microbiology

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Author:
mattnjaneal
ID:
222449
Filename:
microbiology
Updated:
2013-06-05 18:11:50
Tags:
viruses
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Description:
chapter 6
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  1. viruses
    • obligate itracellular parasites
    • require a host to replicate
    • lack cellular structure
  2. virion
    complete virus particle in the extracellular state (outside host)
  3. structure of a virus
    • nucleocapsid - genome - dna or rna
    • capsid - protein coat or shell 
    • capsomere - subunit to build capsid
    • envelope - lipid bilayer, host derived when the virus exits
    • spikes (peplomers) - viral proteins, used for attachment to host
    • enzymes - aid infection process
  4. 3 virus enzymes
    • 1. neuraminidase - breaks down glycoproteins and glycolipids; penetrate mucous, spread
    • 2. hemagluttinin - attach to host cell receptors, includes RBC's
    • 3. reverse transcriptase - vRNA which makes a molecule of vDNA
  5. viral capsid shape
    • icosahedral - 20 icosahedral triangles
    • helical capsid - cylindrical, DNA coiled inside
    • complex - includes bacteriophages
  6. viral replication - replication of bacteriophages
    • 1. attachment - host specific
    • 2. penetration - injects nucleic acid
    • 3. biosynthesis - make capsid protein & copies of the genome
    • 4. maturation - assembly, self directed
    • 5. release - lysis of host cell to release new virions
  7. viral replication - replication of animal viruses
    • 1. attachment (adsorption) - host specific; tropism = affinity for (neurotropic virus means affinity for nervous tissue)
    • 2. penetration - 2choices  a) host - phagocytize the virus; receptor mediated endocytosis.  b) fusion of viral envelope with host cell membrane
    • 3. biosynthesis - early proteins, proteins involved with replication; late proteins - capsid protein
    • 4. maturation
    • 5. release - 2 ways, depends on naked vs. enveloped.  naked viruses - released by host cell lysis.  enveloped virus - bud off of the host cell.
  8. viral lytic cycles
    virus released
  9. viral lysogeny
    viral DNA lays dormant in a host cell.  Latent or dormant in CNS.  ex: VZV - varicella zoster virus.
  10. classification of virus
    • by family (ex: veridae)
    • by genus (ex: herpes)
    • by species (ex: 1 or 2)
    • ex: HSV1
  11. 3 forms of virus cultivation
    • living animals - infect mice, rabbits, guinea pigs, etc
    • embryonic eggs - grow virus in fertilized chicken eggs; may infect chick or membrane
    • tissue cultures - homogenize and separate cells in a tissue
  12. viral tissue histology
    viral infection can cause changes in host cell.  CPE's - cytopathic effects.  ex: rabies virus - leaves negri bodies in cytoplasm
  13. immunoassays
    • titer - determine amount of virus in sample
    • elisa test kit - color change when substrate is added to a positive test.  ELISA = Enzume linked immunosorbent assay
    • lates bead agglutination - anti vrus clumpls together
  14. plague formation
    plague - zone of host cell lysis; holes formed by virus
  15. host defenses against virus
    • phagocytes - engulf and destroy viruses
    • T lymphocytes - CD8+ cells, killer T cells, recognize and destroy viral infected host cells
    • Interferon - chemical released by viral infected cells, signals neighboring cells to produce anti viral protein; recruits natural killer cells
  16. antiviral medications
    • base analogs - mimic nucleotides, so when a virus inserts a base analog replication stops
    • reverse transcriptase inhibitors - treating retroviral infections
    • protease inhibitors - viral mRNA- protease, cut the polypeptide
    • neuraminidase inhibitors - disrupt the release of virus (progeny)
  17. viral vaccines - immunization
    • inactivated (killed) - treat the virus with formaldehide to inactivate
    • attenuated - weakened strain, infected without symptoms
    • viral subunits - proteins from surface
    • DNA vaccines - shoot the beads into muscle, muscle cells express the viral DNA
  18. chemical inactivation of a virus
    • formaldehyde - denatures protein
    • lipid solvents - detergents - effective against enveloped viruses
  19. physical inactivation of a virus
    • heat - denatures protein
    • UV radiation - disrupt nucleic acid
    • X rays - disrupt nucleic acids
  20. subviral particles -
    • smaller than viruses but cause infection; no capsid or genome
    • viroid - plant pathogens, consist of small RNA genome, insects transmit between plants
    • prion - proteinaceous infectious particle. 
  21. prion disease
    • spongiform encephalopathy
    • degeneration of brain tissue
    • PrPc - normal protein in brain tissue
    • PrPsc - improper folding, builds up in tissues, affects structure of brain tissue
    • Kuru - cannibalistic tribe
    • BSE - bovine spongiform encephalopathy- mad cow disease
    • scrapie - sheep
  22. transformation
    • healthy cells become cancerous
    • proto-oncogenes; genes that regulate cell growth and differentiation; vDNA take over control of gene.  ex: HPV triggers cervical cancer

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