In photosystem-I, the first electron acceptor is

Options

A. ferredoxin
B. cytochrome
C. plastocyanin
D. an iron sulphur protein

Answer

To solve the question "In photosystem-I, the first electron acceptor is," we need to analyze the components involved in photosystem I and identify the correct answer among the given options.

### Step-by-Step Solution:

1. **Understanding Photosystem I (PS I)**:
- Photosystem I is also known as P700 because it absorbs light at a wavelength of 700 nm.
- It is located on the outer surface of the thylakoid membrane.

2. **Identifying Electron Acceptors**:
- In the context of photosystems, electron acceptors are molecules that receive electrons during the light-dependent reactions of photosynthesis.
- The question specifically asks for the first electron acceptor in Photosystem I.

3. **Evaluating the Options**:
- **Option 1: Paradoxine (FD)** - This is involved in electron transport but is not the first electron acceptor. Therefore, this option is incorrect.
- **Option 2: Cytochrome** - Cytochromes are known to be electron carriers and can act as electron acceptors. This option is likely correct.
- **Option 3: Plastocyanin (PC)** - This is a copper-containing protein involved in electron transport but not the first electron acceptor in PS I. Thus, this option is incorrect.
- **Option 4: Iron Sulfur Protein** - Similar to plastocyanin, this protein is involved in electron transport but is not the first electron acceptor. Therefore, this option is also incorrect.

4. **Conclusion**:
- The first electron acceptor in Photosystem I is **Cytochrome** (Option 2).

### Final Answer:
The first electron acceptor in Photosystem I is **Cytochrome**.

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