26. Match the entries in Column-1 with those in Column-2
Column-1                                     Column-2
P. Vitamin B1                               1. Thiamine pyrophosphate
Q. Carboxypeptidase                  2. Aconitase
R. TCA cycle                                 3. Sucrose
S. Reducing sugar                       4. Zn2+
5. Riboflavin
6. Lactose
(A) P-1; Q-4; R-2; S-6
(B) P-5; Q-1; R-2; S-3
(C) P-1; Q-4; R-5; S-6
(D) P-5; Q-2; R-1; S-6

Vitamin B1 matches with thiamine pyrophosphate as its coenzyme form, while carboxypeptidase requires Zn²⁺. The TCA cycle involves aconitase with a Fe-S cluster, and reducing sugars include lactose. The correct option is (A) P-1; Q-4; R-2; S-6.​

Correct Matching

• P. Vitamin B1 → 1. Thiamine pyrophosphate: Vitamin B1, or thiamine, functions primarily as thiamine pyrophosphate (TPP), a coenzyme in decarboxylation reactions like those in pyruvate dehydrogenase.​

• Q. Carboxypeptidase → 4. Zn²⁺: This exopeptidase uses zinc ions at its active site to coordinate water for peptide bond hydrolysis.​

• R. TCA cycle → 2. Aconitase: Aconitase catalyzes citrate to isocitrate conversion in the tricarboxylic acid (TCA) cycle, relying on a [4Fe-4S] cluster.​

• S. Reducing sugar → 6. Lactose: Lactose, a β-1,4 glucose-galactose disaccharide, has a free anomeric carbon on glucose, enabling reduction of Fehling’s or Benedict’s reagents.​

This combination corresponds to option (A).​

Why Other Options Fail

Option (B) P-5; Q-1; R-2; S-3 incorrectly pairs Vitamin B1 with riboflavin (Vitamin B2, FMN/FAD coenzymes) and sucrose (non-reducing) as a reducing sugar.​

Option (C) P-1; Q-4; R-5; S-6 wrongly links TCA cycle to riboflavin, which supports flavoproteins like succinate dehydrogenase but not aconitase directly.​

Option (D) P-5; Q-2; R-1; S-6 mismatches Vitamin B1 to riboflavin, carboxypeptidase to aconitase (an Fe-S enzyme), and TCA cycle to TPP (used in alpha-ketoglutarate dehydrogenase, not primarily defining TCA).​

Quick Fact Table

These pairings test core biochemistry knowledge on vitamins, enzymes, and carbohydrates for competitive exams.​