Introduction to 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 to Nucleotides
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 in to genes, fundamental unit of genetic information
Components of Nucleic acid
• Nucleic acid are the polymers of nucleotides, held by Phosphate Bridge
• Nucleotides: it 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 whereas 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 purine and pyrimidines
• 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 momnosaccharides are found in nucleic acid
• RNA contains D-Ribose while DNA contains D- deoxyribose
• Ribose and deoxyribose differe in structure at C2
D- Ribose
D-2-Deoxyribose
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 covelent bond in purine nucleotide
• In case of pyrimidines, glycosidic linkage is between N1 of pyrimidine and C1 of pentose
• The hydroxyl groupadenosine are esterified with phosphate to produce 5l or 3l monophosphate. 5l hydroxyl is most commonly esterified
• Thus AMP represents adenosine 5l 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
Biological functions of nucleotides
• Building blocks of nucleic acids (DNA and RNA).
• Involved in energy storage, muscle contraction,
• Active transport, maintenance of ion gradients.
• Activated intermediates in biosynthesis (e.g: UDP-glucose, S- adenosyl methionine)
• Components of coenzymes (NAD+, NADP+, FAD, FMN and CoA)
• Metabolic regulators:
a. Second messengers (cAMP, cGMP)
b. Phosphate donors in signal transduction (ATP)
c. Regulation of some enzymes via adenylation and uridylylation
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 the main types of nucleic acids?
- DNA and RNA are the two primary types of nucleic acids found in living organisms.
- What are the key components of nucleotides?
- Nucleotides consist of a sugar molecule, a phosphate group, and a nitrogenous base.
- What are the biological functions of nucleotides?
- Nucleotides serve as building blocks of nucleic acids, energy carriers, and cellular signaling molecules.
- How are nucleotides named?
- Nucleotides are named based on their components and structure, following standard conventions in biochemistry.
- What is the difference between a nucleotide and a nucleoside?
- A nucleotide contains a phosphate group, while a nucleoside does not. Nucleotides are involved in nucleic acid synthesis, energy metabolism, and signaling, whereas nucleosides serve as precursors for nucleotide synthesis.
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