The subunit of DNA is called a nucleotide. A nucleotide is the basic subunit in a nucleic acid and consists of a pentose sugar, a phosphate and a heterocyclic amine.
Although they are best known as the building blocks of DNA, which stores and transfers an organism's genetic information, nucleotides are a part of nearly every biochemical process.
Nucleotides are present in nearly every form of life, from bacteria and viruses to humans. They carry packets of energy within a cell and play a key role in metabolism. Nucleotides also participate in cell signaling, the communication and coordinating of cell actions.
The most common bases in nucleotides are the pyridine nicotinamide, purines adenine and guanine and pyrimidines uracil, thymine and cytosine. The pentose sugar is either ribose or deoxyribose. Depending on the base sugar, nucleotides are either ribonucleotides or deoxyribonucleotides.
Chemistry sources such as the ACS Style Guide state that the term nucleotide only refers to a molecule that contains one phosphate. Common usage in molecular biology textbooks, however, often extend the definition to include molecules that have two or three groups of phosphates. Therefore, the term "nucleotide" typically refers to a nucleoside monophosphate, but nucleoside diphosphates and nucleoside triphosphates can also be considered nucleotides.