Cytochromes are

Options

A. `O_2` acceptor
B. `H_2` acceptor
C. Electron acceptor
D. All of these

Answer

**Step-by-Step Solution:**

1. **Understanding Cytochromes**: Cytochromes are proteins that play a crucial role in the electron transport chain, which is part of cellular respiration. They contain heme groups that can undergo oxidation and reduction, allowing them to accept and donate electrons.

2. **Role in Electron Transport Chain**: In the electron transport chain, cytochromes are involved in transferring electrons from one molecule to another. They are arranged in a specific order based on their electron affinity, meaning they have varying abilities to accept electrons.

3. **Electron Transfer Process**: The process begins with NADH donating electrons to coenzyme Q. From coenzyme Q, electrons are passed to cytochrome B, then to cytochrome C1, followed by cytochrome C, and finally to cytochrome A and cytochrome A3.

4. **Final Electron Acceptor**: The last cytochrome, cytochrome A3, donates the electrons to molecular oxygen (O2). This oxygen acts as the final electron acceptor in the electron transport chain, which is essential for the production of ATP through oxidative phosphorylation.

5. **Conclusion**: Since cytochromes facilitate the transfer of electrons and ultimately help in the reduction of oxygen, they can be classified as electron acceptors.

**Final Answer**: Cytochromes are electron acceptors.

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