A nucleotide (nucleoide phosphate) is a compound formed by the union of a nitrogen base, a pentose sugar and a phosphate. The nitrogen base combines with the sugar molecule at its carbon atom 1′ in glycosidic bond (C - N - C) by one of its nitrogen atoms (usually 1 in pyrimidines and 9 in purines). The resulting structure is known as a nucleoside. Nucleotide is formed through phosphorylation of nucleoside. Phosphate combines with sugar molecule at its 5’ carbon atom to form a nucleotide.