The Krebs cycle, also known as the citric acid cycle and the tricarboxylic acid cycle, is the central metabolic pathway that takes place in the mitochondrion and breaks down all metabolites, including sugars, fatty acids and amino acids. The cycle is named after German-born British physician and biochemist Hans Adolf Krebs, who identified the citric acid cycle in the human body while working at the University of Sheffield in 1937.
In recognition of the significance of this work, Krebs was awarded the Nobel Prize for Physiology or Medicine in 1953. The Krebs cycle uses eight different enzymes to transform acetyl-CoA (acetyl coenzyme A) into two molecules of carbon dioxide and one molecule of ATP (adenosine triphosphate). It is often conceived of as an aerobic process, which means that it requires oxygen, and breaks down glucose to convert it into ATP. However, this is not the case, as the Krebs cycle uses neither glucose nor oxygen. The Krebs cycle starts with a molecule of acetyl-CoA, which can be generated within the body by breaking down carbohydrates through the process of glycolysis and to engage fatty-acid metabolism. Within the body, the Krebs cycle is regulated by the inhibition of certain products and the availability of substrates. Because of this regulation of the Krebs cycle, the body prevents the waste of metabolic energy that would occur if the cycle were to run continuously.