Glycolysis is a ten-step process that breaks down glucose into two pyruvate molecules.
Glycolysis has seven reversible processes and three irreversible phases.
1st, 3rd and last steps of glycolysis are irreversible.
In the first step, glucose is converted to glucose 6-phosphate, in the third step, fructose 6-phosphate is converted to fructose 1, 6-bisphosphate, and in the last step, PEP (phosphoenolpyruvate) is converted to pyruvic acid.
These irreversible steps in glycolysis are catalyzed by hexokinase, phosphofructokinase, and pyruvate kinase respectively.
The 2nd 4th 5th 6th 7th 8th 9th steps of glycolysis are reversible in nature.
Glucose-6-phosphate is transformed into its isomer, fructose-6-phosphate, in the second step. Fructose-1,6-bisphosphate divides into two three-carbon sugars, dihydroxyacetone phosphate (DHAP) and glyceraldehyde-3-phosphate, in the fourth step and in the fifth step DHAP is converted into glyceraldehyde-3-phosphate.
In step 6, Two half reactions occur simultaneously: 1) Glyceraldehyde-3-phosphate (one of the three-carbon sugars formed in the initial phase) is oxidized, and 2) Reduction of NAD+ to NADH. Both these steps result in the formation of 1,3-bisphosphoglycerate.
In step 7, 1,3-bisphosphoglycerate transfers one of its phosphate groups to ADP, resulting in the formation of an ATP molecule and 3-phosphoglycerate.
In step 8, 2-phosphoglycerate, the isomer of 3-phosphoglycerate, is produced.
Step 9 results in the loss of a water molecule, converting 2-phosphoglycerate into phosphoenolpyruvate.
