Question

Substrate -level phosphorylation accounts for approximately what percentage of the ATP formed by the reactions of glycolysis?

• A. $0\%$
• B. $2\%$
• C. $10\%$
• D. $100\%$

Answer 1

The correct option is D $100\%$

Substrate-level phosphorylation is the direct transfer of phosphate group to ADP to form ATP. It accounts of 100% of the ATP formed by the reactions of glycolysis. The first substrate-level phosphorylation occurs when 1, 3 - diphosphoglyceraldehyde is converted to 1, 3 - diphosphoglyceric acid and 2 NADH${}_2$ are formed, that is 6 ATP are formed. The 1, 3-diphosphoglyceric acid is then dephosphorylated to 3 phosphoglyceric acid producing 2 ATP via substrate-level phosphorylation. The second substrate-level phosphorylation occurs when phosphoenolpyruvic acid is converted to pyruvic acid producing 2 ATP molecules.

Thus, the correct answer is option D.