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DNA Bases

DNA is composed of phosphate, a sugar and 4 nitrogenous bases. These bases are Adenine,
Thymine, Cytosine and Guanine. They are organic molecules that have a large amount of
nitrogen contained within them that is relative to their overall mass and are proton acceptors
that tend to carry a net positive charge.
Adenine and Guanine are classified as purines while Thymine and Guanine are pyrimidines
which are all non-polar and planar molecules. Purines are six membered rings fused to a
five-member ring and between them, the rings include 4 nitrogen atoms and five carbon atoms.
On the other hand, pyrimidines have only a six-membered ring which has two nitrogen atoms
and four carbon atoms. Each base also has other constituents projecting from the ring. These
bases are bonded together in pairs and due to the large structure of purines and the small
structure pyrimidines, they are bonded opposite to each other and therefore Adenine is bonded
to Thymine and Cytosine is bonded to Guanine. They are bonded together with hydrogen
bonds: Adenine and Thymine having one H-N and one H-O bond while Cytosine and Guanine
have two H-N and one H-O bond.
Represented by the letter A, its chemical formula is C5H5N5.
Represented by the letter G, its chemical formula is C5H5N5O.
Represented by the letter T, its chemical formula is C5H6N2O2.
Represented by the letter C, its chemical formula is C4H4N2O2.
Nucleotides vs Nucleosides
Nucleotides and nucleosides are structurally similar molecules, only having one small
difference. Although the difference is small, it causes a difference in their functions.
Nucleotides are molecules made up of a sugar, nitrogenous base and phosphate while
nucleosides are made up of just a sugar and nitrogenous base.
Nucleotides polymerize and form nucleic acids as well as act like energy storing molecules while
nucleosides are anticancer compounds that have antiviral properties.