This nucleotide contains: the five-carbon sugar deoxyribose (at center), a nitrogenous base called adenine (upper right), and one phosphate group (left). The whole structure along with the phosphate group is a nucleotide, a constituent of DNA.

A nucleotide is an organic molecule. Nucleotides are the building blocks of the nucleic acids RNA and DNA. These two types of nucleic acid are essential biomolecules in all forms of life on Earth.

A nucleotide is composed of a nucleobase (nitrogenous base), a five-carbon sugar (either ribose or 2-deoxyribose), and one phosphate group. Nucleotides contain either a purine or a pyrimidine base. Ribonucleotides are nucleotides in which the sugar is ribose. Deoxyribonucleotides are nucleotides in which the sugar is deoxyribose.