In the first reaction of glycolysis, glucose is converted to glucose 6‑phosphate. a. The phosphate comes from ATP. b. A kinase is an enzyme that transfers the terminal phosphate of to a substrate. c. The product of this reaction is then phosphorylated to fructose‑6‑phosphate. d. Fructose‑6‑phosphate is then phosphorylated by a second reaction, giving.

Glycolysis involves a series of phosphorylation, dephosphorylation and oxidation reactions.

Explanation:

Glycolysis, as the name implies is the splitting of glucose. It occurs in the cytoplasm of the cell. When a glucose molecule is split by glycolysis, the following are produced:

2 ATP (Adenosine Triphosphate) molecules;

2 NADH (Nicotinamide Adenine Dinucleotide Hydrogen);

2 pyruvate molecules and;

2 water molecules.

The glycolytic pathway is a ten-step reaction, the first five reactions are the preparatory reaction (2 ATP molecules are used up in these reactions) while the remaining five are the pay-off reaction (4 ATP molecules are generated).

Reaction 1: Glucose is phosphorylated (addition of phosphate group) by the enzyme hexokinase to produce glucose 6-phosphate.

Reaction 2: Glucose 6-phosphate undergoes an isomerization reaction by the action of the enzyme phosphoglucomutase to produce fructose 6-phosphate.

Reaction 3: Fructose 6-phosphate is acted upon by a kinase enzyme phosphofructokinase which adds phosphate group from an ATP molecule to produce fructose 1,6-bisphosphate.

Reaction 4: The enzyme aldolase splits fructose 1,6-bisphosphate into isomers (an aldehyde and a ketone), glyceraldehyde 3-phosphate, and dihydroxyacetone phosphate respectively.

Reaction 5: The enzyme triose phosphate converts dihydroxyacetone phosphate into glyceraldehyde 3-phosphate. This implies that there are two molecules of glyceraldehyde 3-phosphate which will serve as the substrate for the pay-off reactions.

Reaction 6: The enzyme glyceraldehyde 3-phosphate dehydrogenase oxidizes glyceraldehyde 3-phosphate and adds a phosphate group to the oxidized glyceraldehyde 3-phosphate to produce 1,3-bisphosphoglycerate.

Reaction 7: The enzyme phosphoglyceromutase undergoes a dephosphorylation reaction to convert the 2 molecules of 1,3-bisphosphoglycerate to 2 molecules of 3-phosphoglycerate

Reaction 8: The 2 molecules of 3-phosphoglycerate undergoes isomerization reaction by the action of the enzyme phosphoglyceromutase to produce 2 molecules of 2-phosphoglycerate.

Reaction 9: Each of the 2-phosphoglycerate molecules undergo hydrolysis (removal of a water molecule) to produce 2 molecules of phosphoenolpyruvate.

Reaction 10: The enzyme pyruvate kinase removes a phosphate group from each of the phosphoenolpyruvate molecules and adds it to ADP (Adenosine Diphosphate) molecules to produce 2 ATP molecules and 2 pyruvate molecules.