Question

List the major steps, primary reactants and products, and regulatory process of either glycolysis or Kreb's cycle.

Answer 1

Glycolysis is the sequence of reactions converting glucose to pyruvate or lactate,with the production of ATP.

Glycolysis takes place in all cells of the body. The enzymes for glycolysis pathway are present in the cytosomal fraction of the cell.

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The primary reactants of glycolysis pathway are one molecule of glucose and 2 molecules of ATP.

The major steps in glycolysis pathway are :

A. Energy investment phase or priming stage

1 Glucose is phosphorylated to glucose 6-phosphate by consuming one ATP.

2. Glucose 6-phosphate undergoes isomerization and forms fructose 6-phosphate.

3. Fructose 6-phosphate is phosphorylated to fructose 1,6-bisphosphate by consuming one ATP.

B. Splitting phase

4. Fructose 1,6 - bisphosphate is split into dihydroxyacetone phosphate and glyceraldehyde 3-phosphate.

C. Energy generation phase.

5. Glyceraldehyde 3-phosphate is converted to 1,3- bisphosphoglycerate with the formation of NADH+ H+. NADH pass through electron transport chain and produce 6ATP by oxidative phosphorylation.

6. 1,3-bisphoaphoglycerate is converted to 3-phosphoglycerate with the production of one ATP (SUBSTRATE LEVEL PHOSPHORYLATION), gets converted to 2- phosphoglycerate and to phosphoenol pyruvate.

7. Phosphoenol pyruvate is converted to pyruvate with the production of one ATP.

Number of ATP synthesized :

Glyceraldehyde 3-phosphate dehydrogenase : 6

(2NADH, ETC , Oxidative phosphorylation)

Phosphoglycerate kinase : 2

(Substrate level phosphorylation)

Pyruvate kinase (substrate level phosphorylation). : 2

Two ATP are consumed in step 1&3 : (-2)

Net ATP synthesis in glycolysis in aerobic condition - 8.

Regulation of glycolysis :

Three enzymes hexokinase, phosphofructokinase and pyruvate kinase regulate glycolysis. They catalyse the irreversible reactions.