BIOMOLECULES AND ENZYMES

Detailed explanation-1: -The purines in DNA are adenine and guanine, the same as in RNA. The pyrimidines in DNA are cytosine and thymine; in RNA, they are cytosine and uracil. Purines are larger than pyrimidines because they have a two-ring structure while pyrimidines only have a single ring.

Detailed explanation-2: -In DNA, guanine and adenine base pair (see Watson-Crick pairing) with cytosine and thymine (see pyrimidines) respectively. Adenine is also found in adenosine triphosphate (see ATP) and other coenzymes. Two other important biological purines are hypoxanthine and xanthine.

Detailed explanation-3: -The chemical structures of A, G, C, T, and U are shown in (Fig. 1.5A). Because of their structural similarity, we usually refer the nine-member double rings adenine and guanine as purines, and six-member single-ring thymine, uracil, and cytosine are pyrimidines.

Detailed explanation-4: -DNA contains two purines, adenine and guanine, which are rings composed of six parts. These bases form hydrogen bonds with their complementary pyrimidines, thymine and cytosine, respectively.

Detailed explanation-5: -A chemical compound that is used to make one of the building blocks of DNA and RNA. It is also a part of many substances in the body that give energy to cells. Adenine is a type of purine.