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9 Cards in this Set

  • Front
  • Back
Briefly describe the function of
a compound light microscope
Using a series of lenses and visible light, very small specimens can be examine as well as some of their fine details
light--condenser--thru specimen-obj. lense--ocular lenses.
Define Resolution, total
magnification, refractive index
Resolution: ability of the lenses to distinguish 2 points a specified distance apart. (shorter wavelength of light, greater resolution)

Total Magnification: objective lense times ocular lens (eyepiece)

Refractive Index: the light-bending ability of a medium.
Give advantage of Darkfield &
fluorescence microscopy.

Compare each with brightfield illumination
Darkfield : light objects visible against dark background, uses white light. Specimen can be alive with no stain, unlike Brightfield.

Fluorescence: uses UV light for greater resolution (shorter wavelength). Specimen can be alive.

Brightfield: dark objects on bright background. Specimens usually dead and stained.
How does TEM or SEM differ
from light microscopy?
Both uses beam of electrons instead of light. Use electromagnetic lenses to control light, focus and magnification.

Transmission Electron Microscope: Electrons pass through ultrathin section of specimen. Salts of heavy metals can be used as stain. 2D image.

Scanning Electron Microscope: Electrons reflected from surface of specimen. 3D image
Difference between acidic dye and basic dye
Acidic Dye: Coloring agent is an anion(-). Stains the background. Repelled by slight (-) charge of bacteria.

Basic Dye: coloringagent is cation (+). Stains slightly negative bacterial surface.
Differentiate between positive and negative staining techniques.
Negative staining: preparing coloress bacteria against a colored background.

Positive Staining: Preparing a colored backteria against a colorless background.
Describe Process of making
a bacterial smear.
(1) thin film of material containing microorganism spread over surface of slide.(smear) Let air dry.
(2) Slide is fixed by passing it through flame of Bunsen Burner several times.
(3) Apply stain, wait, then wash off with water and blotted dry.

Fixing prevents the stain washing the microbes off the slide.
Compare simple, differential and
special stains according to purpose, advantages and disadvantages
Simple: use of a single basic dye to see structure of specimen.

Differential: help to identify bacteria by how they react to stains. Ex: Gram Stain to identify Gram Positive or Gram Negative. Gram + usually can be killed by penicillin. Gram - more resistant.Process uses > 1 stain.

Negative Staining: useful to capsules.

Endospore Staining: requires heav to drive stain into endospoes.

Flagella Staining requires a mordant to make flagella wide enough to see.
Give description, staps and stains used for Gram Staining and color difference between Gram + and Gram - specimen
-Primary Stain: Crystal Violet.
+ Purple, - Purple

-Mordant: iodine
+ Purple, - Purple

-Decolorizing Agent:Ethyl Alcohol
+ Purple, - Colorless

-Counterstain: Safranin
+ Purple, - Red