Question

What are the positions of 'N' atoms present in purine ring of nucleic acids?

• A. 1, 3 and 5
• B. 1, 3 and 9
• C. 1, 5, 7 and 9
• D. 1, 3, 7 and 9

Hint:

Purine bases (Adenine, Guanine) attach to the sugar molecule specifically via the Nitrogen at position 9 (N-9 glycosidic linkage). Pyrimidines attach via the Nitrogen at position 1.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
Purines (Adenine and Guanine) are heterocyclic aromatic organic compounds consisting of a pyrimidine ring fused to an imidazole ring.

Step 2: Formula Application:
Refer to the standard numbering of the purine bicyclic system.

Step 3: Explanation:
In the purine skeleton, Nitrogen atoms are located at positions 1 and 3 (in the six-membered ring) and positions 7 and 9 (in the five-membered ring).

Step 4: Final Answer:
The nitrogen positions are 1, 3, 7, and 9.