Question

Whenever the cell's ATP supply is depleted, which of the following enzyme’s activity is increased?

• A. Hexokinase
• B. Pyruvate kinase
• C. Glucokinase
• D. Phosphofructokinase-1

Hint:

PFK-1 is a key regulatory enzyme in glycolysis, and its activity is enhanced during low ATP conditions to promote energy production.

Answer 1

The Correct Option is D

Step 1: Understanding ATP depletion in cells.
When ATP levels are low, cells activate pathways to restore ATP, often by increasing the rate of glycolysis. Phosphofructokinase-1 (PFK-1) is a key regulatory enzyme in glycolysis, and its activity is typically increased when ATP levels are low.
Step 2: Analyzing the options.
(1) Hexokinase: Hexokinase is involved in the initial steps of glycolysis but is not as closely regulated by ATP levels.
(2) Pyruvate kinase: Pyruvate kinase is important in the final step of glycolysis but is not the most direct regulator when ATP levels are low.
(3) Glucokinase: Glucokinase is a type of hexokinase found in the liver, and while it is involved in glucose metabolism, it is not the most important enzyme for regulating ATP levels.
(4) Phosphofructokinase-1: Correct — PFK-1 is the rate-limiting enzyme in glycolysis, and its activity is upregulated when ATP levels are depleted to increase the production of ATP.
Step 3: Conclusion.
The correct answer is (4) Phosphofructokinase-1, as its activity increases when the cell's ATP supply is low.