1. Commitment of Sugar for glycolysis- Phosphorylated products are negatively charged and impermeable to the cell membrane through passive diffusion. Glycolysis operates in cytosol and as a result first step of phosphorylation inhibits the passive movement of the particular glucose moiety and drive it to participate in further steps of glycolysis.

2. Activation of sugar- In the 1st and 3rd step of glycolysis, two phosphorylation reactions add potential energy into the molecule and hence activate the sugar to participate into the cleavage reaction to form two 3 carbon sugar moiety. 

STEP 5: Interconversion of the triose phosphates-Three carbon sugar formed in step 4 undergoes internal conversion  and as glyceraldehyde-3 phosphate can readily be able to enter into the next step, the ketose generated in step 4 is reversibly convereted into the glyceraldehydes-3 phosphate by triose-3-phosphate isomerase.

Figure 36.4: Different Reactions of Glycolysis.

 

STEP 6: Glyceraldehyde-3-phosphate to 1,3 bis-phospho-glycerate-In this step, one molecule of NADH is produced after oxidation of aldehyde group of glyceraldehyde-3-phosphate with  the help of enzyme glyceraldehyde-3-phosphate dehydrogenase.

STEP 7: In this step, phosphate group from 1,3 bis-phosphoglycerate is removed by phosphoglycerate kinase with an acyl phosphate group transfer to ADP to generate ATP molecule.

STEP 8: Conversion of 3-phosphoglycerate to 2-phosphoglycerate- In a two step mechanism, phosphoglycerate mutase catalyzes a reversible shift of phosphoryl group to form 2-phosphoglycerate.