Nucleic acids and Nucleotides

Nucleic acids and Nucleotides

Objective

–      At the end of this lecture, student will be able to

–      Explain the types of nucleic acid and their components

–      Discuss the biological functions of nucleotides

–      Describe the nomenclature of nucleotides

–      Distinguish between nucleotide and nucleoside

Introduction

•       Two types of nucleic acid – DNA & RNA

•       It serves as transmitter of genetic information

•       DNA is a chemical basis of heredity and regarded as the reserve bank of genetic information

•       It is responsible for the maintaining the identity of different species of organism over millions of years

•       Every aspects of cell function is under the control of DNA

•       DNA is organized into genes, fundamental unit of genetic information

•       Gene control the protein synthesis

Biological functions of nucleotides

•        Building blocks of nucleic acids (DNA and RNA)

•        Important role in carbohydrate, fat and protein metabolism

•        Purine nucleotides act as high energy source ATP, cyclic AMP  in a wide variety of tissues and organisms

•        Also act as components of coenzymes (NAD, NADP, FAD)

•        Pyrimidine nucleotides act as high energy intermediates such as UDP-glucose and UDP-galactose in carbohydrate metabolism and also in lipid synthesis

Components of Nucleic acid

•       Nucleic acid are the polymers of nucleotides, held by phosphate bridge

•       Nucleotides:

                It is composed of

                                                                Nitrogen base

                                                                Pentose sugar

                                                                Phosphate

•       Nucleoside: Nitrogen base + pentose sugar

•       Thus nucleotides are nucleosides + phosphate 

•       The atom in purine ring are numbered as 1 to 9 and for pyrimidine as 1 to 6 where as pentose carbon 1 to 5

•       Nucleic acid are the polymers of nucleotides, held by phosphate bridge

Structure of Nucleotides

•       The nitrogen bases found in nucleotides are aromatic heterocyclic compounds

•       Nitrogen bases are of 2 types:

                                1. Purines:   a. Adenine

                                                         b. Guanine

                                                         These are numbered in anti-clock wise direction

                                2. Pyrimidines:   a. Cytosine

                                                                   b. Thymine

                                                                   c.  Uracil

                                                                These are numbered in clock wise direction

•       DNA & RNA contain the same purines and differ in 2^nd pyrimidine

•       Cytosine is found in both DNA & RNA , but differ in second pyrimidine., i.e. DNA → Thymine and RNA → Uracil

Nitrogen bases structures

Sugars of nucleic acid

•       The five carbon monosaccharides are found in nucleic acid

•       RNA contains D-Ribose while DNA contains D-deoxyribose

•       Ribose and deoxyribose differ in structure at C₂

Nucleic acids – Polynucleotides

•       Two types of nucleic acid – DNA & RNA- made of nucleotides

Tautomeric forms of purines and pyrimidines

•       The existence of a molecule in a keto and enol for is known as tautomerism

•       Purine & pyrimidines with oxo (-c-) functional group exhibits tautomerism

•       The lactam and lactim forms of cytosine are represented as:

•       At physiological p^H the lactam tautomeric forms are present

Nucleotides

•       Pentose are bonded to nitrogen bases by β-N-glycosidic bonds

•       N⁹ of purine ring binds with C¹ of pentose sugar to form a covalent bond in purine nucleotide

•       In case of pyrimidines, glycosidic linkage is between N¹ of pyrimidine and C¹ of pentose

•       The hydroxyl groups of adenosine are esterified with phosphate to produce 5^l or 3^l monophosphate. 5’ hydroxyl is most commonly esterified 

•       Thus AMP represents adenosine 5’-monophosphate

•       However, for Adenosine-3-monophosphate the abbreviation 3-AMP is used

•       Pentose are bonded to nitrogen bases by β-N-glycosidic bonds

•       Nucleotides of DNA

•       Nucleotides of RNA

•       Nucleotide diphosphates and triphosphates

•       Cyclic nucleotides

Summary

•       2 types of nucleic acid DNA and RNA

•        Nucleotides: nucleoside + phosphate

•        Nucleosides: Nitrogen base + pentose sugar

•        DNA & RNA contains both purines and Pyrimidines

•        Purines are Adenine and Guanine

•        Pyrimidines are cytosine, thymine and uracil

Frequently Asked Questions (FAQs)

1. What are nucleic acids? Nucleic acids are macromolecules that store and transmit genetic information in living organisms.
2. What is the difference between DNA and RNA? DNA is double-stranded and stores genetic information, while RNA is single-stranded and is involved in protein synthesis.
3. How does DNA replication work? DNA replication involves the precise copying of DNA to ensure accurate transmission of genetic information during cell division.
4. What are the medical applications of nucleic acids? Nucleic acids have paved the way for advancements in gene therapy, genetic engineering, and diagnostic tools in the field of medicine.
5. What is the future of nucleic acid research? Ongoing research in nucleic acids promises further insights into genetics and biotechnology, potentially uncovering more about the complexities of life.

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