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
[{'content': 'Cyanide is toxic because it \nSelect and explain. \nA. Inhibits cytochrome oxidase, B. Forms cyan meth Hb, C. Inhibits ATP carrier in mitochondria, D. Inhibits Na-K-ATP ase', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Site-III (Complex IV) (CYTOCHROME OXIDASE ) * Cyanide Blocks electron transfer from cyt b to c1 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', 'role': 'assistant'}]