1. Pyrimidines and Purines Pyrimidine and purine are the names of the parent compounds of two types of nitrogen- containing heterocyclic aromatic compounds. N N N N N NH PyrimidinePurine

2. Important Pyrimidines Pyrimidines that occur in DNA are cytosine and thymine. Cytosine and uracil are the pyrimidines in RNA. HNHNHNHN NHNHNHNHOO Uracil HNHNHNHN NHNHNHNHOO CH 3 Thymine HNHNHNHN NHNHNHNH NH2NH2NH2NH2 O Cytosine

3. Important Purines Adenine and guanine are the principal purines of both DNA and RNA. Adenine N N NH2NH2NH2NH2N NHNHNHNH GuanineO HNHNHNHN NHNHNHNH N N H2NH2NH2NH2N

4. Caffeine and Theobromine Caffeine (coffee) and theobromine (coffee and tea) are naturally occurring purines. Caffeine N NON N H3CH3CH3CH3C O CH 3 TheobromineO HNHNHNHN N N N O

5. 27.24 Nucleosides

6. Uridine and Adenosine Uridine and adenosine are pyrimidine and purine nucleosides respectively of D -ribofuranose. Uridine (a pyrimidine nucleoside) Adenosine (a purine nucleoside) N N N N HOCH 2 O OHHO NH2NH2NH2NH2

7. 27.25 Nucleotides

8. Nucleotides Nucleotides are phosphoric acid esters of nucleosides.

9. Adenosine 5'-Monophosphate (AMP) Adenosine 5'-monophosphate (AMP) is also called 5'- adenylic acid. N N N N O OHHO NH2NH2NH2NH2 OCH 2 P HO O HO

10. Adenosine 5'-Monophosphate (AMP) Adenosine 5'-monophosphate (AMP) is also called 5'- adenylic acid. N N N N O OHHO NH2NH2NH2NH2 OCH 2 P HO O HO 1' 2'3' 4' 5'

11. Adenosine Diphosphate (ADP) N N N N O OHHO NH2NH2NH2NH2 OCH 2 P O O HO P O HO HO

12. Adenosine Triphosphate (ATP) N N N N O OHHO NH2NH2NH2NH2 OCH 2 P O O HO P O HO O P O HO HO

13. Adenosine 3'-5'-Cyclic Monophosphate (cAMP) Cyclic AMP is an important regulator of many biological processes. N N N N O OHO NH2NH2NH2NH2 CH 2 P O HO O

14. 27.26 Nucleic Acids

15. Nucleic Acids Nucleic acids are polymeric nucleotides (polynucleotides). 5' Oxygen of one nucleotide is linked to the 3' oxygen of another.

16. Fig. 27.22 A section of a polynucleotide chain.