Viruses

Viruses

1. Structure

   • Size
     • Small
       • 20nm (polio)
       • 300nm (pox)
   • Shape
   • Genetic material enclosed in a capsid
     • Nucleic Acid
       • DNA
         • Linear or circular
           • ss DNA e.g Parvoviridae
           • ds DNA e.g Herpesviridae
       • RNA
         • Linear
           • ss RNA e.g Parvoviridae
             • (+) ss RNA e.g Picornaviridae
             • (-) ss RNA e.g Paramyxoviridae
           • ds RNA e.g Reoviridae
     • Capsid
       • Protein coat
       • Made up of protein sub units called capsomeres
       • Gives the virus it shape
         • Helical
         • Icosahedral
         • Complex
   • Envolope or Naked
     • Envoloped
       • Lipid bilayer surrounding capsid
         • Made of host cell lipids
         • Surface proteins called glycoproteins
           • Used to attach to host cell
           • Can cause hemagglutination e.g influenza
     • Non-envoloped
       • No lipid bilayer (naked)

2. Replication

   • Cant replicate outside a host cell
     • Completly dependant on host cells for replication
       • Replicate at a fast rate
   • Can mutate
   • Don't grow or divide
     • New viral components are synthesized and assembled within the infected host cell