In photoautotrophic bacteria, the reaction centre is

Options

A. `P_700`
B. `B_690`
C. `B_890`
D. `B_1700`

Answer

To answer the question regarding the reaction center in photoautotrophic bacteria, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Photoautotrophic Bacteria**:
- Photoautotrophic bacteria are organisms that can perform photosynthesis using light energy to convert carbon dioxide and water into glucose and oxygen. They utilize specific pigments to capture light energy.

2. **Identifying the Reaction Center**:
- In higher plants, the reaction centers are known as P680 and P700, which correspond to Photosystem II (PSII) and Photosystem I (PSI), respectively. However, these systems are not present in photoautotrophic bacteria.

3. **Exploring the Options**:
- The options provided include P700, P680, B890, and B1700.
- P700 and P680 are associated with higher plants and not applicable to bacteria.
- B1700 is also incorrect as it does not represent the reaction center in these bacteria.

4. **Correct Identification of the Reaction Center**:
- The correct reaction center in photoautotrophic bacteria is B890. The "B" indicates that it is specific to bacteria, and 890 refers to the wavelength of light that is maximally absorbed by this reaction center.

5. **Conclusion**:
- Therefore, the reaction center in photoautotrophic bacteria is B890.

### Final Answer:
The reaction center in photoautotrophic bacteria is **B890**.

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