This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Respiratory chain, Subject name: Biochemistry
Cytochrome C oxidase is inhibited by 
Select and explain. 
A. Barbiturate, B. 2, 4-dinitrophanol, C. H2S, D. Rotenon
C: H2S
Answer: C: H2S 
Explanation: Site-III (Complex IV) * Cyanide Inhibits terminal * H2S * Azide transfer of electrons to molecular O2 * Co (Carbon monoxide): Inhibits Cyt. oxidase by combining with O2 binding site. It can be reversed by illumination with light.Ref: MN Chatterjea Textbook of Medical Biochemistry, 8th edition, page no: 143