Glycolysis: Metabolic pathway, Pyruvic acid, Thermodynamic free energy, Adenosine triphosphate, Nicotinamide adenine dinucleotide, Fructose, Galactose, Metabolism, Anaerobic respiration, Gustav Embden

Glycolysis is the metabolic pathway that converts glucose, C6H12O6, into pyruvate, C3H3O3-. The free energy released in this process is used to form the high energy compounds, ATP (adenosine triphosphate) and NADH (reduced nicotinamide adenine dinucleotide). Glycolysis is a sequence of ten reactions involving ten intermediate compounds (one of the steps involves two intermediates). The intermediates provide entry points to glycolysis. For example, most monosaccharides, such as fructose, glucose, and galactose, can be converted to one of these intermediates. The intermediates may also be directly useful. For example, the intermediate dihydroxyacetone phosphate is a source of the glycerol that combines with fatty acids to form fat. Glycolysis is thought to be the archetype of a universal metabolic pathway. It occurs, with variations, in nearly all organisms, both aerobic and anaerobic. The wide occurrence of glycolysis indicates that it is one of the most ancient known metabolic pathways.