Final answer:
The correct inhibitors of pyruvate kinase are ATP and alanine, indicating that the cell has high energy levels and a sufficient supply of alanine.
Step-by-step explanation:
The last step in glycolysis is catalyzed by pyruvate kinase. This enzyme is tightly regulated to ensure that energy production meets the cell's demand. The enzyme's activity is decreased when ATP and alanine are abundant, which signifies high-energy conditions and sufficient supply of alanine, respectively. On the other hand, fructose-1,6-bisphosphate, an intermediate of glycolysis, increases the activity of pyruvate kinase. However, ATP acts as a negative allosteric effector, inhibiting the enzyme to prevent overproduction of energy when it is not needed.
Incomplete glycolysis under aerobic conditions will lead pyruvate to be oxidized in the mitochondria. However, during vigorous exercise, muscles ferment pyruvate into lactate causing muscle fatigue. Alanine is also produced from pyruvate during amino acid synthesis.
Therefore, the correct answer to what inhibits pyruvate kinase is: a. ATP and Alanine.