Need a plan to keep you on track?
Try the Study Plan Builder!
A key source of acetyl-CoA is from the pyruvate produced by glycolysis, which undergoes oxidative decarboxylation by pyruvate dehydrogenase (generating a 2-carbon group from a 3-carbon molecule, releasing CO2 and reducing NAD+ to NADH in the process). Other sources include transformation from amino acids and ketone bodies as well as beta-oxidation of fatty acids.
Acetyl-CoA interacts at the start of the citric acid cycle, transferring its 2-carbon acetyl group to the 4-carbon oxaloacetate to produce the 6-carbon citrate. One turn of the citric acid cycle takes this molecule through a series of oxidations, eventually recreating oxaloacetate to begin anew cycle, producing along the way: 3 NADH, 1 FADH2, 1 GTP, and the release of 2 CO2.
The citric acid cycle is regulated significantly by the availability of electron carriers NAD and FAD, thus requiring the presence of O2 to act as the final electron acceptor of the electron transport chain. Buildup of NADH will slow the reactions of the citric acid cycle.
Together glycolysis and the pyruvate dehydrogenase complex produce 2 net ATP and 4 NADH per glucose.
Each turn of the citric acid cycle produces 1 ATP (generated from GTP), 3 NADH, and 1 FADH2 (that is 2 ATP, 6 NADH, and 2 FADH2 per glucose, two turns of citric acid cycle).
Together, glycolysis, the conversion of pyruvate, and the citric acid cycle produce 4 ATP, 10 NADH, and 2 FADH2 per molecule of glucose. Oxidative phosphorylation via the electron transport chain then produces 4 + 30 + 4 = 38 ATP per glucose. Transport of NADH produced from glycolysis in the cytosol into the mitochondria in eukaryotes requires 1 ATP each, so the net ATP production becomes 36 ATP.
Learn more about planning and tracking your MCAT prep!
MCAT.me Tour →