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: -Purines (adenine and guanine) are two-carbon nitrogen ring bases while pyrimidines (cytosine and thymine) are one-carbon nitrogen ring bases. Given below in a tabular column are the differences between Purines and Pyrimidines.

Detailed explanation-3: -Purine bases include adenine (6-aminopurine) and guanine (2-amino-6-oxypurine) (Fig. 6.3).

Detailed explanation-4: -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-5: -Purines. Adenine and guanine are found in both DNA and RNA. Hypoxanthine and xanthine are not incorporated into the nucleic acids as they are being synthesized but are important intermediates in the synthesis and degradation of the purine nucleotides.