The primary components of a nucleotide include a sugar, a phosphate group, and a nitrogenous base. The sugar can be either ribose or deoxyribose, depending on whether the nucleotide is part of RNA or DNA, respectively. The nitrogenous base can be classified into two groups: purines (adenine and guanine) and pyrimidines (cytosine, thymine, and uracil). Nucleotides are fundamental units of nucleic acids and play critical roles in cellular functions, including energy transfer (as in ATP) and the storage and transmission of genetic information.