the micro basics

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the micro basics
2010-12-09 21:44:06
first exam

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  1. micrometer
    • (micron)
    • 1 millionthof a meter, "um"
  2. nanometers
    1 billionth of a meter, designated as nm
  3. Basic system in micro-biology
    • light microscope aka compound microscope
    • it uses two lenses
    • objective lens: nearer the object ocular
    • lens: nearer the eye
  4. mechanics of light microscopy
    • light passes into substage condenser
    • condenser focuses light into a sharp cone
    • light passes through stage into slide and bounces off object
    • objective lens captures light forming a “real image”this image travels to ocular lens, magnifying it again to form the virtual image
  5. low power
  6. high power
  7. oil immersion
  8. Resolving Power
    • (RP) Lens system must transmit light without variation and allow closely spaced objects to be clearly distinguished
    • RP determines the size of the smallest object that can be seen clearly with a given lens
    • RP = wavelength of white light / 2NA wave length of white light is 550nm
    • NA = numerical aperture of lense
  9. Working Distance
    • amount of clearance between slide and bottom of objective
    • larger power of objective lens means less working distance
  10. Oil immersion lens
    • light (because of low refractive index) bends abruptly when leaving glass side and entering air
    • low and high power objectives wide enough to still capture light
  11. Simple Stain
    • since cytoplasm has a negative charge, and basic dyes have apositive charge
    • dye attracted to cytoplasm of cell
  12. Negative Stain
    stains the background, and not the actual organism
  13. Gram Stain
    • a very valuable way to subdivide organisms
    • this is used as a preliminary step to identifying unknown organisms
    • differentiates bacteria into two group so
    • Gram positive stains: blue (ends purple)
    • Gram negative – stain red (ends pink)
  14. Dark-field microscopy
    background remains dark while object illuminated
  15. Phase-Contrast Microscopy
    • light beams split so rays are slightly out of phase
    • separated beams of light pass through and around object
    • small differences in densities show up as variation of brightness and contrast
    • advantage: can view living organisms without staining
  16. Fluorescence Microscopy
    organisms coated with fluorescent dye (i.e.:fluorescein) and illuminated with UV light
  17. Transmission Electron Microscope
    • Used to photograph detailed structures within cells
    • Need ultra thin sections of material so electrons can penetrate
  18. Scanning Electron Microscopy
    Used to see surfaces of objects in natural state without sectioning