<prompt> Which of the following vitamin is a component of ETC:Vitamin B12RiboflavinNicotinic acidThiamine  <response>: In ETC, Complex I FMN, Fe-S Complex II FAD , Fe-S are involved, which contains FAD, FMN made of riboflavin. Therefore Riboflavin Vitamin B2 is a component of ETC. Vitamin Constituent of Riboflavin Vitamin B2 FAD, FMN. Nicotinic acid Niacin Vitamin B3 NAD, NADP. Pantothenic acid Vitamin B5 Coenzyme A. There are two different questions asked on this, BE CAREFUL: Vitamin, which is component of ETC, is Riboflavin as it is present in complex I II, in the form of FMN FAD respectively Figure below. NAD or NADH is not a component of ETC complexes. NADH is a just a substrate for ETC complex I Figure below So, one can interpret that Vitamins which are used in ETC are both B2 B3 as FADH2 or NADH can be the staing materials for ETC 