MCAT Biology Question #2: Answer and Rationale

2. The information in the passage suggests that glycolysis:

A) is important for maintaining normal Na+ and K+ levels in skeletal muscle.

B) facilitates membrane permeability in skeletal muscle.

C) impedes the function of the Na+ and K+ ATPase in skeletal muscle.

D) is regulated by the Na+ and K+ ATPase in skeletal muscle.

Answer Analysis

The correct answer is A.

Rationale: For this question, you must apply your understanding of glycolysis to the data shown in Figure 1. The data reveals that an increase in concentration of IAA results in a higher Na+ to K+ concentration ratio when compared to the control sample. This increase must be correlated with the role of IAA in disruption of glycolysis. This finding is further supported by reduced lactate production at higher concentrations of IAA, which is shown in Figure 1. This is because IAA prevents the formation of NADH, which is used in pyruvate reduction to lactate. The combination of the proposed role of IAA and the results from Figure 1 should lead you to the conclusion that glycolysis is important to the Na+K+ ATPase and, therefore, important to the maintenance of the concentration ratio of Na+ to K+ in skeletal muscle.

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