Microbiology Lecture Exam

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microwiz
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16036
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Microbiology Lecture Exam
Updated:
2010-04-25 22:45:45
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Viruses
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Exam 3
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  1. Viruses are?
    • Non- Cellular
    • Obligate intracellular parasites
    • (have to)(inside)(cell) (kill/harm host cell)
    • They have to get inside a cell to reproduce and then they kill or harm a host cell-usually.
  2. What is the Basic Cell Sturcture?
    • Capsid (protein shell)
    • Genetic Material
    • Double-strand DNA, single strand DNA, D.S RNA, and S.S RNA.
    • Some viruses: also have an envelope; envelope is a piece from previous hoat cell.
    • (phospholipid bilayer with embedded proteins)
  3. What identifies a viruse?
    • -enveloped or not
    • -type of genetic material
    • -size
    • -capsid shape
  4. Types of Viruses? Determined by host cells
    • 1. Bacterial viruses (bacteriophage)
    • -infects bacterial cells--bacteria eater
    • 2. Plant virsues
    • -infects plants
    • 3. Animal viruses
    • -infects animals; including human pathogens
  5. Generalized Life Cycle? (5 steps)
    • 1. Attachment (important step) to host cell
    • viruses only attach to a host cell that only have appropriate receptors on cell surface.
    • (This determines the virus specificity for a host cell) "What host can viruses infect?
    • 2. Penetration/uncoating
    • Virus get into host cell, and capsid is removed (genetic code is avaliable)
    • Host phagocytosis virus
    • -Virus injects nucleic acid
    • -Viral envelope fuse with hos membrane
    • 3. Replication (synthesis of viral parts)
    • Using viral genetic code
    • Use host cells materials (a.a, tRNA, etc) and ribosomes
    • to make:
    • -New viral genetic material
    • -New viral proteins (for capsid or envelope-if appropriate)
    • 4. Assembly
    • Pieces of virus are put together to make new viruses. [virons]
    • Place genetic material in capsid
    • 5. Released from host
    • Host cell lysis (dies)
    • Virus can bud out of cell
  6. Specific viral life cycle?
    • 1. Lytic cycle- see p. 7.6
    • Cause lysis of host cell
    • 2. Lysogenic cycle- see p. 7.7
    • Sometimes host cell lysis; viral DNA become part of host DNA (genome)
    • (1 and 2 happens in bacteria cells0
    • 3. Retrovirus life cycle. see 7.8
    • Happens in animals
  7. How virus help identify a bacteria?
    • (Using viruses that do lytic cycle)
    • A unkown bacteria is inoculated with a phage that kills E. coli, a phage that kills Salmonella, and a phage that kills Proteus.\
    • Bacteria only dies with the phage that kills Salmonella, hence, the bacteria had the correct receptors for the phage to infect.
  8. What is retoviruses?
    • Retroviruses (reverse)
    • Perform the reverse of normal transcription.
    • RNA make DNA by enzyme=reverse transcriptase
    • Ex: H.I.V=Human ImmunoDeficiency Virus (Kills key immune system cells, patient becomes immundeficent)
  9. How to treat viral diseases?
    • Some viral diseases can be trated with anti-viral medications.
    • Many viruses-no safe treatment.
    • Viral replication involves host material and host systems--if blocking viral replication, you can block these host processes.
    • Vaccines- teaching the immune system to attack viruses.
  10. Prions- Proteins
    • Cannot be destroyed ny standard sterization
    • Cause [transmissible spongiform
    • can be transmitted holes in brain
    • encephalopathies]
    • Brain damage
    • Ex. mad cowl disease
    • Prions protein- some a.a sequence as normal brain protiens fold differently.
    • Reproduce-when a prion proteim bumbs into a normal protein, it causes that protein to fold like a prion protein.
    • Transmission- ingestion of infected CNS (brain) tissue.

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