Identify the given structure
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → Nucleoside
The structure is a pentose sugar (ribose: OH groups at 2′ and 3′, \( \ce{CH2OH} \) at 5′) with a base attached at the 1′ position and no phosphate group. A unit of base + sugar is a nucleoside; when it is linked to phosphoric acid at the 5′-position it becomes a nucleotide.
Why the other options are incorrect
Option (1) Nucleotide — Incorrect. A nucleotide also has a phosphate group at C-5′; the 5′-carbon here carries only an OH.
Option (3) Vitamins — Incorrect. Vitamins are a different group of organic compounds; this sugar-base unit is a building block of nucleic acids.
Option (4) Amino Acid — Incorrect. An amino acid has an –\( \ce{NH2} \) and a –COOH group, neither of which is present here.
NCERT (2026-27 edition):
Structure of Nucleic Acids
