Photo by Malcolm Johnson

The citric acid cycle (CAC), also known as the Krebs cycle was formally identified by Sir Hans Krebs and William Arthur Johnson at the University of Sheffield in 1937.

The cycle is a key process inside a cell, connecting carbohydrate, fat and protein metabolism. It describes a series of chemical reactions used by all aerobic organisms: the release of stored energy through the oxidation of a molecule called acetyl-

CoA derived from carbohydrates, fats, and proteins, into a compound called adenosine triphosphate (ATP) and carbon dioxide.

The cycle’s central importance in many biochemical pathways suggests that it was one of the earliest established components of cellular metabolism and may date back to the origins of life.