Which enzyme catalyzes the link reaction ?

Options

A. Pyruvate carboxylase
B. Malate dehydrogenase
C. Pyruvate dehydrogenase
D. Acetyl CoA dehydrogenase

Answer

To determine which enzyme catalyzes the link reaction, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Link Reaction**:
- The link reaction occurs between glycolysis and the Krebs cycle. In glycolysis, glucose is converted into two molecules of pyruvate.

2. **Conversion of Pyruvate**:
- The pyruvate produced in glycolysis is then converted into acetyl coenzyme A (acetyl CoA). This conversion is crucial as acetyl CoA enters the Krebs cycle.

3. **Identifying the Enzyme**:
- The enzyme responsible for catalyzing the conversion of pyruvate to acetyl CoA is essential to identify.

4. **Analyzing the Options**:
- A) Pyruvate Carboxylase: This enzyme converts pyruvate to oxaloacetate, not acetyl CoA.
- B) Malate Dehydrogenase: This enzyme is involved in the Krebs cycle, not in the conversion of pyruvate.
- C) Pyruvate Dehydrogenase: This enzyme catalyzes the conversion of pyruvate to acetyl CoA.
- D) Acetyl Coenzyme A Dehydrogenase: This enzyme does not catalyze the link reaction.

5. **Conclusion**:
- The enzyme that catalyzes the link reaction (the conversion of pyruvate to acetyl CoA) is **C) Pyruvate Dehydrogenase**.

### Final Answer:
C) Pyruvate Dehydrogenase

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