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 understand the differences between non-cyclic photophosphorylation and cyclic photophosphorylation, we can break down the key features of each process step by step.

### Step-by-Step Solution:

1. **Definition of Photophosphorylation**:
- Photophosphorylation is the process by which ATP is formed utilizing light energy. There are two types: non-cyclic and cyclic photophosphorylation.

2. **Energy Requirement**:
- Both non-cyclic and cyclic photophosphorylation require light energy to initiate the process. This is a common feature of both processes.

3. **ATP Synthesis**:
- Both processes result in the synthesis of ATP. However, the mechanism and the amount of ATP produced can differ.

4. **Photosystems Involvement**:
- Non-cyclic photophosphorylation involves both Photosystem I (PSI) and Photosystem II (PSII). In contrast, cyclic photophosphorylation primarily involves only Photosystem I.

5. **Electron Flow**:
- In non-cyclic photophosphorylation, electrons are transferred from water molecules (through photolysis) to NADP+, forming NADPH. In cyclic photophosphorylation, the electrons are recycled back to PSI, which means they do not reduce NADP+.

6. **Photolysis of Water**:
- A significant difference is that non-cyclic photophosphorylation involves the photolysis (splitting) of water molecules to release oxygen, protons, and electrons. This does not occur in cyclic photophosphorylation.

7. **Oxygen Production**:
- Non-cyclic photophosphorylation produces oxygen as a byproduct due to the photolysis of water. In contrast, cyclic photophosphorylation does not produce oxygen.

### Conclusion:
The main differences can be summarized as follows:
- Non-cyclic photophosphorylation involves both Photosystem I and II, while cyclic photophosphorylation involves only Photosystem I.
- Non-cyclic photophosphorylation includes the photolysis of water, producing oxygen, while cyclic photophosphorylation does not.

### Final Answer:
Non-cyclic photophosphorylation differs from cyclic photophosphorylation primarily in that it involves the photolysis of water and the production of oxygen, while cyclic photophosphorylation does not.

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