An enzyme absent in mitochondrial ETS is

Options

A. FeS protease
B. Glucose 6-phosphate dehydrogenase
C. NADH dehydrogenase
D. Cytochrome c-oxidase.

Answer

To solve the question regarding which enzyme is absent in the mitochondrial electron transport system (ETS), we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Question**: The question asks for an enzyme that is not present in the mitochondrial electron transport system (ETS).

2. **Identify the Options**: The options provided are:
- FeAs (iron-sulphide protease)
- Glucose 6-phosphate dehydrogenase
- NADH dehydrogenase
- Cytochrome C oxidase

3. **Recall the Function of the ETS**: The electron transport system is the final stage of cellular respiration, where electrons are transferred through a series of proteins and coenzymes, leading to ATP production. Key components include cytochromes and various dehydrogenases.

4. **Analyze Each Option**:
- **FeAs (iron-sulphide protease)**: This enzyme is involved in various metabolic processes but is not specifically known for its role in the ETS.
- **Glucose 6-phosphate dehydrogenase**: This enzyme is primarily involved in the pentose phosphate pathway and is not part of the ETS.
- **NADH dehydrogenase**: This enzyme is a key component of the ETS, facilitating the transfer of electrons from NADH.
- **Cytochrome C oxidase**: This is also a crucial enzyme in the ETS, involved in the final step of electron transfer.

5. **Determine the Correct Answer**: Among the options, glucose 6-phosphate dehydrogenase is the only enzyme that is not part of the mitochondrial electron transport system.

### Conclusion:
The enzyme that is absent in the mitochondrial electron transport system is **glucose 6-phosphate dehydrogenase**.

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