The citric acid cycle (TCA cycle) is a series of chemical reactions in the mitochondria that breaks down acetyl-CoA generated from carbohydrates, fats, and proteins into carbon dioxide and hydrogen to generate ATP. The cycle consists of 8 steps where acetyl-CoA condenses with oxaloacetate to form citrate, undergoing oxidation, decarboxylation and hydration reactions to regenerate oxaloacetate and produce NADH, FADH2, and GTP to fuel oxidative phosphorylation for ATP production. The TCA cycle plays a key role in cellular respiration and energy production.