The citric acid cycle is a series of chemical reactions whereby acetate molecules from food are broken down into carbon dioxide, water and energy. It is the principal method by which all aerobic organisms generate energy.
During the citric acid cycle, acetate derived from carbohydrates, proteins and fats is oxidized in a step-by-step process that yields ATP, or adenosine triphosphate, the molecule that transports the chemical energy that cells need for metabolism. In plants and animals, this series of reactions take place in the mitochondria of the cell. Sometimes called the Krebs cycle, the citric acid cycle was discovered by Sir Hans Adolf Krebs, a British biochemist, in 1937.