Question

Phosphofructokinase is an allosteric enzyme that catalyzes the conversion of fructose-6-phosphate to fructose-1,6-bisphosphate, an early step of glycolysis. An increased accumulation of ATP (an allosteric regulator of PFK) would be expected to...
a inhibit the enzyme and slow the rates of glycolysis and the citric acid cycle.
b activate the enzyme and slow the rates of glycolysis and the citric acid cycle.
c. inhibit the enzyme and thus increase the rates of glycolysis and the citric acid cycle.
d. activate the enzyme and increase the rates of glycolysis and the citric acid cycle.
e. ATP would have no effect on the rates of glycolysis and the citric acid cycle.

Answer 1

Answer:

The correct answer is a Inhibit the enzyme and slow the rates of Glycolysis and citric acid cycle.

Explanation:

ATP accumulation result in blocking the activity of the rate limiting enzyme  of glycolysis  Phosphofructokinase that catalyses the conversion of fructose-6-phosphate to fructose -1,6-bisphosphate .

            ATP is an Allosteric inhibitor of Phosphofructokinase enzyme and this enzymatic inhibition decreases the rate of glycolysis and as the rate of glycolysis decreases the rate of TCA cycle is also decreased because TCA cycle  depends on glycolytic end product Pyruvate. As glycolysis rate is decreased pyruvate is not formed in a sufficient amount to carry out its conversion to Acetyl CoA  and enters into TCA Cycle.