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What are the 10 reactions of glycolysis?

Published in Biochemistry 2 mins read

Glycolysis, a fundamental metabolic pathway, involves a sequence of ten enzyme-catalyzed reactions that break down glucose into pyruvate, generating ATP and NADH. Here are the ten reactions of glycolysis:

  1. Phosphorylation of Glucose: Glucose is phosphorylated by hexokinase (or glucokinase in the liver and pancreas) to form glucose-6-phosphate (G6P). This step consumes one ATP molecule.

  2. Isomerization of Glucose-6-phosphate: Glucose-6-phosphate is isomerized to fructose-6-phosphate (F6P) by phosphoglucose isomerase (PGI).

  3. Phosphorylation of Fructose-6-phosphate: Fructose-6-phosphate is phosphorylated by phosphofructokinase-1 (PFK-1) to form fructose-1,6-bisphosphate (F1,6BP). This is a rate-limiting step and consumes another ATP molecule.

  4. Cleavage of Fructose 1,6-bisphosphate: Fructose-1,6-bisphosphate is cleaved by aldolase into two 3-carbon molecules: dihydroxyacetone phosphate (DHAP) and glyceraldehyde-3-phosphate (G3P).

  5. Isomerization of Dihydroxyacetone Phosphate: Dihydroxyacetone phosphate is isomerized to glyceraldehyde-3-phosphate by triose phosphate isomerase (TPI). Only G3P can proceed directly to the next step of glycolysis.

  6. Oxidation of Glyceraldehyde-3-phosphate: Glyceraldehyde-3-phosphate is oxidized and phosphorylated by glyceraldehyde-3-phosphate dehydrogenase (GAPDH) to form 1,3-bisphosphoglycerate (1,3-BPG). This reaction reduces NAD+ to NADH.

  7. Phosphoryl Transfer from 1,3-bisphosphoglycerate: 1,3-bisphosphoglycerate transfers a phosphate group to ADP, forming ATP and 3-phosphoglycerate (3PG). This reaction is catalyzed by phosphoglycerate kinase (PGK) and represents the first ATP-generating step (substrate-level phosphorylation).

  8. Isomerization of 3-phosphoglycerate: 3-phosphoglycerate is isomerized to 2-phosphoglycerate (2PG) by phosphoglycerate mutase (PGM).

  9. Dehydration of 2-phosphoglycerate: 2-phosphoglycerate is dehydrated by enolase to form phosphoenolpyruvate (PEP).

  10. Phosphoryl Transfer from Phosphoenolpyruvate: Phosphoenolpyruvate transfers a phosphate group to ADP, forming ATP and pyruvate. This reaction is catalyzed by pyruvate kinase (PK) and represents the second ATP-generating step (substrate-level phosphorylation).

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