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 the cytochrome where terminal oxidation takes place in the electron transport chain, we can break down the solution into the following steps:

### Step-by-Step Solution:

1. **Understanding the Electron Transport Chain (ETC)**:
- The electron transport chain is a series of protein complexes and other molecules that transfer electrons from electron donors to electron acceptors via redox reactions. This process is crucial for ATP production in cellular respiration.

2. **Identifying the Components**:
- The ETC consists of four main protein complexes (Complex I, II, III, and IV) and several mobile electron carriers. Each complex plays a role in the transfer of electrons.

3. **Focusing on Terminal Oxidation**:
- Terminal oxidation refers to the final step in the electron transport chain where electrons are transferred to the final electron acceptor. In aerobic respiration, this acceptor is molecular oxygen (O2).

4. **Locating the Cytochrome**:
- The terminal oxidation occurs at the fourth protein complex, which is known as Complex IV. This complex contains cytochromes, specifically cytochrome a and cytochrome a3.

5. **Finalizing the Answer**:
- Among these cytochromes, cytochrome a3 is specifically responsible for the terminal oxidation, where it facilitates the transfer of electrons to oxygen, resulting in the formation of water.

### Conclusion:
- The cytochrome where the terminal oxidation takes place in the electron transport chain is **cytochrome a3**.