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 2nd 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 pH 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 5l or 3l 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)
- What are nucleic acids? Nucleic acids are macromolecules that store and transmit genetic information in living organisms.
- 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.
- How does DNA replication work? DNA replication involves the precise copying of DNA to ensure accurate transmission of genetic information during cell division.
- 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.
- 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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