Question: what are the three types of nucleotides?
Answer: Nitrogenous Base. Purines and pyrimidines are the two categories of nitrogenous bases. Adenine and guanine are purines. ... 
Pentose Sugar. In DNA, the sugar is 2'-deoxyribose. In RNA, the sugar is ribose. ... 
Phosphate Group. A single phosphate group is PO43-. The phosphorus atom is the central atom.