Nitrogenous Bases: Purines & Pyrimidines — NEET Biology
✅ Asked in NEET 2022As you notice in, the heterocyclic compounds in nucleic acids are the nitrogenous bases named adenine, guanine, uracil, cytosine, and thymine. Adenine and Guanine are substituted purines while the rest are substituted pyrimidines. The skeletal heterocyclic ring is called as purine and pyrimidine respectively. The sugar found in polynucleotides is either ribose (a monosaccharide pentose) or 2' deoxyribose. A nucleic acid containing deoxyribose is called deoxyribonucleic acid (DNA) while that which contains ribose is called ribonucleic acid (RNA).
NTA tests whether students correctly classify nitrogenous bases as purines or pyrimidines. Adenine and guanine are purines (two-ring structures), while thymine, cytosine, and uracil are pyrimidines (single-ring structures). The common mistake is confusing which bases belong to which category or forgetting that adenine and guanine specifically are purines despite their different names. Remember: Purines are larger (double-ring) and include Adenine and Guanine; pyrimidines are smaller (single-ring). This distinction is fundamental because it affects base-pairing rules (A pairs with T/U, G pairs with C) and distinguishes DNA from RNA molecules.
Match List-I with List-II (NEET 2022 Phase 2) List I A. Adenine B. Anthocyanin C. Chitin D. Codeine List II i. Pigment ii. Polysaccharide iii. Alkaloid iv. Purine Choose the correct answer:
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