The initial metabolic pathway of cellular respiration in which a series of reactions happening in the cytosol results in the conversion of a monosaccharide, often glucose, into pyruvate, and the concomitant production of a relatively small amount of high-energy biomolecule, such as ATP
Cellular respiration is a series of metabolic processes wherein the biochemical energy is harvested from organic substance (e.g. glucose) and stored in energy-carriers (e.g. ATP) for use in energy-requiring activities of the cell. The major steps or processes of cellular respiration are (1) glycolysis, (2) Krebs cycle, and (3) oxidative phosphorylation.
Glycolysis is the stage in cellular respiration that is involved in the cellular degradation of the simple sugar, glucose to pyruvate in order to yield high-energy molecules such as ATP and NADH.
The most common and well-known type of glycolysis is the Embden-Meyerhof-Parnas pathway, which was first describe by Gustav Embden , Otto Meyerhof, and Jakub Karol Parnas. Other alternative pathways are exemplified by the Entner-Doudoroff pathway and the pentose phosphate pathway.
In Embden-Meyerhof-Parnas pathway, glycolysis is comprised of two phases: (1) the energy-investment phase (where ATP is consumed) and (2) the energy-payoff phase (where ATP is produced). The splitting of sugar during the energy-investment phase characterizes glycolysis in this regard since glucose is split into two triose phosphate molecules: glyceraldehyde phosphate and dihydroxyacetone phosphate. The glyceraldehyde phosphate proceeds to the energy-payoff phase whereas its isomer, dihydroxyacetone phosphate, has to be converted to glyceraldehyde phosphate (via isomerase) before it can proceed.
Word origin: Greek glykys (“sweet”, referring to sugar) + Iyein (“to loosen”)