Cytosine

Summary

Cytosine, abbreviated as the letter C, is a nitrogenous base that serves as a building block for nucleotides found in both DNA and RNA. Cytosine’s structure contains only one six-membered ring, meaning that it belongs to the pyrimidine family of one-ringed, nitrogen-containing bases. Branching out from this one central ring are two functional groups: a carbonyl at the 2nd position and an amino group at the 4th position. Cytosine is also the lightest nucleobase by molecular weight.

Key Points

• Cytosine (C)
  • Characteristics
    • Nitrogenous Base
      • Organic molecules made up of nitrogen-containing ring structures
      • Each base has a unique structure, with its own set of functional groups attached to the ring structure 
    • Building block of Nucleosides and Nucleotides
      • Cytidine is a nucleoside with cytosine as its base
    • Component of DNA and RNA
  • Structure
    • Chemical Formula = C4H5N3O
    • 
    • Pyrimidine
      • Contains 1 ring (six-membered)
    • Functional Groups
      • Carbonyl (–C=O)
        • Located at 2nd position
      • Amino (–NH2) 
        • Located at 4th position
        • Important in differentiating vs. thymine and uracil
    • Lightest of the 5 nitrogenous bases seen in DNA and RNA