The enzyme phosphofructokinase (PFK) catalyses a key step in glycolysis. PFK is inhibited by high levels of which of the following molecules?
A) glucose and NAD⁺
B) AMP and ATP
C) ATP and citrate
D) citrate and CO₂

Question

Quizplus · Accepted Answer

ATP and citrate are both high energy molecules that signal to the cell that there is already enough energy available, and that more glucose should not be broken down for further energy production. Therefore, they inhibit the enzyme PFK in order to regulate glycolysis. Glucose and NAD+ are not inhibitors of PFK, and AMP and ATP are both involved in regulating glycolysis, but in opposite ways (AMP promotes glycolysis while ATP inhibits it), so they cannot both be inhibitors of PFK. Similarly, citrate and CO₂ are both products of the TCA cycle and do not play a direct role in regulating glycolysis.

The Enzyme Phosphofructokinase (PFK) Catalyses a Key Step in Glycolysis