Pasteur effect

Modification in the process of energy production in certain organisms. A bacterium or facultative cell which normally produces its ATP anaerobically, that is, without the use of oxygen, does so by means of glycolysis. In this process the yield of ATP per molecule of glucose is low, so the cell uses up a great deal of its glucose for its energy requirements. An aerobic organism, which uses oxygen, can employ the Krebs cycle to produce its energy, and the yield of ATP per molecule of glucose is much greater. The Pasteur effect occurs when a facultative anaerobic cell is provided with oxygen, so that its high rate of glucose metabolism is slowed down. It then produces energy from glucose far more efficiently because Krebs cycle is used, and in addition the production of lactic acid, a normal product of anaerobic glycolysis, is automatically stopped.