In the electron transport chain , the cytochrome where the terminal oxidation takes place is

Options

A. Cyt b
B. Cyt `a_3`
C. Cyt a
D. Cyt c

Answer

To solve the question regarding which cytochrome in the electron transport chain (ETC) is responsible for terminal oxidation, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Electron Transport Chain (ETC)**:
- The ETC is a series of protein complexes located in the inner mitochondrial membrane. It facilitates the transfer of electrons from electron donors to electron acceptors through redox reactions.

2. **Identifying the Components of the ETC**:
- The main components of the ETC include various cytochromes and other electron carriers. Some of the key cytochromes are:
- Cytochrome b
- Cytochrome c
- Cytochrome a
- Cytochrome a3

3. **Function of Cytochromes in the ETC**:
- Each cytochrome plays a specific role in the transfer of electrons. Electrons are passed from one cytochrome to another, ultimately leading to the reduction of oxygen.

4. **Identifying the Terminal Cytochrome**:
- The terminal oxidation in the ETC occurs when electrons are transferred to molecular oxygen (O2). The specific cytochrome that facilitates this final step is cytochrome a3.
- Cytochrome a3 is part of the cytochrome oxidase complex, which is the last complex in the electron transport chain.

5. **Conclusion**:
- Based on the understanding of the electron transport chain and the roles of different cytochromes, the cytochrome where the terminal oxidation takes place is **Cytochrome a3**.

### Final Answer:
The correct option is **Cytochrome a3**.

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