Study Guide Quiz 1 for Lab

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Study Guide Quiz 1 for Lab
2013-09-16 00:33:21
Biology 106 Quiz Lab

Study Guide
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  1. Brightfield

    What is the advantage of using this type?
    can view both living and stained samples
  2. Darkfield

    What is the advantage of using this type?
    more clearly delineates living, unstained material
  3. Phase-contrast

    What is the advantage of using this type?
    enhances contrast; excellent for living, unstained material and internal structures
  4. Fluorescence

    What is the advantage of using this type?
    fluorescent dyes allow staining of specific large molecules or structures
  5. Electron

    What is the advantage of using this type?
    for greater magnification and resolution
  6. Explain why you use oil with the 1000x objective.
    Because oil produces greater resolution.
  7. Parfocal
    when one objective lens is in focus all objective lenses are near focus
  8. Resolution
    ability of the lenses to distinguish two points as being separate
  9. Heat fixation
    heated to attach microbes to slide and kill the microbes
  10. Explain how you would fix the following microscope problems when using 1000x oil immersion lens:

    a. Insufficient light to view specimen (light level was good at 400x):
    Gradually open the irisĀ  diaphragm and adjust it.
  11. Explain how you would fix the following microscope problems when using 1000x oil immersion lens:

    b. when you move from 400x to 1000x specimen is no longer in the field:
    Object wasn't in the center of the field, may be out of focus and undetectable, and I didn't add oil.
  12. Explain how you would fix the following microscope problems when using 1000x oil immersion lens:

    c. What criteria can you use to distinguish artifact from bacteria?
    I can use heat fixing to distinguish artifact from bacteria.
  13. Explain and be able to calculate the total magnification on a given microscope objective:
    Total magnification is the product of the magnification of the object and it is equal to objective lens times ocular lens. For example, if objective lens is 4x and ocular lens is 10x, then we get (4x)(10x)= 40 for total magnification.
  14. sub-culturing
    transferring microbes from one medium to another
  15. source culture
    the culture microbes are obtained from
  16. What criteria do you use to know that your loop/needle is sterile?
    I flame inoculating loop or needle until red/glowing entire length, never lay down after heating, cool 10-20 seconds and can cool further by touching inside tube or plate.
  17. Why do you flame the opening of the test tube and keep the opening at an angle when lids are removed during sub-culturing?
    Because we have to heat the air to form current that prevents contamination and to prevent contaminants in the air from falling in.
  18. one reason to choose "slant"
    easy to store
  19. one reason to choose "plate"
    able to isolate colonies
  20. one reason to choose "broth"
    bacteria form natural arrangements
  21. one reason to choose "deep"
    can grow bacteria to test motility and oxygen requirements
  22. pure culture
    contain only one type of organism; in any type of media
  23. colony
    genetically identical group of organisms; arise from a single cell
  24. Explain why you never "cross your tracks" or re-enter sector 1 when streaking a plate isolate colonies.
    Because more microbes are likey to be picked up if I cross tracks and make dilution process more difficult.
  25. acidic stains
    are used to stain the slide bacteria are one (India ink)
  26. Basic stains
    are used stain bacterial cells (methylene blue)
  27. Why must the smear on the slide be completely dry before heat fixation?
    Because it avoids thick, dense smears, allows to air dry completely.
  28. What are the two reasons bacterial smears are heat fixed?
    • 1. It keeps microbes on slides (smear washes away if not "fixed" on slide)
    • 2. It kills microbes
  29. one reason to use "simple stains"
    easy to reason
  30. one reason to use "differential stains"
    distinguish between different bacteria
  31. When you do the capsule stain why must you counterstain crystal violet?
    To contrast color to primary stain, make sure stain cells are inside capsules, and confirm bacteria are present.
  32. primary stain
    crystal violet, stains peptidoglycan in all cells purple
  33. mordant
    gram's iodine, increases cell's affinity for primary stain
  34. decolorizing agent
    95% ethyl alcohol, removes crystal violet
  35. counterstain
    safranin, stains decolorized gram (-) cells red so they can be observed
  36. four reasons of a gram positive organism might appear red after gram staining
    • 1. old bacterial culture (>24-48 hours) or damaged during heat fixation
    • 2. common in bacillus sp culture (especially older one)
    • 3. over-decolorization: primary stain (crystal violet) removed
    • 4. primary stain not left on long enough
  37. Why do you heat the primary stain in an endospore stain?
    Because heat is applied in order to damaged spore coat so it will take up stain
  38. Under what conditions do roganism form spores
    organisms form spores in green
  39. two genera of bacteria that form spores
    • clostridium
    • bacillus