Chapter 6

  1. Louis Pasteur
    Discovered the first vaccines for rabies.

    Proposed the term "virus"
  2. Viruses
    Unique group of biological entities known to infect every type of cell.

    • Unusual strucure and behavior
    • Infectious particles.
    • Obligate intracellular parasites
  3. Electron microscope
    You can see virus
  4. Type of viruses

  5. Capsid
    Protective outer shell that surronds viral nucleic acid.

    Capsid spikes are used for attachement to host cells.

    • 2 types of capsids.
    • -helical
    • -icosahedral
  6. Helical Capsid
    • Form a continuos helix.
    • Nucleic acids coils inside
  7. Types of Helical viruses
    • Naked Helical.
    • Enveloped helical
  8. Naked helical virus
    • -Tobacco mosaic
    • -Nucleocapsid is rigid and tighly wound into a cylinder shape package
  9. Enveloped helica virus
    • -Inglueza, measles, rabies.
    • -Nucleocapsid is more flexible.
    • -Enveloped come from host cell membrane
  10. Icosahedron Capsid
    3 dimensional.

    • -Variation in capsomer number
    • Polio virus 32 capsomer
    • Adenovirus 240 capsomer
  11. Types of Icosahedral viruses
    • -Naked icosahedral viruses.
    • Papillomavirus

    • -Enveloped Icosahedral virus.
    • Herpes.
    • Envelope como fron host cell membrane
  12. Envelope
    • -Animal viruses.
    • -Lipid and proteins.
    • -Envelope spkies fro attachament of viruses to the next host cell
    • -Enables pleomorphic shape of viruses
  13. Function of capsid/envelope
    • -Protect nucleic acid from the host's acid and protein digestive enzymes
    • -Asist in binding and penetrating host cell
    • -Stimulate the host's immune system
  14. Complex viruses
    • -Intricate structure
    • -Pox virus
    • -Bacteriophage
    • 1 virus can infect 1 cell @ the time.
    • Only the DNA gets to the cell
  15. Nuclei Acid
    • -Viruses contain either DNA or RNA but not both
    • -Posess only the genes to invade and regulate the metabolic activity of host cell
    • -No viral metabolic genes
  16. Multiplication cycle
    • - Adsoption ( Attachment):The virus attaches to it host cell by specific binding
    • -Penetration
    • -Synthesis
    • -Assembly
    • -Release
  17. Adsoption
    • Viral attachment to host cell is mediated by spike protein
    • -spikes recognize only certain host receptors.
  18. Viral penetration/uncoating
    -Naked viruses are endocytosed( requires degradation of cell membrane and capsid prior to uncoating)

    • -Enveloped viruses
    • viral envelop fuses to host cell membrane.

    Allow only capsid to directly enter cytosol
  19. Release of Enveloped viruses
    • -Liberated by bundding or exocytosis
    • allows them to retain a portion of the host cell membrane
  20. Cytophatic Effects
    Damage to the host cell due to a viral infection
  21. Bacteriophage
    Virus that specifically infects bacteria
  22. Viral release
    • -Viral enzymes weaken host cell membrane
    • -leads to rupture the cell (lyses)
    • -Realse numerous virion
  23. Lysogeny
    Insertion of viral DNA into the bacteria host genome.

    Allows viral DNA to be copied with every cell diviision of bacteria
  24. Cultivating Animal viruses
    Eggs provide an intact self-supporting unit for viral maintenance
  25. Normal Vs Infected cells
    • -Normal cells form an enven monolayer of undisturbed cells
    • -forms visible plaques
  26. Noncellular Infectious Agents
    • prions
    • satellite viruseed
    • viroids
  27. Prions
    -protein particle with no nucleic acid, no envelope, no capsid

    • -Diseases
    • Mad cow
  28. Satellite Viruses
    Dependent on other viruses for replication
  29. Viroids
    • -Plant pathogens
    • tomatoes, potatoes, cucumbers
    • -Naked strands of RNA, no capsid
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Chapter 6