Naturally occurring polymers- (nucleic acid)

Nucleic acid

These are biologically important polymers which are present in all living cells. They direct the synthesis of proteins and are responsible for transfer of genetic information i.e hereditary characteristics. The repeating unit in nucleic acids are called nucleotides. Thus the nucleic acid are basically polynucleotide. Each nucleotide is made up of three components.

1) A nitrogen containing heterocycle base which is of two types namely purines and pyrimidines.

a) The two purines are Adenine and Guanine.

Adenine.

Guanine.

b) The three pyrimidines are Cytosine, thymine and uracil.

Uracil.

Thymine.

Cytosine.

The two purines i.e Adenine and Guanine and pyrimidine Cytosine is present in both DNA and RNA. But uracil is present in RNA instead of thymine present in DNA.

2) A pentose sugar i.e either ribose or deoxyribose.

D-ribose.

D-deoxyribose.

3) A phosphate group

This group act as linkage between nucleic acid.

Phosphoric acid.

A pentose sugar at carbon 1' is linked to the nitrogen of the heterocycle base and this bond is called glycosidic bond and the compound formed is called nucleoside Fig(a). When the phosphate group is attached to ( carbon 5') of nucleoside a nucleotide is formed Fig(b) Next>>

Nucleoside.

Nucleotide.