DNA is a nucleic acid, which is a macromolecule that is comprised of phosphate compounds, pentose compounds and bases. In DNA, the bases are aromatic, cyclic compounds. The combination of a base and a pentose compound is a nucleoside, which becomes a nucleotide when combined with phosphate.
The bases found in a DNA molecule are either purines or pyrimidines. The purines are adenine and guanine, while the pyrimidines are cytosine and thymine. The pentose found in DNA is 2-deoxyribose, which is a sugar compound. DNA macromolecules are held together by hydrogen bonds between the nucleotides, which twist in a double helical pattern.