A photosystem contains

Options

A. pigments, electron acceptor & a reaction centre
B. photons, protons pigments & hydrogen acceptor
C. `PO_(4), ADP & H_""^(+)`
D. (1) & (2) both

Answer

**Step-by-Step Solution:**

1. **Understanding Photosystems**: Photosystems are essential components of the light reactions of photosynthesis, which occur in the presence of light. They are primarily involved in capturing light energy and converting it into chemical energy.

2. **Types of Photosystems**: There are two main types of photosystems in plants: Photosystem I (PSI) and Photosystem II (PSII).
- Photosystem I (PSI) absorbs light at a wavelength of 700 nm and is also known as P700.
- Photosystem II (PSII) absorbs light at a wavelength of 680 nm and is also known as P680.

3. **Components of a Photosystem**: A photosystem consists of three main components:
- **Reaction Center**: This is primarily made up of chlorophyll a, which absorbs light energy and emits electrons.
- **Pigments**: In addition to chlorophyll a, there are other pigments such as different types of chlorophyll molecules and carotenoids that assist in capturing light energy.
- **Electron Acceptors**: These are molecules that accept the electrons emitted by chlorophyll a after it absorbs light. Examples include quinones and iron-sulfur complexes.

4. **Analyzing the Options**:
- **Option 1**: "Pigments, electron acceptor, and a reaction center" - This accurately describes the components of a photosystem.
- **Option 2**: "Photons, proton, pigments, and hydrogen acceptor" - This does not correctly describe the components of a photosystem.
- **Option 3**: "Phosphate, ADP, and H plus ion" - This is unrelated to the structure of photosystems.
- **Option 4**: "Both one and two" - Since option two is incorrect, this option is also incorrect.

5. **Conclusion**: The correct answer is **Option 1**, which states that a photosystem contains pigments, electron acceptors, and a reaction center.

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