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 (gunanine or adenine) base is attached to `C - 1` of sugar (ribose or deoxyribose) by a `beta-`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 esterifaction of `C_(5)- OH` group of the pentose sugar by phosphoric acid.
