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Chapter 4

BLG 143 Chapter 4: Chapter 4 – Nucleic Acids and the RNA world

Course Code
BLG 143
Vadim Bostan

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Chapter 4 Nucleic Acids and the RNA world.
4.1 What is a Nucleic Acid?
Nucleic acids are polymers; the subunit or monomer of a nucleic acid are called nucleotides.
These nucleotides are composed of a phosphate group, a sugar and a nitrogenous base. Sugar is
an organic compound with a carbonyl group and several hydroxyl groups.
Ribonucleotide - ribose sugar
Deoxyribose Nucleotide - deoxyribose sugar
These two differ in the way that ribonucleotide has an –OH oded to the ’ ao ad
deoiose has a H oded to the ’ ao.
Nitrogenous Bases: Adenine (A), Guanine (G), Cytosine (C), Thymine (T) and Uracil (U)
Uracil is found in RNA and Thymine is found in DNA
Purines: Adenine, Guanine (double ringed)
Pyrimidines: Cytosine, Thymine and Uracil (single ringed)
Nucleic acids form when nucleotides polymerize. Phosphodiester linkage is the bonding
between nucloetides (polymerization). Polymeriztion is endergonic. Phosphorylated is the
addition of a phosphate molecule. This raises the potential energy of the substrate molecule
enough to allow an endergonic reaction to occur.
DNA strands run anti parallel. One end of the sugar phosphate akoe has a fee 5’
ao ad the othe ed has a fee ’ ao. These seuees ae alas itte fo 5’ to
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