Q.41 Correctly match the Coenzyme with its respective involvement in a specific
Reaction type.
Coenzyme                                                Reaction type
P. Thiamine pyrophosphate                1. Acyl group transfer
Q. Tetrahydrofolate                              2. Transfer of one carbon group
R. Flavin adenine dinucleotide          3. Transfer of methyl group
S. 5′-Deoxyadenosyl cobalamin        4. Oxidation-reduction
5. Aldehyde transfer
(A) P-5; Q-2; R-4; S-3
(B) P-5; Q-1; R-2; S-3
(C) P-1; Q-2; R-4; S-5
(D) P-5; Q-3; R-1; S-2

Thiamine pyrophosphate facilitates aldehyde transfer in decarboxylation reactions, while tetrahydrofolate handles one-carbon group transfers. The correct matching identifies these specific biochemical roles accurately.​

Correct Answer

Option (A) P-5; Q-2; R-4; S-3 provides the precise pairing: Thiamine pyrophosphate (P) with aldehyde transfer (5), Tetrahydrofolate (Q) with one-carbon group transfer (2), Flavin adenine dinucleotide (R) with oxidation-reduction (4), and 5′-Deoxyadenosyl cobalamin (S) with methyl group transfer (3).​

Coenzyme Functions

Thiamine pyrophosphate (TPP), derived from vitamin B1, acts as a coenzyme in reactions involving aldehyde transfer, such as the decarboxylation of pyruvate to acetaldehyde by pyruvate decarboxylase, where it forms a transient “active aldehyde” intermediate. Tetrahydrofolate (THF) serves as a carrier for one-carbon groups at various oxidation states, essential in purine and thymidylate synthesis. Flavin adenine dinucleotide (FAD) participates in oxidation-reduction reactions, shuttling electrons in processes like the electron transport chain and fatty acid oxidation. 5′-Deoxyadenosyl cobalamin, a form of vitamin B12, enables methyl group transfer in reactions such as methionine synthesis from homocysteine.​

Option Analysis

• (A) Correct: Matches TPP to aldehyde transfer (decarboxylases), THF to one-carbon transfer (folate cycle), FAD to redox (dehydrogenases), and cobalamin to methyl transfer (methylmalonyl-CoA mutase/methylation).​

• (B) Incorrect: Misassigns THF to acyl group transfer (1), which aligns with coenzyme A, not folate.​

• (C) Incorrect: Wrongly pairs TPP with acyl transfer (1) instead of aldehyde handling and cobalamin with aldehyde (5), overlooking B12’s adenosyl role in rearrangements/methylation.​

• (D) Incorrect: Confuses THF with methyl transfer (3), specific to S-adenosylmethionine or cobalamin, while THF broadly transfers formyl/methylene groups.​