A molecule consisting of a nitrogenous base chemically linked to a five-carbon sugar, without a phosphate group.
A nucleoside consists of two components: a nitrogenous base and a sugar such as ribose or deoxyribose. When one or more phosphate groups are added, the molecule becomes a nucleotide.
Nucleosides and their derivatives have important roles in biology. For example, adenosine is a nucleoside, while ATP (adenosine triphosphate) is a nucleotide containing three phosphate groups.
QUICK FACT
The simplest distinction is: nucleoside = base + sugar; nucleotide = base + sugar + phosphate(s).
COMMONLY CONFUSED WITH
- Nucleotide: a nucleoside with one or more phosphate groups attached.
- Nucleic acid: a chain of nucleotides forming DNA or RNA.
SEE ALSO