Functions of the capsid

• 1. protects enclosed nucleic acid from physical destruction and enzymatic hydrolysis by host cell nucleases.
  2. gives shape
  3. for attachment
  4. with antigenic specificity which determines the type of cell, the virus can infect.
• Envelope - an outer membranous layer that surrounds some viruses made of lipids, glycoprotein, and protein.
• Shape - symmetrical, helical, spheres, cylinders, wedges, or prism.

  Ex:

  • tobacco or cucumber mosaic virus - long, thin rods.
• Bacteriophage - spherical with tail-like appendages.
• Influenza virus - rods, filaments as well as spheroids.
• naked virions - those without envelope.
• Icosohedral - regular polyhedral with 20 triangular faces and 12 corners.