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
Physiological uncoupler is- 
Select and explain. 
A. Thermogonin, B. 2, 4 nitrophenol, C. 2, 4Dinitrophenol, D. Oligomycin
A: Thermogonin
Answer: A: Thermogonin 
Explanation: Ans. is 'a' i.e., Thermogenin o Amongst the given options, a, b and c are uncouplers.o However, only thermogenin, among these three is a natural (physiological) uncoupler.i) Natural:- Thermogenin, thyroxineii) Synthetic:- 2,4-dinitrophenol (2,4-DNP), 2,4-dinitrocresol (2,4-DNC), and CCCP (chlorocarbonylcyanidephenyl hydrazone).