The Krebs cycle produces two molecules of ATP for every molecule of glucose. The Krebs cycle also produces eight molecules of NADH and two molecules of FADH2 per molecule of glucose. NADH and FADH2 are later used to produce energy during electron transport phosphorylation.
During the process of aerobic respiration, one molecule of glucose is first broken down into two molecules of pyruvate. Before entering the Krebs cycle, the pyruvate is modified into acetyl coenzyme A. The acetyl-CoA is first combined with molecules already in the Krebs cycle and then undergoes a series of energy-releasing reactions. The remaining molecule is then combined with a new acetyl-CoA, restarting the cycle.