Non-cyclic photophosphorylation differs from cyclic photophosphorylation

Options

A. As it requires light energy
B. In synthesis of ATP
C. As it requires only PS-I
D. As it involves photolysis of water

Answer

To answer the question regarding how non-cyclic photophosphorylation differs from cyclic photophosphorylation, we can break down the differences step by step.

### Step-by-Step Solution:

1. **Definition of Photophosphorylation**:
- Photophosphorylation is the process by which ATP is formed utilizing the energy of light. It occurs during photosynthesis in plants.

2. **Types of Photophosphorylation**:
- There are two types: cyclic and non-cyclic photophosphorylation.

3. **Cyclic Photophosphorylation**:
- In cyclic photophosphorylation, only **ATP** is produced.
- It involves only **Photosystem I (PS1)**.
- No oxygen is released during this process.
- It does not involve the **photolysis of water** (the splitting of water molecules).
- There is no need for an external electron donor.

4. **Non-Cyclic Photophosphorylation**:
- In non-cyclic photophosphorylation, both **ATP** and **NADPH** are produced.
- It requires both **Photosystem I (PS1)** and **Photosystem II (PS2)**.
- Oxygen is released as a byproduct of this process.
- It involves the **photolysis of water**, which provides electrons.
- An external electron donor is required, typically from water or H2S.

5. **Comparison**:
- **ATP Production**: Cyclic produces only ATP, while non-cyclic produces ATP and NADPH.
- **Photosystems Involved**: Cyclic requires only PS1; non-cyclic requires both PS1 and PS2.
- **Oxygen Release**: Cyclic does not release oxygen; non-cyclic does release oxygen.
- **Photolysis of Water**: Cyclic does not involve photolysis; non-cyclic involves photolysis of water.
- **External Electron Donor**: Cyclic does not require an external donor; non-cyclic requires one.

6. **Conclusion**:
- The key difference between non-cyclic and cyclic photophosphorylation is that non-cyclic photophosphorylation involves the photolysis of water and produces both ATP and NADPH, while cyclic photophosphorylation only produces ATP and does not involve water splitting.

### Final Answer:
The correct statement that differentiates non-cyclic photophosphorylation from cyclic photophosphorylation is that **non-cyclic photophosphorylation involves the photolysis of water**.