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
Malonate is a competitive inhibitor of 
Select and explain. 
A. Complex I, B. Complex II, C. Complex III, D. Complex IV
B: Complex II
Answer: B: Complex II 
Explanation: Barbiturates such as amobarbital inhibit electron transpo Complex I by blocking the transfer from Fe-S to Q. At sufficient dosage, they are fatal in vivo. Antimycin A and dimercaprol inhibit the respiratory chain at Complex III. The classic poisons H2S, carbon monoxide, and cyanide inhibit Complex IV and can therefore totally arrest respiration. Malonate is a competitive inhibitor of Complex II Reference: Harper; 30th edition; Page no: 132