Question

Which of the following is a coenzyme?
a. Nicotinamide
b. Riboflavin
c. Pantothenic Acid
d. All of the above

Answer 1

Hint: Coenzymes are little organic molecules that are essential for certain enzymes for them to function. Coenzymes are non-protein parts. Many are obtained from vitamins chiefly those that are phosphorylated derivatives of water-soluble vitamins. Coenzymes take part in catalysis when they unite to the active site of the enzyme (called apoenzyme) and finally form the active enzyme (called holoenzyme).

Complete answer:
Coenzymes are a non-protein piece of an enzyme. These are organic molecules that attach to the protein molecule to structure the active enzyme. Nicotinamide, riboflavin, and pantothenic acid are coenzymes that bind with the apoenzyme and step up the reaction.

Nicotinamide gets integrated into NAD+ works as an electron acceptor in metabolic reactions. It acts as a coenzyme for the natural reaction like glycolysis. During glycolysis, it accepts the electron and hydrogen, alters to NADH, and makes ATP.
Riboflavin is a hydrophilic vitamin B2​. It is a vital part of coenzyme flavin adenine dinucleotide (FAD) and flavin mononucleotide (FMN).

Pantothenic acid is a water-soluble vitamin B5​. It is requisite to the enzyme pyruvate dehydrogenase to manufacture coenzyme-A (CoA) which is a chief substrate for Krebs cycle. Pantothenic acid is a predecessor for the fusion of coenzyme A (CoA, CoASH) and forms part of the “wavering sulfhydryl arm” of the fatty acid synthase complex.

Hence, the correct answer is option (D).

Note: Dissimilar to coenzymes, true cofactors are reusable non-protein molecules that do not contain carbon (inorganic). Typically, cofactors are metal ions such as iron, zinc, cobalt, and copper that slackly bind to an enzyme’s active site. They must also be added to the diet as many organisms do not naturally produce metal ions.