Which one of the following category of electron carriers is not common in ETS of both photosynthesis and respiration ?

Options

A. Quinone
B. plastocyanin
C. Fe-S
D. Cytochrome

Answer

To solve the question regarding which category of electron carriers is not common in the electron transport system (ETS) of both photosynthesis and respiration, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the ETS**: The electron transport system (ETS) is a series of protein complexes that transport electrons. It plays a crucial role in both photosynthesis and respiration.

2. **Identify the Locations**:
- In photosynthesis, the ETS occurs in the chloroplasts, specifically within the thylakoid membrane.
- In respiration, the ETS occurs in the mitochondria.

3. **List Common Electron Carriers**:
- Common electron carriers in both processes include:
- **Quinone**: A type of electron carrier that participates in both processes.
- **Iron-sulfur proteins**: These proteins are involved in the transfer of electrons in both photosynthesis and respiration.
- **Cytochrome**: Another common electron carrier found in both systems.

4. **Identify Unique Electron Carriers**:
- **Plastocyanin**: This is an electron carrier that is specific to photosynthesis. It acts as an electron acceptor in the photosystem II and transfers electrons to photosystem I. It does not participate in the respiration process.

5. **Conclusion**: Since plastocyanin is not involved in respiration, it is the correct answer to the question. Therefore, the category of electron carriers that is not common in the ETS of both photosynthesis and respiration is **Plastocyanin**.

### Final Answer:
The electron carrier that is not common in the ETS of both photosynthesis and respiration is **Plastocyanin**.

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