Question

Coenzymes FMN and FAD are derived from
A. Vitamin $C$
B. Vitamin $B_6$
C. Vitamin $B_1$
D. Vitamin $B_2$

Answer 1

Hint: Enzymes are composed of one or several polypeptide chains but many enzymes exhibit the catalytic activity only in association with certain non-protein substances. Such substances are called cofactors. In these enzymes the protein portion is known as apoenzyme.

Complete answer:
Coenzymes : They are also organic compounds but their association with the apoenzyme last for a short period of time, usually occurring during the course of catalysis. The essential chemical components of many coenzymes are vitamins, e.g., coenzyme nicotinamide adenine dinucleotide (NAD) and NADP contain the vitamin niacin.

Now let us know more about vitamins given in options :-
> Option A - Vitamin $C$: it is also known as ascorbic acid and is essential for formation of RBCs and production of antibodies. It is good for bones , teeth and gums and acts as an antioxidant. Thus this option is not correct.

> Option B - Vitamin $B_6$: it is also known as pyridoxine. It is mainly used in protein metabolism and not in FMN and FAD production. Its deficiency causes dermatitis and anaemia.

> Option C - Vitamin $B_1$: it is also known as Thiamine . It is required for the repair and growth of tissues. It acts as thiamine pyrophosphate in Krebs cycle.

> Option D - Vitamin $B_2$: it is also known as riboflavin . It acts as FMN and FAD. FMN acts in the electron transport chain and FAD acts in the Krebs cycle. Thus this option is correct.

Hence, the correct answer is option (D).

Additional information:
Hydrolysis of the phosphate bonds of ATP releases their bond energy for driving energy-dependent reactions and processes. Nicotinamide and riboflavin nucleotides act as coenzymes of oxidising enzymes.

Note: FMN is known as Flavin mononucleotide and FAD is known as Flavin adenine dinucleotide. Purine and pyrimidine nucleotides polymerise to form nucleic acids. Higher purine and pyrimidine nucleotides, particularly adenosine triphosphate, store energy in their high-energy phosphate bonds. They are formed during photosynthesis and respiration.