Guanine

Summary

Guanine, abbreviated as the letter G, is a nitrogenous base that serves as a building block for nucleotides found in both DNA and RNA. Guanine’s chemical structure contains two fused rings, meaning that it belongs to the purine family of double-ringed, nitrogen-containing bases. Guanine’s molecular structure is composed of one five-membered and one six-membered nitrogenous ring that have been fused together. Branching out from the six-membered ring is an amino group, located at the second position, and a carbonyl group, located at the sixth position. Guanine is also the heaviest nucleobase by molecular weight.

Key Points

• Guanine (G)
  • 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
      • Guanosine is a nucleoside with guanine as its base
      • Guanosine monophosphate (GMP), guanosine diphosphate (GDP), and guanosine triphosphate (GTP) are all nucleotides with guanine as their base
    • Component of DNA and RNA
  • Structure
    • Chemical Formula = C5H5N5O
    • 
    • Purine
      • Contains 2 fused rings
      • Six-membered ring fused to a five-membered ring
    • Functional Groups
      • Amino (–NH2)
        • Located at 2nd position
      • Carbonyl (–C=O)
        • Located at 6th position
        • Important in differentiating vs. Adenine
    • Heaviest of the 5 nitrogenous bases seen in DNA and RNA