The three components of a nucleotide are the nitrogenous base, the five-carbon sugar and the phosphate group. In turn, the nucleotides are the building components of both DNA and RNA.
The nitrogenous base molecules in DNA are the amino acids adenine, thymine, guanine and cytosine, while in RNA the guanine is replaced with uracil. The sugar molecules are different in the nucleotides of DNA and RNA; they are 2-deoxyribose and ribose, respectively. The final molecular component of the nucleotide is the phosphate group, or in some cases up to three phosphate groups. In addition to being the subunit of DNA and RNA, nucleotides are also important in cell metabolism, cell signaling, enzymatic reactions and the transfer of energy within a cell.