Which occurs in a pyrimidine, but not in a purine?
A) Two nitrogens in a six-sided ring
B) A double-bonded pair of carbon atoms in a six-sided ring
C) Two carbonyl groups as part of a six-sided ring
D) An amino group bonded to a six-sided ring
E) A five-sided ring fused to a six-sided ring

Question

Quizplus · Accepted Answer

Pyrimidines, such as cytosine, thymine, and uracil, have a single six-membered ring structure with two carbonyl groups (C=O) as part of the ring. Purines, like adenine and guanine, have a six-membered ring fused to a five-membered ring but do not have two carbonyl groups in their structure.

Which Occurs in a Pyrimidine, but Not in a Purine