Electron donor to the enzyme nitrogenase in nitrogen metabolism and to NADP+ in non cyclic electron transport in light reaction is

Options

A. Plastoquinone
B. Ferredoxin
C. Phenophytin
D. Quinone

Answer

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks for the electron donor that serves two specific functions:
- It donates electrons to the enzyme nitrogenase in nitrogen metabolism.
- It also donates electrons to NADP+ during the non-cyclic electron transport in the light reaction of photosynthesis.

2. **Identifying the Enzyme and Processes**:
- **Nitrogenase**: This enzyme is crucial for nitrogen fixation, a process where atmospheric nitrogen (N2) is converted into ammonia (NH3), which plants can use.
- **Non-Cyclic Electron Transport**: This process occurs during the light reactions of photosynthesis, where light energy is converted into chemical energy. NADP+ is reduced to NADPH, which is used in the Calvin cycle.

3. **Evaluating Possible Electron Donors**: The options provided are:
- Plastoquinone
- Ferredoxin
- Phenophytin
- Quinone

4. **Analyzing Each Option**:
- **Plastoquinone**: Involved in the electron transport chain but not directly as an electron donor to nitrogenase.
- **Ferredoxin**: Known to act as an electron carrier and is involved in both nitrogen fixation (donating electrons to nitrogenase) and in the light reactions (donating electrons to NADP+).
- **Phenophytin**: Primarily involved in the light reactions but does not donate electrons to nitrogenase.
- **Quinone**: Similar to plastoquinone, it plays a role in electron transport but not specifically as an electron donor to nitrogenase.

5. **Conclusion**: Based on the analysis, the correct electron donor that serves both functions (to nitrogenase and NADP+) is **ferredoxin**.

**Final Answer**: Ferredoxin

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