The Krebs cycle uses acetyl-CoA as the starting substrate to produce NADH. During the cycle, acetyl-CoA combines with oxaloacetate to form citric acid, which undergoes a series of enzymatic reactions. In these reactions, NAD+ is reduced to NADH at three distinct steps, capturing high-energy electrons from the oxidation of intermediates in the cycle. Specifically, three molecules of NADH are generated per turn of the Krebs cycle from the oxidation of substrates derived from acetyl-CoA

. In summary, the Krebs cycle uses acetyl-CoA and NAD+ to produce NADH, along with other products such as FADH2, GTP (or ATP), and carbon dioxide. The NADH formed carries electrons to the electron transport chain for further energy production