The nucleotides participate in a large amount of metabolic process and they are considered nucleic acid subunits. They also participate as energy carriers (ATP is an example). Nucleotide can be also found as components enzymatic cofactors and some of them are chemical messengers.

Nucleotides have three characteristic components: a nitrogenous base, a pentose (in green - the hydroxyl group represented in violet color indicates that the represented pentose is a ribose), and a phosphate group (in blue). Without the phosphate group, the molecule is called a nucleoside.

Pyrimidine

Purine

The nitrogenous bases are derivatives of two parent compounds, purine and pyrimidine. The first one is the adenine (A) and guanine (G), and the pyrimidine are cytosine (C), thymine (T) and uracil (U).

Two kinds of pentoses are found in nucleic acids. The recurring deoxyribonucleotide units of DNA contain 2’-doexy-D-ribose, and the ribonucleotide units of RNA contain D-ribose. In nucleotides, both types of pentoses are in their ß-furanose form.

Note that nucleotides have one, two or three phosphate groups covalently linked at the 5’-hydoxyl of ribose. These are referred to as nucleoside mono-, di-, and triphosphate, respectively. Nucleoside triphosphates are used as a source of chemical energy to drive a wide variety of biochemical reactions. ATP is by far the most widely used, but UTP, GTP and CTP are used in specific reactions. Nucleoside triphosphates also serve as the actived precursors of DNA and RNA synthesis

- Basic structure of DNA and RNA

- Deoxyribonucleotides synthesis

- Nucleic Acids Catabolism

- Nucleics Acids Synthesis