cycle, the body must have enough oxygen. If no oxygen is present, then fermentation occurs. Otherwise, the pyruvates undergo an intermediate step and enter the Krebs Cycle.
In the intermediate step, each pyruvate is attached to acetyl-CoA. Two NADH (one for each pyruvate) and a two molecules of carbon dioxide is formed.
Each pyruvate must pass through the Krebs Cycle. Through a series of reactions, 3 NADH and 2 FADH2 are formed. Multiplied by two for the two pyruvates, a total of 6 NADH and 4 FADH2 are formed. These products along with the 2 NADH formed in glycolysis enter the electron transport system.
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