Correctly match the Coenzyme with its respective involvement in a specific Reaction type. Coenzyme: P. Thiamine pyrophosphate; Q. Tetrahydrofolate; R. Flavin adenine dinucleotide; S. 5'-Deoxyadenosyl cobalamin. Reaction type: 1. Acyl group transfer; 2. Transfer of one carbon group; 3. Transfer of methyl group; 4. Oxidation-reduction; 5. Aldehyde transfer.
P-5; Q-2; R-4; S-3
P-5; Q-1; R-2; S-3
P-1; Q-2; R-4; S-5
P-5; Q-3; R-1; S-2
ANSWER
Option A: P-5; Q-2; R-4; S-3.
Official answer: ASource: Official answer key, GATE 2025 BT (IIT Roorkee)
Thiamine pyrophosphate (TPP) carries an activated aldehyde (hydroxyalkyl) unit, as in transketolase and pyruvate decarboxylase. So P matches 5, aldehyde transfer. It is not an acyl group carrier in the sense of coenzyme A or lipoamide.
Tetrahydrofolate (THF) carries one-carbon units (formyl, methenyl, methylene, methyl). So Q matches 2, transfer of one carbon group.
Flavin adenine dinucleotide (FAD) accepts and donates electrons and hydrogen: . So R matches 4, oxidation-reduction.
5'-Deoxyadenosyl cobalamin is a vitamin B12 coenzyme. Of the five reaction types listed, the only one that fits a cobalamin coenzyme is methyl group transfer, because the other four are taken by P, Q and R and acyl transfer belongs to none of the four coenzymes. So S matches 3. Strictly, the 5'-deoxyadenosyl form catalyses carbon-skeleton rearrangements, as in methylmalonyl-CoA mutase, which shifts a group between adjacent carbons. The methylcobalamin form is the one that transfers methyl groups. The question treats B12 as a methyl-group coenzyme, and this is the only reading consistent with a full set of matches.
Check each option against the three secure pairs P-5, Q-2 and R-4. Option B has Q-1, so THF is wrongly an acyl carrier. Option C has P-1, so TPP is wrongly an acyl carrier. Option D has Q-3 and R-1, so FAD is wrongly an acyl carrier. Option A is the only one with P-5, Q-2 and R-4, so it is the answer: P-5; Q-2; R-4; S-3.
KEY IDEA
Match each coenzyme to the group it carries: TPP carries an aldehyde unit, THF carries one-carbon units, FAD carries electrons and hydrogen in redox reactions, and cobalamin (vitamin B12) is the methyl and rearrangement coenzyme. Three firm matches (P, Q, R) leave only option A.
WATCH OUT FOR
Calling TPP an acyl carrier because it sits in the pyruvate dehydrogenase complex. In that complex TPP carries a hydroxyethyl (aldehyde-level) unit, and the acyl group is carried by lipoamide and coenzyme A. Another slip is assigning THF to methyl transfer alone, when it carries one-carbon units at several oxidation levels.
From the GATE 2025 BT paper. Every question of this paper · Download the full paper · All 6 Enzymes questions, with notes
