What is the structure of nucleosides?

Medical Advisory BoardAll articles are reviewed for accuracy by our Medical Advisory Board
Educational purpose only • Exercise caution as content is pending human review
Article Review Status
Submitted
Under Review
Approved

Last updated: January 28, 2026 • View editorial policy

Personalize

Help us tailor your experience

Which best describes you? Your choice helps us use language that's most understandable for you.

Structure of Nucleosides

Nucleosides are glycosylamines composed of a nitrogenous base (purine or pyrimidine) linked through a glycosidic bond to a pentose sugar—either ribose (in RNA) or deoxyribose (in DNA). 1

Core Structural Components

Sugar Moiety

  • Ribonucleosides contain a pentose sugar ribose with a 2'-hydroxyl group 2
  • Deoxyribonucleosides (found in DNA) contain deoxyribose with a 2'-hydride instead of the 2'-hydroxyl group 2
  • The presence or absence of this 2'-OH group is the critical structural difference between RNA and DNA nucleosides 2

Nitrogenous Bases

Nucleosides contain either:

  • Purine bases: adenine and guanine 3
  • Pyrimidine bases: cytosine, thymine (DNA), and uracil (RNA) 3

Glycosidic Linkage

  • The nitrogenous base connects to the sugar through a glycosidic linkage at the 1' carbon of the sugar 1
  • This bond formation creates the nucleoside structure that serves as the foundation for nucleotides 3

Structural Significance

Chemical Stability

The 2'-hydroxyl group in ribonucleosides makes RNA approximately 100,000-fold less stable than DNA under physiological conditions 2. This occurs because the 2'-OH group facilitates nucleophilic attack on the adjacent 3'-phosphorus center through trans-esterification, leading to cleavage of 3'-5' phosphodiester bonds 2.

Biological Function

  • Nucleosides are phosphate esters that become nucleotides when phosphorylated 3
  • They serve as monomeric units of DNA and RNA and function in all cellular processes 3
  • Nucleosides are hydrophilic molecules requiring specialized transporter proteins for membrane crossing 4

Modified Nucleoside Structures

Carbocyclic Nucleosides

  • The furanose ring oxygen is replaced by a CH2 group 5
  • This modification increases flexibility and resistance to phosphorylases 5
  • Examples include neplanocins and entecavir 5

Acyclic Nucleosides

  • These lack the complete sugar ring structure 6, 7
  • Acyclovir is a synthetic purine nucleoside analogue with the chemical name 2-amino-1,9-dihydro-9-[(2-hydroxyethoxy)methyl]-6H-purin-6-one 6
  • The acyclic structure provides antiviral activity while maintaining selective enzyme affinity 6, 7

References

2
Guideline

Guideline Directed Topic Overview

Dr.Oracle Medical Advisory Board & Editors, 2025

3
Research

The biochemistry and physiology of nucleotides.

The Journal of nutrition, 1994

7
Research

Acyclic nucleosides as antiviral compounds.

Molecular biotechnology, 1996

Related Questions

What is the best treatment for a patient with a runny nose, considering potential underlying conditions such as allergies or bacterial infection?
What is the best treatment approach for a patient experiencing post cerebrospinal fluid (CSF) leak headaches?
What is the recommended approach to managing headaches in patients with varying medical histories, including potential underlying causes such as trauma, stress, hypertension, or sinusitis?
What is the pathogenesis of anterior pelvic tilt?
What is the approach to managing a patient with DRESS (Drug Reaction with Eosinophilia and Systemic Symptoms) syndrome due to anti-tuberculosis (anti-TB) medication?
What is the next step for pain management in an elderly male patient with acute right-sided back pain, retrolisthesis of L2 on L3, and moderate degenerative disc disease, who has tried a topical cream and a single dose of pain medication and muscle relaxant, is allergic to certain pain medications, and is currently on a lidocaine (lidocaine) patch, medications for anxiety, depression, and another condition, and has impaired renal function or potential gastrointestinal disease is not mentioned but needs to be considered?

Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

Have a follow-up question?

Our Medical A.I. is used by practicing medical doctors at top research institutions around the world. Ask any follow up question and get world-class guideline-backed answers instantly.

Ask Question