After glycolysis the pyruvate is converted to acetyl CoA and looses one carbon dioxide in the process. Two carbons enter the Krebs cycle as the fragments of the "A" in the Acetyl Co"A" and loose two carbon dioxide molecules in e process. Then energy is restocked through electron transfer between NOD+ and FAD. These carriers relay their cargo to the electron transport system which powers ATP synthesis. The Krebs cycle generates one ATP per revolution.
