Anoxygenic photosynthesis does not involve

Options

A. photosystems
B. ATP synthesis
C. `COunderset(2)` fixation
D. photolysis of water

Answer

### Step-by-Step Solution:

1. **Understanding Anoxygenic Photosynthesis**:
- Anoxygenic photosynthesis is a type of photosynthesis that does not produce oxygen as a byproduct. It occurs in certain bacteria and is characterized by the absence of water as an electron donor.

2. **Conditions for Anoxygenic Photosynthesis**:
- This process occurs under anaerobic conditions, meaning it takes place in environments where oxygen is not present.

3. **Electron Donors in Anoxygenic Photosynthesis**:
- Instead of water (H₂O), which is used in oxygenic photosynthesis, anoxygenic photosynthesis utilizes substances like hydrogen sulfide (H₂S) as an electron donor.

4. **Photolysis of Water**:
- In oxygenic photosynthesis, water undergoes photolysis, resulting in the release of oxygen. However, in anoxygenic photosynthesis, this process does not occur, and therefore, oxygen is not released.

5. **Photosystems Involvement**:
- Anoxygenic photosynthesis does involve photosystems, which are necessary for the light reactions of photosynthesis. This is a common misconception that needs clarification.

6. **ATP and CO₂ Fixation**:
- ATP is generated during the light reactions of anoxygenic photosynthesis, and carbon dioxide (CO₂) fixation occurs to produce sugars, which are essential for the bacteria.

7. **Conclusion**:
- The correct answer to the question "Anoxygenic photosynthesis does not involve" is **photolysis of water**. This is because, unlike oxygenic photosynthesis, the process does not split water to release oxygen.

### Final Answer:
Anoxygenic photosynthesis does not involve **photolysis of water**.

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