The citric acid cycle (a.k.a. tricarboxylic acid [TCA] cycle or Krebs cycle, for Hans Adolph Krebs who identified it in 1937) is a series of biochemical reactions used by all aerobic organisms to produce energy from carbohydrates, protein, and fat. This occurs through the oxidation of acetyl-CoA, leading to ATP production. In contrast to glycolysis, the citric acid cycle occurs in mitochondria.