Citric acid cycle

The citric acid cycletricarboxylic acid cycle, the TCA cycle, the Krebs cycle, or Szent-Györgyi-Krebs cycle (after Hans Adolf Krebs and Albert Szent-Györgyi who first determined the chemical intermediates and reaction sequence of the cycle)] is a series of enzyme-catalysed chemical reactions of central importance in all living cells that use oxygen as part of cellular respiration. In aerobic organisms, the citric acid cycle is part of a metabolic pathway involved in the chemical conversion of carbohydrates, fats and proteins into carbon dioxide and water to generate a form of usable energy. It is the third of four metabolic pathways that are involved in carbohydrate catabolism and ATP production, the other three being glycolysis and pyruvate oxidation before it, and respiratory chain after it.

The citric acid cycle also provides precursors for many compounds such as certain amino acids, and some of its reactions are therefore important even in cells performing fermentation.