What does nucleoside mean?
A nucleoside is one of the basic building blocks of DNA and RNA: a nitrogenous base joined to a five-carbon sugar. When the sugar is ribose, the molecule is a ribonucleoside; when it is deoxyribose, it is a deoxynucleoside. Nucleosides are chemically related to nucleotides, but a nucleotide additionally contains phosphate groups and can therefore participate more directly in energy transfer, signalling, and nucleic-acid construction. The word also appears in pharmacology in compounds such as nucleoside analogues, which can interfere with viral or cellular nucleic-acid metabolism. Although the term is most familiar in molecular biology, it belongs to a broader chemical vocabulary concerned with the structures and functions of biologically significant molecules. Its precise distinction from nucleotide is important in discussions of DNA, RNA, enzymes, antiviral drugs, and cellular energy metabolism.
nounA nucleoside is a molecular unit consisting of a nitrogenous base joined to a five-carbon sugar, either ribose or deoxyribose. Unlike a nucleotide, it does not contain phosphate groups.
- A chemical compound consisting of a nitrogenous base covalently linked to a pentose sugar.
"The nucleoside adenosine forms an important part of the energy molecule ATP."
"Cytidine is a nucleoside found in RNA."
"The researchers screened the library for nucleoside analogues with antiviral activity."
The plural is used when referring to multiple nucleoside molecules or to a class of compounds.
"The enzyme phosphorylates several nucleosides in the cell."
Split the word itself: a nucleoside is a “side” of the nucleus—well, more precisely, a base-and-sugar building block used to build larger molecules such as DNA and RNA.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Where does nucleoside come from?
The word was formed in the early 20th century from the combining form “nucleo-,” associated with the nucleus, together with the chemical suffix “-side.” The underlying Latin nucleus means “kernel” or “nut,” reflecting the historical association of the cell nucleus with cellular control structures. The “-side” element is used in chemical terminology for a larger or residual part of a molecule, and the related form nucleotide refers to a phosphate-containing derivative of a nucleoside.
Related word forms
How nucleoside is actually used
The term is primarily used in biochemistry, molecular biology, and pharmacology. It is distinct from “nucleotide,” which includes phosphate groups, and from “base,” which refers only to the nitrogenous component.
Easily confused with nucleoside
A nucleoside is a nitrogenous base attached to a sugar, whereas a nucleotide also contains one or more phosphate groups.