The central hub of aerobic metabolism
The Krebs cycle, also called the citric acid or TCA cycle, runs in the mitochondrial matrix. Acetyl-CoA, derived from carbohydrate, fat, and protein breakdown, combines with oxaloacetate to form citrate. A series of reactions then progressively oxidizes the carbons, releasing two molecules of carbon dioxide and regenerating oxaloacetate so the cycle can turn again.
What each turn yields
Per turn, the cycle produces three NADH, one FADH2, and one GTP (or ATP), plus the two CO2. The real value lies in the NADH and FADH2: these carry high-energy electrons to the electron transport chain, where most ATP is actually made. Because one glucose yields two acetyl-CoA, the cycle turns twice per glucose. The cycle also supplies intermediates for synthesizing amino acids and other molecules, making it a metabolic crossroads, not just an energy producer. General educational information about metabolism.