A complex enzyme system of mitochondira functional outside Krebs cycle is

Options

A. Pyruvate kinase
B. Pyruvate dehydrogenase
C. Enolase
D. `alpha`-Ketoglutrate dehydrogenase

Answer

To solve the question regarding the complex enzyme system of mitochondria that functions outside the Krebs cycle, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Context**:
- The question asks for a complex enzyme system in mitochondria that operates outside the Krebs cycle.

2. **Identifying the Options**:
- The options provided are:
- A) Pyruvate kinase
- B) Pyruvate dehydrogenase
- C) Enolase
- D) Alpha-ketoglutarate dehydrogenase

3. **Analyzing Each Option**:
- **Pyruvate Kinase**: This enzyme is involved in glycolysis, specifically in the last steps, and is located in the cytoplasm, not in mitochondria.
- **Pyruvate Dehydrogenase**: This enzyme complex is located in the mitochondria and catalyzes the conversion of pyruvate into acetyl-CoA, which is a crucial step before entering the Krebs cycle.
- **Enolase**: Like pyruvate kinase, enolase is also part of glycolysis and functions in the cytoplasm.
- **Alpha-Ketoglutarate Dehydrogenase**: This enzyme is part of the Krebs cycle, specifically involved in the conversion of alpha-ketoglutarate to succinyl-CoA.

4. **Conclusion**:
- The only enzyme from the options that is a complex enzyme system in mitochondria and functions outside the Krebs cycle is **Pyruvate Dehydrogenase**. This enzyme plays a critical role in linking glycolysis and the Krebs cycle by converting pyruvate into acetyl-CoA.

### Final Answer:
**B) Pyruvate dehydrogenase**

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