Which of the following is not essentially required for chemiosmosis ?

Options

A. Membrane
B. Proton pump
C. Photolysis of `H_(2)O`
D. ATP synthase

Answer

### Step-by-Step Solution:

1. **Understanding Chemiosmosis**: Chemiosmosis refers to the movement of ions across a semipermeable membrane, which is crucial for the synthesis of ATP. This process is primarily associated with the electron transport chain in cellular respiration and photosynthesis.

2. **Identifying Components of Chemiosmosis**:
- **Membrane**: A semipermeable membrane is essential for chemiosmosis as it allows the establishment of a proton gradient.
- **Proton Pump**: This is necessary to create and maintain the proton gradient by transporting protons (H+) across the membrane.
- **ATP Synthesis**: This is the process that occurs as a result of the proton gradient, where ATP is synthesized from ADP and inorganic phosphate.

3. **Evaluating the Options**:
- **Membrane**: Required for creating the proton gradient.
- **Proton Pump**: Essential for establishing the gradient.
- **Photolysis of Water**: This process is involved in the light-dependent reactions of photosynthesis, where water is split to provide electrons. However, it is not directly required for the process of chemiosmosis itself.
- **ATP Synthesis**: Directly involved in the chemiosmosis process as it utilizes the proton gradient to synthesize ATP.

4. **Conclusion**: Among the options provided, photolysis of water is not essentially required for chemiosmosis, as it does not directly contribute to the movement of protons across the membrane or the synthesis of ATP.

### Final Answer:
**Photolysis of Water** is not essentially required for chemiosmosis.

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