canonical glycolysis

Definition

Target type: biologicalprocess

The glycolytic process that begins with the conversion of glucose to glucose-6-phosphate by glucokinase activity. Glycolytic processes are the chemical reactions and pathways resulting in the breakdown of a carbohydrate into pyruvate, with the concomitant production of a small amount of ATP. [GOC:dph, ISBN:0201090910, ISBN:0879010479]

Canonical glycolysis is a fundamental metabolic pathway that occurs in the cytoplasm of nearly all living organisms. It is the process by which glucose, a six-carbon sugar, is broken down into pyruvate, a three-carbon molecule, in a series of ten enzymatic steps. This process generates energy in the form of ATP (adenosine triphosphate), a molecule that serves as the primary energy currency of cells. The pathway can be divided into two phases: the preparatory phase and the payoff phase.

The preparatory phase involves the initial steps of glucose breakdown, where glucose is phosphorylated to form glucose-6-phosphate, then isomerized to fructose-6-phosphate, and finally phosphorylated again to form fructose-1,6-bisphosphate. These phosphorylation reactions consume two molecules of ATP. The molecule is then cleaved into two three-carbon molecules, glyceraldehyde-3-phosphate (G3P) and dihydroxyacetone phosphate (DHAP). DHAP is then isomerized to G3P, ensuring that both molecules can proceed through the next phase.

The payoff phase begins with the oxidation and phosphorylation of G3P to 1,3-bisphosphoglycerate. This reaction generates a high-energy phosphate bond that is then transferred to ADP, forming ATP. This process is repeated for the second G3P molecule, resulting in a net gain of two ATP molecules. Subsequent steps involve the conversion of 1,3-bisphosphoglycerate to 3-phosphoglycerate, followed by isomerization to 2-phosphoglycerate, dehydration to phosphoenolpyruvate (PEP), and finally the transfer of a phosphate group from PEP to ADP, producing pyruvate and another ATP molecule.

In summary, canonical glycolysis yields a net gain of two ATP molecules, two NADH molecules (nicotinamide adenine dinucleotide, a reducing agent used in subsequent energy production), and two pyruvate molecules per glucose molecule. These pyruvate molecules can then enter the citric acid cycle (also known as the Krebs cycle) for further energy production or be used in other metabolic pathways, such as gluconeogenesis (glucose synthesis) or fermentation. Glycolysis is essential for life as it provides a continuous supply of ATP, the main energy source for cellular processes. It is also a crucial pathway for the synthesis of various essential molecules, including amino acids, lipids, and nucleotides.'
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Proteins (17)

Compounds (282)