Cyanide causes irreversible inhibition of cytochrome oxidase. It

Options

A. Combines with an amino acid
B. Destroys tertiary structure
C. Attaches to iron
D. All the above.

Answer

**Step-by-Step Solution:**

1. **Understanding Cyanide's Action**: Cyanide is a potent inhibitor of cytochrome oxidase, an essential enzyme in the electron transport chain. This enzyme plays a critical role in cellular respiration by facilitating the transfer of electrons to oxygen.

2. **Mechanism of Inhibition**: The inhibition caused by cyanide is irreversible. This means that once cyanide binds to the enzyme, it cannot be removed, and the enzyme's activity is permanently lost.

3. **Binding Site**: Cyanide specifically binds to the iron (Fe) component of cytochrome oxidase. This iron is crucial for the enzyme's function, as it is involved in the transfer of electrons.

4. **Consequences of Inhibition**: When cyanide binds to the iron in cytochrome oxidase, it prevents the transport of electrons from the enzyme to oxygen. This halts the process of oxidative phosphorylation, leading to a lack of ATP production and ultimately cell death.

5. **Conclusion**: The correct answer to the question is that cyanide causes irreversible inhibition of cytochrome oxidase by attaching to the iron within the enzyme.

**Final Answer**: Cyanide causes irreversible inhibition of cytochrome oxidase by attaching to iron within the enzyme, preventing the transport of electrons to oxygen.

---