A nitrogenous base is attached to the pentose sugar by an N -glycosidic linkage to form a nucleoside, i.e., Nucleoside Nitrogen base + Pentose sugar. When a phosphate group is attached to the of a nucleoside through phosphodiester linkage, a nucleotide is formed, i.e., Nucleotide = Nitrogen base + Pentose sugar + Phosphate . So, a nucleoside differs from a nucleotide as it lacks the phosphate group.

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