Exemplar Problems

Question:

Explain the concept of substrate-level phosphorylation in glycolysis.

Answer:

• Substrate-level phosphorylation is a process in which ATP is generated directly during a metabolic reaction.

• In glycolysis, substrate-level phosphorylation occurs twice.

• During the conversion of glyceraldehyde-3-phosphate to 1,3-bisphosphoglycerate, one molecule of ATP is produced.

• Later, during the conversion of phosphoenolpyruvate to pyruvate, a second molecule of ATP is produced.

• These ATP molecules are generated by transferring a phosphate group from an intermediate substrate directly to ADP, forming ATP.

• Substrate-level phosphorylation is distinct from oxidative phosphorylation, where ATP is generated indirectly through the electron transport chain and ATP synthase.