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NUCLEIC ACIDS

Nucleic acids are long chain polymers (actually macromolecules as they consist of four types
of nucleotides and they are not repeated in an orderly manner) of nucleotides (monomers).
Each nucleotide is made up of a sugar (either ribose or deoxy-ribose), a base (thymine,
cytosine, uracil, adenine or guanine) and a phosphate group (where the sugar and the base together
constitute a nucleoside) (Fig. 7.1).
Fig.7.

There are two types of nucleic acids, DNA (Deoxy-ribo Nucleic Acid) and RNA (Ribo Nucleic Acid) that differ mainly with respect to the sugar, which is 2-deoxy-ribose (C5H10O4,
where an O atom is missing at position 2 in the ring) in DNA and ribose (C5H10O5) in RNA
(Fig. 7.1 and 7.2). The sugar is found in the ring form where the phosphate is attached to the sugar
either at 3′ -OH or 5′ -OH by elimination of a molecule of water, whereas the base (pyrimidine
with N1 and purine with N9) at C1 (See Fig. 7.5).

Fig.7.2

Fig. 7.2 Structure of ribose and deoxy-ribose sugars.