Nucleic acids are made up of monomeric units called nucleotides. Nucleotides serve important biochemical functions as components of coenzymes involved in transferring phosphoryl, sugar, lipid groups. They also function as second messengers like cAMP and cGMP. Synthetic nucleotides containing halogens or additional nitrogen are used in chemotherapy and immunosuppression. Purines and pyrimidines are heterocyclic nitrogen-containing compounds that form the bases of nucleic acids. Nucleosides are derivatives of bases linked to a sugar, while nucleotides contain a phosphoryl group attached to the sugar. RNA and DNA are made up of ribonucleotides and deoxyribonucleotides formed through a series of phosphorylation and conversion reactions in

1. NUCLEIC ACID Structure and Functions

2. Biomedical importance Monomeric units or building blocks of nucleic acids. They form a part of many coenzymes. Donors of phosphoryl gropups (eg. ATP or GTP), of sugars (UDP- or GDP-sugars or of lipid (CDP-acylglycerol) Serve as second messengers (eg. cAMP and cGMP ) Synthetic nucleotides Synthetic purine and pyrimadine analogs containing halogens, thiols or additional nitrogen are used for : chemotherapy of cancer and AIDS Immunosuppressant for organ transplantation.

3. Purine and Pyrimidine Purines and pyrimidines are nitrogen-containing heterocycles, cyclic compounds whose rings contain both carbon and other elements (hetero atoms).

4. Sources of the individual atoms in the purine ring.

5. Under physiologic conditions, the amino and oxo tautomers of purines,pyrimidine, and their derivatives predominate.

6. Nucleosides Nucleosides are derivatives of purines and pyrimidines that have a sugar linked to a ring nitrogen. The sugar is linked to the heterocyclic base via a β -N-glycosidic bond, almost always to N-1 of a pyrimidine or to N-9 of a purine.

7. Nucleotides RNA RNA DNA DNA

8. Mononucleotides are nucleosides with a phosphoryl group esterfied to a hydrosyl group of the sugar. 3’- and 5’ –nucleotides are nucleosides with a phosphoryl group on the 3’ – or 5’ –hydroxyl group of the Sugar. Nucleotides Nucleostides are present in all type of cells.

9. Ribonucleoside monophosphate, diphosphate, and triphosphate.

10. Conversion of nucleoside mono phosphates to nucleoside di phosphates and tri phosphates.

11. Conversion of ribonucleotides to deoxyribonucleotides.

13. Cyclic AMP and GMP Adenylate cyclase

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24. Dinucleotide

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