Anaerobic glycolysis is a metabolic process in which glucose is transformed to lactate. The process occurs when energy is required in the absence of oxygen. Anaerobic glycolysis is essential for tissues with insufficient oxygen supply and high-energy requirements.
When the energy requirement of a certain cellular activity is not adequately met through aerobic glycolysis, the muscle cells process glucose in order to produce extra energy. During the process of anaerobic glycolysis, pyruvate is converted to lactate by the enzyme lactate dehydrogenase. The conversion of pyruvate to lactate provides the cells with a mechanism for the oxidation of NADH to NAD+, which is necessary for glycolysis.
Excess lactate is transported out of the cell and passes to the liver, where it is converted back into glucose in the presence of oxygen. Glucose is then capable of passing back to the peripheral cells in order to re-enter glycolysis. The process of converting glucose to lactate and lactate to glucose is known as the Cori cycle.
When the anaerobic process is prolonged, it leads to the formation of lactic acid, which decreases the pH of the blood. In order to avoid this, the process usually stops when the cell returns to normal oxygen levels.