Highly simplified diagram of a double-stranded nucleic acid. Yellow circles represent phosphate; green circles represent pentose; red circles represent nitrogenous bases. Solid lines represent covalent bonds; dashed lines represent hydrogen bonds. |
Nucleic acid, so called because of its prevalence in cellular nuclei, is the generic name of family of biopolymers. The monomers are called nucleotides, and each consists of three components: a nitrogenous heterocyclic base (either a purine or a pyrimidine), a pentose sugar, and a phosphate group. Different nucleic acid types differ in the specific sugar found in their chain (e.g. DNA or deoxyribonucleic acid contains 2'-deoxyriboses).
The sugars and phosphates in nucleic acids are connected to each other in an alternating chain through shared oxygens (forming a phosphodiester functional group). Using the conventional nomenclature, the carbons to which the phosphate groups are attached are the 3' and the 5' carbons. The bases are pendant from a glycosidic linkage to the 1' carbon of the pentose ring.
Nucleic acids may be single-stranded or double-stranded. A double-stranded nucleic acid consists of two single-stranded nucleic acids hydrogen-bonded together. RNA is usually single-stranded, but any given strand is likely to fold back upon itself to form double-helical regions. DNA is usually double-stranded, though some viruses have single-stranded DNA as their genome.
Nucleic acids are primarily biology's means of storing and transmitting genetic information, though RNA is also capable of acting as an enzyme.