Cyclic photophosphorylation occurs under which condition?

Options

A. Anaerobic
B. Aerobic
C. Both (1) and (2)
D. None of these

Answer

**Step-by-Step Solution:**

1. **Understanding Cyclic Photophosphorylation**:
- Cyclic photophosphorylation is a process that occurs in the light-dependent reactions of photosynthesis. It involves the movement of electrons in a cyclic manner, where electrons are excited by light and then return to the original chlorophyll molecule (P700).

2. **Identifying the Electron Pathway**:
- In cyclic photophosphorylation, the excited electrons from P700 are transferred to ferredoxin, then to cytochrome, and finally to plastoquinone. Importantly, these electrons return to P700, meaning they are not lost in the process.

3. **Conditions for Cyclic Photophosphorylation**:
- Since the electrons are recycled back to P700, there is no need for water to be split (hydrolysis) to replace lost electrons. Therefore, oxygen is not released during this process.

4. **Aerobic vs. Anaerobic Conditions**:
- In non-cyclic photophosphorylation, which involves both Photosystem I (PSI) and Photosystem II (PSII), water is split, and oxygen is released. This process occurs under aerobic conditions.
- In contrast, cyclic photophosphorylation can occur under anaerobic conditions, where oxygen is not produced, as there is no water splitting.

5. **Conclusion**:
- Therefore, cyclic photophosphorylation occurs primarily under anaerobic conditions, but it can also occur in aerobic conditions when the focus is on ATP production without the release of oxygen.

**Final Answer**: Cyclic photophosphorylation occurs under anaerobic conditions.

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