What is the difference between a nucleoside and nucleotide ?
A nucleoside is formed by the attachment of purine or pyrimidine base to the 1-position of a pentose sugar.
On the other hand, a nucleotide is a unit formed by the attachment of nucleoside to phosphoric acid at the 5′-position of the sugar moiety.
A nucleoside contains only two basic components of nucleic acids i.e., a pentose sugar and a nitrogenous base. It is formed when 1- position of pyrimidine (cytosine, thiamine or uracil) or 9-position of purine (guanine or adenine) base is attached to C -1 of sugar (ribose or deoxyribose) by a β-linkage. Nucleic acids are also called polynucleotides since the repeating structural unit of nucleic acids is a nucleotide.
A nucleotide contains all the three basic . components of nucleic acids, i.e., a phosphoric acid group, a pentose sugar and a nitrogenous base. These are obtained by esterification of C5, – OH group of the pentose sugar by phosphoric acid.