Biology Biomolecules ETEA 2023 Retake
PMDC Verified Question 64 of 142
Purines are ____ nitrogenous bases.
A
Double ringed
B
Single ringed
C
Double bond
D
Single bond
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option A: Double ringed
Concept:

Nitrogenous bases fall into two structurally distinct families.

Solution:

  • Purines (Adenine and Guanine) are the larger, more complex nitrogenous bases.


  • They are formed by fusing a six-membered pyrimidine ring directly to a five-membered imidazole ring.


  • Because of this fused structure, they are structurally classified as Double ringed bases.


Why other options are incorrect:

  • Single ringed: Defines the Pyrimidines (Cytosine, Thymine, Uracil).


  • Single/Double bond: Both types of rings contain multiple single and double bonds; these terms do not classify the base families.

Quality & Fidelity Assurance: Every question on BeambePrep is rigorously curated against the official PMDC syllabus with zero filler, zero out-of-syllabus content, and zero typos. When an authentic past paper originally contained a historical mistake or ambiguity from the examining board (such as UHS or NUMS), BeambePrep faithfully reflects the original paper while detailing the nuance and scientific consensus in the autopsy above.

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