What is Nucleoside?

What is Nucleoside?

Nucleoside: A nucleoside is formed when a pentose sugar (Ribose or De-oxy-ribose) is added with a nitrogen base (Adenine, Guanine, Thymine, Cytosine, Uracil)

Nucleoside may be of different types on the basis of sugar and bases:

  • Ribose sugar + Guanine = Guanosine
  • Ribose sugar + Adenine = Adenosine
  • Ribose sugar + Cytosine = Cylidine
  • Ribose sugar + Uracil = Uradine


When deoxyribose is the pentose sugar the nucleosides will be of the following types:

  • Deoxyribose + Guanine = De-guanosine
  • Deoxyribose + Adenine = De- adenosine
  • Deoxyribose + Cytosine = De- cytidine
  • Deoxyribose + Thymine = De-thymidine

It is clear from the above statement that both ribose and deoxyribose unite with purine bases, such as-adenine and guanine and pyrimidine base, such as- cytosine. The fourth pyrimidine base is different for both ribose and deoxyribose sugar. Ribose sugar unites with uracil but deoxyribose unites with thymine.