Ferredoxin is a constituent of

Options

A. PS-I
B. PS-II
C. Hill reaction
D. `P_(680)`

Explanation

**Step-by-Step Solution:**

1. **Identify Ferredoxin**: Ferredoxin is an iron-containing protein that plays a crucial role in various biological processes, particularly in photosynthesis.

2. **Location of Ferredoxin**: It is soluble in nature, which indicates that it can be found in the chloroplasts of plant cells. Chloroplasts are the organelles where photosynthesis occurs.

3. **Role in Photosynthesis**: Ferredoxin is a key component of Photosystem I (PS I), which is one of the two photosystems involved in the light-dependent reactions of photosynthesis.

4. **Function of Ferredoxin**: The primary function of ferredoxin is to facilitate electron transport. It transfers electrons to the reductase complex during the light reactions of photosynthesis.

5. **Conversion Process**: When ferredoxin transfers electrons to the reductase complex, it leads to the conversion of NAD+ (Nicotinamide adenine dinucleotide) to NADPH (Nicotinamide adenine dinucleotide phosphate). NADPH is an essential reducing agent used in the Calvin cycle to synthesize glucose.

6. **Conclusion**: Based on the above points, ferredoxin is a constituent of Photosystem I (PS I).

**Final Answer**: Ferredoxin is a constituent of Photosystem I (PS I).

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