The carbohydrates "Ribose" present in DNA, is A. A pentose sugar B. present in pyranose from C. in "D" configuration D. a reducing sugar, when free E. in α-anomeric form
Choose the correct answer from the options given below :
(A)A, C and D Only✓ Correct
(B)A, B and E Only
(C)B, D and E Only
(D)A, D and E Only
Answer: (A)
Solution
The pentose sugar actually present in DNA is 2-deoxy-D-ribose, in which the 2'-hydroxyl of ribose is replaced by hydrogen, and it occurs in the β-furanose form when linked into the nucleotide.
A. It is a five-carbon sugar — a pentose — true.
B. In DNA it occurs in the five-membered furanose ring, not the six-membered pyranose ring — false.
C. Its configuration at the reference carbon is D — true.
D. When free — not locked into a glycosidic bond through its anomeric carbon — it retains a reactive anomeric centre and reduces Fehling's/Tollens' reagent — true.
E. The sugar is joined to the base and the sugar–phosphate backbone in the β-anomeric configuration in DNA, not the α form — false.
Statements A, C and D are correct.
JEE Main · 2025 · 24 Jan 2025 · Shift 1 · Single correct option
