BIOMOLECULES AND ENZYMES

Detailed explanation-1: -All purines are nitrogen bases present in DNA and RNA that posses double ring structures. The purines present are adenine and guanine. So, the correct option is ‘Adenine’.

Detailed explanation-2: -The purines (adenine and guanine) have a two-ringed structure consisting of a nine-membered molecule with four nitrogen atoms, as you can see in the two figures below.

Detailed explanation-3: -The nitrogenous bases adenine (A) and guanine (G) are the purines; they have a double-ring structure with a six-carbon ring fused to a five-carbon ring. The pyrimidines, cytosine (C) and thymine (T), are smaller nitrogenous bases that have only a six-carbon ring structure. Figure 22.2.

Detailed explanation-4: -Adenine (A) and guanine (G) are double-ringed purines, and cytosine (C) and thymine (T) are smaller, single-ringed pyrimidines.

Detailed explanation-5: -Guanine Structure Guanine consists of two rings attached to each other: a five membered ring and a six membered ring. The five membered ring has two nitrogen atoms and three carbon atoms. One nitrogen atom is bonded to the two carbon atoms, which are also part of the five membered ring, and a hydrogen.