Nucleic Acids
• Nucleic acids are large biomolecules (polymers) –
essential for all known forms of life
• Include DNA and RNA
• Made from long strands of nucleotides
(monomers)
– A nucleotide contains a 5-carbon sugar, a phosphate
group, and a nitrogenous base
– The nitrogeneous bases are connected by the sugar
and the phosphate group (rungs of the ladder)
DNA vs. RNA
• If the sugar molecule is Deoxyribose, the
nucleic acid is DNA
• If the sugar molecule is Ribose, the nucleic
acid is RNA
• RNA – mRNA, tRNA, rRNA
Purines vs Pyrimidines
Purines have a 2-Carbon nitrogen ring base
Adenine
Guanine
Pyrimidines have a 1-carbon nitrogen ring base
Thymine
Cytosine
Nitrogeneous Bases
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•
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•
•
Adenine
Thymine (DNA only)
Cytosine
Guanine
Uracil (RNA only)
Base Pairing
• The rules of base pairing (or nucleotide
pairing) are: A with T: the purine adenine (A)
always pairs with the pyrimidine thymine (T)
• C with G: the pyrimidine cytosine (C) always
pairs with the purine guanine (G)
• The bases are paired with hydrogen bonds – 2
between A and T and 3 between C and G