Photosystem I (PS I) and photosystem II (PSII) ae named -

Options

A. in the sequence of their discovery
B. in the sequence in which they function during light reaction
C. in the sequence of their positions
D. in the sequence of e transfer

Answer

To answer the question regarding the naming of Photosystem I (PS I) and Photosystem II (PS II), we can break down the solution into the following steps:

### Step-by-Step Solution:

1. **Understanding Photosystems**: Photosystems are complexes involved in the light-dependent reactions of photosynthesis. There are two main types: Photosystem I (PS I) and Photosystem II (PS II).

2. **Identifying the Options**: The question provides four options regarding the naming of PS I and PS II:
- Option A: In the sequence of their discovery.
- Option B: In the sequence in which they function during light reaction.
- Option C: In the sequence of their position.
- Option D: In the sequence of electron transfer.

3. **Analyzing the Options**:
- **Option A** suggests that the naming is based on the order in which they were discovered.
- **Option B** implies that the naming is based on their functional sequence during the light reaction.
- **Option C** indicates that their position in the thylakoid membrane determines their name.
- **Option D** suggests that the naming is based on the sequence of electron transfer.

4. **Determining the Correct Option**:
- PS I was discovered before PS II, which is why they are named as such. This means that the correct basis for their naming is indeed the sequence of their discovery, not their functional order or any other criteria.

5. **Conclusion**: Therefore, the correct answer to the question is **Option A: in the sequence of their discovery**.