Question: what is the difference between the 2 groups of nucleotides?
Answer: Nucleoside vs. Nucleotide. A nucleoside consists of a nitrogenous base covalently attached to a sugar (ribose or deoxyribose) but without the phosphate group. A nucleotide consists of a nitrogenous base, a sugar (ribose or deoxyribose) and one to three phosphate groups.