Micro test 3 - Ch. 12

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  1. how many infectious diseases are caused by viruses?
    more than 80%
  2. viruses are defined as
    obligate intracellular parasites - they live outside a cellular host
  3. viruses have what goal?
    productive infection
  4. viruses can infect:
    • bacteria (bacteriophages)
    • plant cells
    • animal cells (humans included in this group
  5. intact viral particle is called:
  6. capsid
    protein coat surrounding viral nucleic acid
  7. capsid made up of:
  8. 2 types of viruses:
    • DNA viruses
    • RNA viruses
  9. virion structure must overcome 2 basic problems:
    • must be strong enough to protect viral nucleic acid
    • must be able to release viral nucleic acid for infection
  10. nucleocapsid
    nucleic acid plus capsid
  11. envelope
    phospholipid bilayer with embedded glycoproteins surrounding capsid in enveloped virus
  12. virion
    complete infectious viral structure: nucleic acid plus capsid for non-enveloped virus; nucleic acid plus capsid plus envelope for enveloped virus
  13. how do capsomeres give capsid structural symmetry?
    bond together
  14. viruses possess what types of symmetry?
    • helical
    • icosahedral
  15. 2 shapes of helical viruses:
    • rod - straight and relatively rigid
    • filamentous - flexible, curved, or coiled
  16. Classification of viruses
    • type of genetic material
    • capsid shape
    • number of capsomeres
    • size of capsid
    • presence/absence of envelope
    • type of host it infects
    • type of disease it produces
    • target cell
    • immunologic and antigenic properties
  17. icosahedral viruses' shape derived from?
    20 triangular faces that make up capsid - capsid insert has 12 points of symmetry
  18. 2 types icosahedral viruses
    • simple
    • complex
  19. viral envelopes
    form when viral glycoproteins and oligosaccharides associate with plasma membrane of host cell
  20. all envelopes have:
    phospholipid bilayer
  21. envelopes vary in:
    • size
    • morphology
    • complexity
    • composition
  22. envelope glycoproteins
    firmly embedded in the envelope bilayer, facilitated by domains of host membrane proteins called "spanners"
  23. envelope glycoproteins form:
    spikes or other structures on the outside of the virion that can be used to attach to host cell
  24. viral genomes packaged in one of three ways:
    • directly in the capsid
    • enclosed in special proteins
    • enclosed in proteins from host cell
  25. infection cycle first worked out in
  26. animal virus infections can be either:
    • lytic
    • lysogenic
  27. bacteriophages go through 5 steps in replication process, ending in lysis of the cell:
    • attachment
    • penetration
    • uncoating
    • biosynthesis
    • maturation
    • release
  28. what happens in a lytic infection?
    host cells fill with virions and burst
  29. lysogenic infections also known as:
    latent infections
  30. what happens in lysogenic infections?
    viral genome becomes incorporated into the host cell's DNA, remaining this way for an extended period - host cell lives
  31. attachment and penetration of a lytic infection involve:
  32. virion attachment occurs when?
    when virion binds to specific receptors on a host cell
  33. some viruses require what to attach?
    co-receptor - without it, no infection
  34. viral-host cell interactions occur through:
    random collisions
  35. lytic infections produce:
    maximum number of virions
  36. host cell must be what for infection to succeed?
    permissive - must contain all components required to make new virions
  37. viral infections at apical cell surface usually cause what kind of infection?
    acute infection
  38. viral infection at basolateral cell surface becomes?
  39. lipid rafts
    • specific areas on the host cell membrane to which many viruses attach
    • rich in cholesterol, fatty acids, and other lipids
    • more reliable for stable attachment
    • site of release for many viruses
  40. virus-receptor binding is:
    high affinity - conformational interactions
  41. receptors can determine
    host range of virus
  42. receptors used:
    • some viruses use more than one type
    • some receptors shared by many viruses
  43. non-enveloped virus binding
    takes place between viral capsid and receptor
  44. enveloped virus binding
    takes place between viral envelope proteins and receptor
  45. penetration
    once attached, virus must gain entry to the host cell
  46. uncoating occurs in 3 places
    • at plasma membrane
    • in cytoplasm
    • at nuclear membrane
  47. non-enveloped virus enclosed in:
    vesicle - early endosome (fuse with or become late endosomes)
  48. late endosomes fuse with:
    lysosome where uncoating begins
  49. enveloped viruses - envelope fuses with
    host cell membrane - fusion mediated by specialized fusion proteins of host cell, resulting in formation of fusion pore (large opening allowing viral entry)
  50. viral infection requires:
  51. newly synthesized viral components moved to other locations for:
    assembly of viral particles
  52. viral components moved in:
    vesicles using host cell microtubules (specialized host cell proteins sometimes used)
  53. DNA viruses use what to cross nuclear membrane
    host cell import pathways - pathways form pores in nuclear membrane
  54. RNA viruses use what to convert RNA to DNA?
    reverse transcriptase
  55. newly converted viral DNA put into:
    pre-integration complex - this moves into host cell nucleus during mitosis when nuclear membrane broken down
  56. biosynthesis - double-stranded DNA viruses
    • one strand of viral DNA transcribed into mRNA
    • uses either host cell or viral RNA polymerase
  57. biosynthesis - single-stranded DNA
    • viral strand used as a template to make complementary strand of DNA
    • uses host cell's DNA polymerase
  58. complementary copy (in single-stranded DNA biosynthesis)
    • transcribed into mRNA
    • used to make new copies of viral genome
  59. replication of DNA virus genomes requires:
    • synthesis of at least one viral protein
    • expression of several viral genes
  60. replication of DNA virus genomes is performed by:
    host cell machinery
  61. latent DNA viruses require:
    much less DNA replication
  62. virus does what to host DNA synthesis?
    • inhibits
    • all polymerases and proteins concentrate on viral DNA synthesis
  63. replication compartments
    • specialized sites formed in host cell
    • essentially viral factories
  64. replication compartments contain:
    both DNA templates and host cell replication machinery
  65. compartmentalization allows:
    exponential viral replication
  66. in latent DNA viruses, viral genome inserted where?
    into host chromosome
  67. how many viral genes expressed in latent viral replication?
    • small number
    • limited number of viral genomes replicated
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Micro test 3 - Ch. 12
2011-10-18 15:08:46

Micro test 3 - Ch. 12
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