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
Uncoupler in ETC - 
Select and explain. 
A. H2S, B. Antimycin a, C. 2,4-dinitrophenol, D. Barbiturates
C: 2,4-dinitrophenol
Answer: C: 2,4-dinitrophenol 
Explanation: Ans. C. 2, 4-dinitrophenolUncouplers of oxidative phosphorylation in mitochondria inhibit the coupling between the electron transport and phosphorylation reactions and thus inhibit ATP synthesis without affecting the respiratory chain and ATP synthase (H(+)- ATPase). Physiological uncouplers- long chain fatty acids, thyroxin, calcium ions, brown adipose tissue Pathological uncouplers-2,4 dinitrophenol, 2,4 dinitroocresol, CCCP, FCCP, valinomycin, high dose aspirinClass with examplesAffected complex* or reactionInhibitors of electron transport Rotenone, Piericidin AAmytal, SeconalThenoyltrifluoroacetoneAntimycin A.DimercaprolHCN, H2 SHN3 , COI FMN-Q and or cytb(Fe3+)I FMN-Q and or cytb(Fe3+)II Peptide-FAD-Q and/or cytbIII cytb(Fe2+)-cytcl(Fe3+)(perhaps at NHI)IV cytc(Fe2+)-O2 IV cytc(Fe2+)-O2 Inhibitors of oxidative phosphorylation OiigomycinRutamycinAtractylateBongkrekateInhibit respiration (NADH-O2 or Succinate O2 ) when coupled to phosphorylationUncouplers of oxidative phosphorylation2,4 dinitrophenolDicoumarolValinomycin *Gramicidin A *Stimulate respiration when rate is limited by phosphorylation or blocked by oiigomycin.