What does phosphofructokinase do?

What does phosphofructokinase do?

• A. It removes a phosphate group from ATP.
• B. It adds a phosphate group to fructose 6-phosphate.
• C. It converts fructose 6-phosphate to fructose 1,6-bisphosphate.
• D. It oxidizes glucose to gluconate.

Answer: (C)

Phosphofructokinase drives a key phosphorylation step in glycolysis. It uses ATP to attach a phosphate to fructose-6-phosphate, producing fructose-1,6-bisphosphate and ADP. This exact transformation is why it’s the best answer: it names both the substrate (fructose-6-phosphate) and the precise product (fructose-1,6-bisphosphate), marking a major control point that commits glucose to glycolysis. This step is highly regulated by the cell’s energy status, so it acts as a checkpoint to speed up or slow down glycolysis as needed.

Other options miss the specificity or mechanism: it doesn’t simply remove a phosphate from ATP, and while it does add a phosphate to fructose-6-phosphate, the crucial detail is forming fructose-1,6-bisphosphate, not just one phosphate addition. Oxidizing glucose to gluconate is not part of glycolysis.