Glycolysis Introduction, Pathway , Diagram & Summary
The Embden-Meyerhof pathway or Glycolysis.. Microorganisms employ several metabolic pathways to catabolize glucose and other sugars.
During the energy-requiring phase of glycolysis. Two ATP are spent to form an unstable sugar with two phosphate groups, which then splits to form 2 three-carbon molecules that are isomers of each other.
which shows in the diagram below.
A phosphate group is transferred from ATP to glucose, making glucose-6-phosphate. Glucose-6-phosphate is more reactive than glucose.
Glucose-6-phosphate is converted into its isomer, fructose-6-phosphate.
A phosphate group is transferred from ATP to fructose-6-phosphate, producing fructose-1,6-bisphosphate. This step is catalyzed by the enzyme phosphofructokinase.
Fructose-1,6-bisphosphate splits to form two three-carbon sugars: dihydroxyacetone phosphate and glyceraldehyde-3-phosphate. They are isomers of each other, but only one—glyceraldehyde-3-phosphate—can directly continue through the next steps of glycolysis.
DHAP is converted into glyceraldehyde-3-phosphate. The two molecules exist in equilibrium, but the equilibrium is “pulled” strongly downward, in the scheme of the diagram above, as glyceraldehyde-3-phosphate is used up.
In the second half of glycolysis, the three-carbon sugars formed in the first half of the process go through a series of additional transformations, ultimately turning into pyruvate.
Glyceraldehyde-3-phosphate is converted into 1,3-bisphosphoglycerate. This is a redox reaction in which NAD+ is converted to NADH. by enzyme glyceraldehyde-3-phosphate dehydrogenase.
1,3-bisphosphoglycerate is converted to 3-phosphoglycerate by phosphoglycerate kinase. This step converts an ADP to an ATP.
3-phosphoglycerate is converted to 2-phosphoglycerate by phosphoglycerate mutase
phosphoglycerate is converted to phosphoenolpyruvate (PEP) by enolase.This reaction releases a water molecule.
Phosphoenolpyruvate (PEP) is converted to pyruvate by pyruvate kinase. An ADP is converted to an ATP in this reaction.
All of these reactions will happen twice for one molecule of glucose.
Overall, glycolysis converts one six-carbon molecule of glucose into two three-carbon molecules of pyruvate. The net products of this process are two molecules of ATP produced and two molecules of NADH.