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19 Cards in this Set
- Front
- Back
- 3rd side (hint)
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Parts of a Microscope (Labeled)
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magnification
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In a compound microscope the image from the objective lens is magnified again by the ocular lens.
Total magnification = objective lens ocular lens (10X) objective lens 4X, 10X, 40X, 100X |
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Resolution (resolving power)
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the ability of the lenses to distinguish between two points.
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wavelength
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part of resolution; (visible light)
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numerical aperature
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part of resolution; size of cone of light entering objective.
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Refractive index
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the light-bending ability of a medium; Immersion oil is used to keep light from bending.
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Bright field Illumination
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dark objects are visible against a bright background; light reflected off the specimen does not enter the objective lens.
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Almost all cocci are: + or -
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Gram Positive (blue)
exception: Neisseria gonorrhoeae |
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Fluorescence Microscopy
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Uses Ultraviolet light
Cells may be stained with fluorescent dyes (fluorochromes) Identify unknown organisms in clinical specimens Fluorescent dye linked to specific antibody |
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Electron Microscopy (EM)
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Uses electrons instead of visible light
The shorter wavelength of electrons gives greater resolution; either scanning or transmission |
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Scanning Electron Microscopy (SEM)
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An electron gun produces a beam of electrons that scans the surface of a whole specimen.
Secondary electrons emitted from the specimen produce the image. |
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Transmission Electron Microscopy (TEM)
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whole bacteria and viruses or ultra thin sections of bacteria and viruses
Light passes through specimen, then an electromagnetic lens, to a screen or film. Specimens may be stained with heavy metal salts. |
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Basic Dye (+)
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the chromophore is a cation (+)
Bacteria have a net (-) charge on their surface and are stained by basic dyes. |
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acidic dye (-)
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the chromophore is an anion (-)
Bacteria repel acidic dyes.Only the background is colored Staining the background instead of the cell is called negative staining. |
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Differential staining
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distinguishes between two types of bacteria – uses two different colored basic stains
EX: gram stain |
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Gram stain
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The Gram stain classifies bacteria into gram-positive (blue) and gram-negative (red).
Important because: Gram-positive bacteria tend to be killed by penicillin and detergents. Gram-negative bacteria are more resistant to antibiotics. |
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acid-fast
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Cells that retain a basic stain in the presence of acid-alcohol
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Non–acid-fast cells
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cells that lose the basic stain when rinsed with acid-alcohol, and are usually counterstained (with a different color basic stain) to see them.
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