During vigrous exercise, when oxygen is inadequate for cellular respiration , reduction of pyruvic acid is catalysed by

Options

A. Lactate dehydrogenase
B. Pyruvic acid decarboxylase
C. Alcohol dehydrogenase
D. Pyruvate thiokinase

Answer

To solve the question regarding the reduction of pyruvic acid during vigorous exercise when oxygen is inadequate for cellular respiration, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Cellular Respiration**:
- Cellular respiration is the process by which cells convert glucose into energy. It can occur in two ways: aerobic respiration (with oxygen) and anaerobic respiration (without oxygen).

2. **Glycolysis Process**:
- The process begins with glucose, which undergoes glycolysis. Glycolysis is the breakdown of glucose into two molecules of pyruvic acid (or pyruvate).

3. **Fate of Pyruvic Acid**:
- The fate of pyruvic acid depends on the availability of oxygen.
- If oxygen is present, pyruvic acid enters the aerobic respiration pathway (Krebs cycle).
- If oxygen is absent or in low supply (as during vigorous exercise), pyruvic acid undergoes anaerobic respiration.

4. **Anaerobic Pathway**:
- In the absence of oxygen, pyruvic acid is converted into lactate (lactic acid) through a process called fermentation.

5. **Enzyme Involved**:
- The conversion of pyruvic acid to lactate is catalyzed by the enzyme lactate dehydrogenase.

6. **Conclusion**:
- Therefore, during vigorous exercise when oxygen is inadequate, the reduction of pyruvic acid is catalyzed by lactate dehydrogenase.

### Final Answer:
The correct answer is **lactate dehydrogenase**.

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