This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Biochemistry
Cytochrome oxidase can be poisoned by all, EXCEPT: 
Select and explain. 
A. Cyanide, B. Hydrogen sulphide, C. Carbon monoxide, D. Carbon dioxide
D: Carbon dioxide
Answer: D: Carbon dioxide 
Explanation: Cytochrome oxidase is a haemo-protein widely distributed in many tissues. It is the terminal component of the chain of respiratory carriers found in mitochondria and transfers electrons resulting from the oxidation of substrate molecules by dehydrogenases to their final acceptor, oxygen. The enzyme is poisoned by carbon monoxide, cyanide, and hydrogen sulfide. Ref: Harper 28thedition, chapter 12.