The chemical structure of a nucleotide consists of three main components: a five-carbon sugar, a phosphate group, and a nitrogenous base. The sugar can be either ribose (in RNA) or deoxyribose (in DNA). The nitrogenous base is one of four types: adenine, thymine, cytosine, or guanine in DNA, and adenine, uracil, cytosine, or guanine in RNA. Nucleotides are the building blocks of nucleic acids and play essential roles in storing and transmitting genetic information.