QUICK ANSWER: Nucleosides and nucleotides fundamentally differ in their chemical composition. The main difference between nucleosides and nucleotides is the presence of phosphate groups. Nucleosides consist of a nitrogenous base and a sugar molecule, while nucleotides consist of these two components along with one or more phosphate groups.
Nucleosides and nucleotides are organic compounds, essential building blocks of nucleic acids, such as DNA and RNA. A nucleoside consists of two components: a nitrogenous base and a sugar molecule. The nitrogenous base can be adenine (A), guanine (G), cytosine (C), thymine (T), or uracil (U). The sugar molecule in RNA is typically a five-carbon sugar called ribose, while in DNA it is called deoxyribose. The nitrogenous base is attached to the sugar molecule through a glycosidic bond. Examples of nucleosides include Adenosine, guanosine, cytidine, uridine, and thymidine.
A nucleotide consists of three components: a nitrogenous base, a sugar molecule, and one or more phosphate groups. Nucleotides are formed when a phosphate group is attached to the 5′ carbon of the sugar molecule in a nucleoside. The number of phosphate groups can vary, with one phosphate group referred to as a monophosphate, two called a diphosphate, and three as a triphosphate. Nucleotides are named based on the nucleoside they are derived from, followed by the number of phosphate groups. For example, adenosine triphosphate (ATP) is derived from the nucleoside adenosine.
The addition of phosphate groups to nucleosides in nucleotides is essential for their role in cellular processes. Nucleotides are the building blocks for the synthesis of DNA and RNA strands. They are also involved in energy transfer and storage, cell signaling, and enzymatic reactions within the body. The presence of phosphate groups in nucleotides allows them to form phosphodiester bonds between adjacent nucleotides, which create the backbone of DNA and RNA molecules.
| Molecule | Composition | Function & Examples |
|---|---|---|
| Nucleoside | Base + Sugar | Precursors, DNA synthesis, Signaling (e.g., adenosine). |
| Nucleotide | Base + Sugar + Phosphate | DNA/RNA structure, Energy transfer (e.g., ATP), Signaling. |
Nomenclature Nucleosides and Nucleotides
Naming nucleosides and nucleotides might initially sound complicated, but the rules are pretty straightforward. A nucleoside is simply the combination of a base with a sugar; its name depends on the base type. If the base is a purine (adenine or guanine), the name ends with –osine (like adenosine or guanosine). If it’s a pyrimidine (cytosine, thymine, or uracil), the name ends with –idine (like cytidine, thymidine, or uridine). When the sugar is deoxyribose—as in DNA—the word “deoxy–” gets added at the beginning, giving names like deoxyadenosine. Once you attach phosphate groups at the 5′ carbon, the nucleoside becomes a nucleotide, and the name changes depending on how many phosphates are there: one for a monophosphate (NMP), two for a diphosphate (NDP), and three for a triphosphate (NTP).
| Nucleoside | Nucleotide (monophosphate ) | Nucleotide (diphosphate) | Nucleotide (triphosphate) |
|---|---|---|---|
| Adenosine | Adenosine monophosphate (AMP) | Adenosine diphosphate (ADP) | Adenosine triphosphate (ATP) |
| Guanosine | Guanosine monophosphate (GMP) | Guanosine diphosphate (GDP) | Guanosine triphosphate (GTP) |
| Cytidine | Cytidine monophosphate (CMP) | Cytidine diphosphate (CDP) | Cytidine triphosphate (CTP) |
| Uridine | Uridine monophosphate (UMP) | Uridine diphosphate (UDP) | Uridine triphosphate (UTP) |
| Thymidine | Thymidine monophosphate (TMP) | Thymidine diphosphate (TDP) | Thymidine triphosphate (TTP) |
This article was reviewed for accuracy by Dr. Mosayeb Rostamian. The content is based on current scientific evidence and is intended for educational purposes only.
Sources
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- Jensen, Kaj Frank, et al. “Nucleotides, Nucleosides, and Nucleobases.” EcoSal Plus, edited by Valley Stewart, vol. 3, no. 1, Jan. 2008, p. 10.1128/ecosalplus.3.6.2. https://doi.org/10.1128/ecosalplus.3.6.2.
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Squires, Kathleen E. “An Introduction to Nucleoside and Nucleotide Analogues.” Antiviral Therapy, vol. 6, no. 3_suppl, Apr. 2001, pp. 1–14. DOI.org (Crossref), https://doi.org/10.1177/135965350100603S01.
