Which of the following enzymes involved in Kreb's cycle is not present in the mitochondrial matrix?

Options

A. Aconistase
B. Malate dehydrogenase
C. Fumarase
D. Succinate dehydrogenas

Answer

**Step-by-Step Solution:**

1. **Understanding the Krebs Cycle**: The Krebs cycle, also known as the citric acid cycle or TCA cycle, is a series of chemical reactions used by all aerobic organisms to generate energy. It takes place in the mitochondria of cells.

2. **Identifying Enzymes in the Krebs Cycle**: The Krebs cycle involves several enzymes, including aconitase, malate dehydrogenase, fumarase, and succinate dehydrogenase. Each of these enzymes catalyzes specific reactions within the cycle.

3. **Location of Enzymes**: Most enzymes involved in the Krebs cycle are located in the mitochondrial matrix, which is the innermost compartment of the mitochondria. However, some enzymes may be located in different parts of the mitochondria.

4. **Analyzing the Options**:
- Aconitase: Present in the mitochondrial matrix.
- Malate dehydrogenase: Present in the mitochondrial matrix.
- Fumarase: Present in the mitochondrial matrix.
- Succinate dehydrogenase: This enzyme is unique because it is located in the inner mitochondrial membrane (specifically in the cristae) and is involved in both the Krebs cycle and the electron transport chain (ETC).

5. **Conclusion**: Among the options provided, succinate dehydrogenase is the enzyme that is not present in the mitochondrial matrix but rather in the inner mitochondrial membrane (cristae). Therefore, the correct answer is succinate dehydrogenase.

**Final Answer**: Succinate dehydrogenase is the enzyme involved in the Krebs cycle that is not present in the mitochondrial matrix.

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