This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: FMGE 2019, Subject name: Biochemistry
Type IV complex of ETC is inhibited by 
Select and explain. 
A. Oligomycin, B. Antimycin, C. Cyanide, D. CO2
C: Cyanide
Answer: C: Cyanide 
Explanation: Cyanide is probably the most potent inhibitor of ETC (Complex IV). It binds to Fe3+ of cytochrome oxidase blocking mitochondrial respiration leading to cell death. Cyanide poisoning causes death due to tissue asphyxia (mostly of the central nervous system) In Acute cyanide poisoning Amyl nitrite is given followed by sodium thiosulphate. This is an example of Chemical antagonism i.e. one drug binding to other making it unavailable in body.