In which of the following aspect PS-I and PS-II differ to each other ?

Options

A. Reaction centre
B. Location on thylakoid membrane
C. Redox behaviour
D. All the above

Answer

To answer the question regarding the differences between Photosystem I (PS-I) and Photosystem II (PS-II), we will analyze the aspects mentioned in the options: reaction center, location on the thylakoid membrane, and redox behavior.

### Step-by-Step Solution:

1. **Identify the Reaction Center**:
- Photosystem I (PS-I) has a reaction center known as P700, which absorbs light at a wavelength of 700 nm.
- Photosystem II (PS-II) has a reaction center known as P680, which absorbs light at a wavelength of 680 nm.
- **Conclusion**: The reaction centers of PS-I and PS-II differ in their absorption wavelengths.

2. **Location on the Thylakoid Membrane**:
- PS-I is located on the outer surface of the thylakoid membrane.
- PS-II is located on the inner surface of the thylakoid membrane.
- **Conclusion**: The location of PS-I and PS-II on the thylakoid membrane is different.

3. **Redox Behavior**:
- PS-I is involved in both cyclic and non-cyclic photophosphorylation and does not produce molecular oxygen.
- PS-II is primarily involved in non-cyclic photophosphorylation and is responsible for the photolysis of water, which produces molecular oxygen.
- **Conclusion**: The redox behavior of PS-I and PS-II is different, with PS-II being involved in oxygen evolution.

4. **Final Conclusion**:
- Since PS-I and PS-II differ in their reaction centers, locations on the thylakoid membrane, and redox behavior, the correct answer to the question is "all of the above."

### Final Answer:
The correct option is **all of the above**.

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