Understanding Nucleic Acids: Structure, Composition, and Role in Biochemical Processes, Lecture notes of Biological Systems

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Macromolecule :

Nucleic acid

(Part 1 of 2) Presented by : Lucia Dhiantika Witasari

Overview

1. Structure of Nucleic Acids

2. DNA structure

3. RNA structure

4. Nucleic acid biosynthesis (Part 2)

Structure of Nucleic Acids : DNA and RNA composed of nucleotides monomers

• Nucleic acids are polymers of nucleotides, joined together by phosphodiester linkages between the 5’- hydroxyl group of one pentose and the 3’- hydroxyl group of the next.
• Two types of nucleic acid : DNA (deoxyribonucleic acid) and RNA (ribonucleic acid), are the principal information-carrying molecules of the cell.
• Nucleotides consist of
  • Nitrogeneous base
    • Purine: adenine (A), guanine (G)
    • Pyrimidine: cytosine (C), uracil (U), thymine (T)
  • Sugar : Pentose
    • Ribose
    • Deoxy-ribose
  • One or more phosphate groups

Nitrogenous Bases

• Planar, aromatic, and heterocyclic
• Derived from purine or pyrimidine
• In nucleic acids and nucleotides, nitrogen 9 of purines and nitrogen 1 of pyrimidines (red) are bonded to the 1’ carbon of ribose or deoxyribose.
• U is only in RNA, and T is only in DNA.
• Both RNA and DNA contain A, G, and C.

Nucleoside vs Nucleotide

• Cells and extracellular fluids in organisms contain small concentrations of nucleosides, combinations of a base and a sugar without a phosphate.
• Nucleotides are nucleosides that have one, two, or three phosphate groups esterified at the 5’ hydroxyl.
• Nucleoside monophosphates have a single esterified phosphate, diphosphates contain a pyrophosphate group, and triphosphates have a third phosphate. ATP

Nucleotide and nucleic acid nomenclature

Role of Nucleotides in Biochemical Processes

• Precursors of DNA and RNA.
• Activated intermediates in many biosyntheses: e.g UDP-glucose: precursor for glycogen, CDP-diacylglycerol: precursor phosphoglycerides, S- adenosylmathionine as methyl donor, etc.
• Nucleoside triphosphates, especially ATP, as the universal currency of energy in biological systems.
• Adenine nucleotides are components of the coenzymes, NAD(P)
  • , FAD, and CoA.
• Metabolic regulators: (a) c-AMP is the mediator of hormonal actions; (b) ATP- dependent protein phosphorylation - activates phosphorylase and inactivates glycogen synthase; (c) adenylation of a Tyr of bacterial glutamine synthetase - more sensitive to feedback inhibition and less active; (d) allosteric regulator - glycogen phosphorylase activated by ATP and inactivated by AMP.

Chemical energy

Component of cofactor

Homework

Write down the chemical structures of:

• AMP and dAMP
• GTP and dGTP
• CTP and dCTP
• dTTP
• UTP

The pathway from DNA to Protein

The discovery of the structure of DNA by

Watson and Crick in 1953