MCB Exam4 B

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Author:
bkheath
ID:
79911
Filename:
MCB Exam4 B
Updated:
2011-04-16 01:58:37
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Controlling microbial growth II
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Controlling microbial growth II
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  1. Cyclic amide functional group which binds to enzymes that cross-link NAM subunits, preventing cross-linkage of NAM subunits, weakening bacterial cell wall & lysing the cell
    Beta-lactam ring
  2. How does inhibition of cell wall synthesis affect bacterial growth?
    Prevents bacteria from increasing amt of peptidoglycan but no effect on existing pep layer (so works only on growing cells)
  3. Example of antibiotic that inhibits synthesis of cell wall
    Penicillin, Vancomycin
  4. Part of antibiotic that is changed when bacteria become resistant
    Beta-lactam ring
  5. Why can taking drugs that inhibit bacterial protein synthesis be harmful to humans too?
    The location of protein synthesis is the ribosome, and the size of ribosomes within the mitochondria of proks and euks differ in size, but according to endosymbiotic theory, human mitochondria originated from bacteria. So both the bacterial AND human ribosomes of the mitochondria will be targeted.
  6. Killing all life forms, including endospores
    Sterilization
  7. Avoiding contamination by technique
    Aseptic
  8. Harsh method of microbial control which is for object use only
    Disinfection
  9. Mild method of microbial control which can be used on skin; bacteria are not killed, just slowed
    Antisepsis
  10. Killing all harmful life forms, not all life forms
    Pasteurization
  11. Form of drug chemicals for all diseases in general, like Rx for heart probs, not only microbial related
    Chemotherapeutics
  12. Suffix -stasis/-static
    stopping growth
  13. Suffix -cide/-cidal
    Killing
  14. Actions of antimicrobial agents (2)
    • Alteration of cell wall and cell membrane
    • Damage proteins and nucleic acids
  15. How damaging cell wall/mem kills microbes (3)
    • Cell wall integrity damaged and can't prevent bursting due to osmotic effects
    • Cytoplasmic membrane cannot control passage of chemicals in/out of cell
    • Damage to viral envelope so can't attach
  16. How damaging proteins/nucleic acids kills microbes
    • Extreme heat or chemicals denature protein by altering 3-D shape, so protein is no longer functional
    • Chemicals, radiation, heat can produce fatal mutants; also affects RNA
  17. Controlling microbes by removing water; microbiostatic
    Desiccation
  18. Effects of high temp on microbe
    • Denaturation of proteins
    • Damage cytoplasmic mem and cell wall
    • Damage structure & function of nucleic acids
  19. Lowest temp that kills all cells in broth in 10 min
    Thermal death point
  20. Time to sterilize volume of liquid at set temp
    Thermal death time
  21. Methods of microbial control using moist heat (4)
    • Boiling
    • Autoclaving
    • Pasteurization
    • Ultrahigh-temp sterilization
  22. Method which kills vegetative cells of bacteria and fungi, protozoan tophozoites, & most viruses w/in 10 min
    Boiling
  23. Method which applies pressure to boiling water which prevents steam from escaping
    Autoclaving
  24. Alternative method which denatures proteins and oxidizes metabolic and structural chemicals, but requires higher temp for longer time than moist heat
    Dry heat
  25. Method of long term preservation of microbial cultures which prevents formation of damaging ice crystals
    Lyophilization
  26. Method of adding salt or sugar to inhibit growth; water in cell is drawn out & cell desiccates; fungi can survive it better than bacteria
    Osmotic pressure
  27. Ionizing vs Non-Ionizing Raditation
    -Denatures DNA; used for meats, fresh fruits & veggies

    -Causes thymimn dimer by UV light; used for disinfecting air, transparent fluids, object surfaces
  28. Effects of chemical methods of microbial control varies with: (7)
    and is more effective against: (2)
    • Temp
    • Length of exposure
    • Amt of organic matter
    • pH
    • Concentration
    • Age of chemical
    • _
    • Enveloped viruses
    • Vegetative cells of bacteria, fungi, protozoa
  29. Major categories of chemical control
    • Phenols
    • Alcohols
    • Halogens-algaecide used in pools: bromide or copper
    • Oxidizing agents
    • Surfactants
    • Heavy metals
    • Gaseous agents
    • Antimicrobics
  30. What enzyme neutralizes hydrogen peroxide?
    Catalase
  31. Why are oxidizing agents a good way to control microbes?
    Oxygen kills proteins; microbial enzymes are oxidized
  32. Examples of oxidizing agents
    Hydrogen peroxide disinfectant & ozone treatment of drinking water (kills cysts)

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