All enzymes of TCA cycle are located in the mitochondrial matrix except one which is located in inner mitochondrial membranes in eukaryotes and in cytosol in prokaryotes. This enzyme is

Options

A. malate dehydrogenase
B. succinate dehydrogenase
C. lactate dehydrogenase
D. isocitrate dehydrogenase

Answer

**Step-by-Step Solution:**

1. **Understanding the TCA Cycle**: The TCA cycle, also known as the Krebs cycle or citric acid cycle, is a series of enzymatic reactions that occur in the mitochondria. Most of the enzymes involved in this cycle are located in the mitochondrial matrix.

2. **Identifying the Exception**: The question specifies that all enzymes of the TCA cycle are located in the mitochondrial matrix except one. This means we need to identify which enzyme is not located in the matrix.

3. **Location of Enzymes**: In eukaryotes, the TCA cycle enzymes are primarily found in the mitochondrial matrix. However, one enzyme is located in the inner mitochondrial membrane. In prokaryotes, this enzyme is found in the cytosol.

4. **Listing the Options**: The options provided are:
- a) Malate dehydrogenase
- b) Succinate dehydrogenase
- c) Lactate dehydrogenase
- d) Isocitrate dehydrogenase

5. **Analyzing Each Option**:
- **Malate dehydrogenase**: This enzyme is located in the mitochondrial matrix.
- **Succinate dehydrogenase**: This enzyme is unique as it is located in the inner mitochondrial membrane in eukaryotes and in the cytosol in prokaryotes.
- **Lactate dehydrogenase**: This enzyme is also located in the mitochondrial matrix.
- **Isocitrate dehydrogenase**: This enzyme is found in the mitochondrial matrix as well.

6. **Conclusion**: Based on the analysis, the only enzyme that fits the criteria of being located in the inner mitochondrial membrane in eukaryotes and in the cytosol in prokaryotes is **succinate dehydrogenase**. Therefore, the correct answer is **option b) succinate dehydrogenase**.

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