Question

although the path of one glucose molecule through glycolysis generates a total of four atp molecules, there is a net gain of only two atp for each glucose molecule that enters the pathway. why does the passage of one glucose molecule through glycolysis have a payoff of only two atp molecules? two atp molecules are generated by each of the pyruvic acid molecules generated by glycolysis. two atp molecules are used to convert pyruvic acid to a form that can enter the citric acid cycle. two atp molecules are used to synthesize two nadh molecules in the second phase of glycolysis. two atp molecules are used in the initial phase of glycolysis, reducing the net gain to two atp.

Explanation:

Glycolysis has an energy - investment phase where 2 ATP are used to prime the glucose molecule for breakdown. After the energy - payoff phase where 4 ATP are produced, the net gain is 4 - 2 = 2 ATP due to the initial ATP investment.

Answer:

D. Two ATP molecules are used in the initial phase of glycolysis, reducing the net gain to two ATP.