This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Proteins and Amino Acids, Subject name: Biochemistry
Each of the following is a physiological uncoupler EXCEPT: 
Select and explain. 
A. 2,4 dinitrophenol, B. Thyroid hormone, C. Unconjugated bilirubin, D. Long chain fatty acid
A: 2,4 dinitrophenol
Answer: A: 2,4 dinitrophenol 
Explanation: Ans. A. 2,4 dinitrophenol* Compounds that can uncouple or delink the ETC from oxidative phosphorylation, such compounds are known as uncouplers* As a result ATP synthesis doesn't occur.* 2,4 Dinitrophenol is an example of chemical uncoupler.Chemical uncouplers* Chemical uncouplers* Physiological uncouplers# 2, 4 dinitrophenol (has been extensively studied)# Thyroid hormones# Dinitrocresol# Long chain fatty acids# Pentachlorophenol# Unconjugated bilirubin# Tri fluoro carbonyl cyanide phenyl hydra zone (FCCP)* These act as uncouplers only at high concentration# Aspirin (high doses)