A complex series of cellular biochemical reactions, not requiring oxygen, that splits glucose, glycogen or other carbohydrates into pyruvic or lactic, acid while storing energy in ATP molecules.

One molecule of glucose undergoes two phosphorylation reactions and is then splits to form two triose-phosphate molecules. Each of these is converted to pyruvate. The net energy yield is two ATP molecules per glucose molecule.

In aerobic respiration pyruvate then enters the Krebs cycle. Alternatively, when oxygen is in short supply or absent, the pyruvate is converted to various products by anaerobic respiration.

Other simple sugars, e.g fructose and galactose and glycerol enter the glycolysis pathway at intermediate stages.