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53 Cards in this Set
- Front
- Back
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4 types of Light Microscopes |
Bright-field microscope Dark-field microscope Phase-contrast microscope Fluorescence microscope |
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Refractive Index |
a measure of how greatly a substance slows the velocity of light |
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Focal point |
specific place where light rays focus |
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Focal lenght |
distance between center of lens and focal point |
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Relationship between magnification and focal length |
The greater the magnification, the shorter the focal length (inversely proportional) |
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The Bright-Field microscope |
-produces a dark image against a brighter background (specimen is dark, field is white) |
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Total magnification |
product of the magnifications of the ocular lens and the objective lens |
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Parcentral microscopes |
Center of field stays the same as magnification changes |
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Parfocal microscopes |
Remain in focus when objectives are changed |
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Relationship between resolution and wavelength |
The greater the resolution, the shorter the wavelength (inversely proportional) |
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Resolution |
Ability of a lens to separate or distinguish small objects that are close together |
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Resulting Power = |
wavelength of light in nm _____________________________________ 2 X Numerical aperture of lens |
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Working distance |
Distance between the front surface of lens and surface of cover glass or specimen |
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Relationship between magnification and working distance |
As magnification increases, working distance decreases (inversely proportional) |
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Relationship between magnification and field of view |
As magnification increases, field of view decreases (inversely proportional) |
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Purpose of immersion oil |
Helps to provide more light |
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Relationship between magnification and amount of light passing through specimen |
As magnification increases, the amount of light passing through specimen decreases (inversely proportional) |
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The Dark-Field Microscope |
produces a bright image of the object against a dark background (used to observe living, unstained preparations) |
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The Phase-Contrast Microscope |
Enhances the contrast between intracellular structures having slight differences in refractive index |
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The Fluorescence Microscope |
Exposes specimen to ultraviolet, violet, or blue light Specimens stained with fluorochromes Shows a bright image of the object resulting from the fluorescent light emitted by the specimen |
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Wavelength of visible light |
400-700nm |
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Electromagnetic Spectrum |
Radio Microwave Infrared Visible Light Ultraviolet X-Ray Gamma (Rich Men In Vegas Use eXpensive Gadgets) |
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Immunofluorescence |
utilizes fluorescent-labeled antibodies to detect specific target antigens |
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antigens |
substance that causes your immune system to produce antibodies against it |
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antibodies |
large, Y-shaped proteins which function to identify and help remove foreign antigens or targets such as viruses or bacteria |
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The Differential Interference Contrast Microscope |
Creates image by detecting differences in refractive indices and thickness of different parts of specimen -aka Normaski microscope |
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Purpose of the Preparation and Staining of Specimens |
-Increases visibility of specimen -Accentuates specific morphological features -preserves specimens |
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Fixation |
-Process by which internal and external structures are preserved and fixed in position -Process by which organism is killed and firmly attached to the microscope slide |
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Heat fixing |
Preserves overall morphology but not internal structures |
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Chemical fixing |
protects fine cellular substructure and morphology of larger, more delicate organisms |
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Purpose of dyes |
make internal and external structures of cell more visbile by increasing contrast with background |
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Chromophore |
chemical groups give dye its color |
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Dyes are able to ______ |
bind cells by ionic, covalent, or hydrophobic bonding
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Basic Dyes |
Positively charged |
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Acid Dyes |
Negatively charged (ex. Nigrosin) |
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Simple staining |
a single staining agent is used |
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Positive staining |
dyes bind to cell surface (Basic) |
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Negative staining |
dyes do not bind to cell surface, but binds to the surface of the slide (Acid) |
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Differential staining |
Divides microorganisms into groups based on their staining properties |
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Gram staining |
-most widely used differential staining procedure -divides bacteria into two groups based on differences in cell wall structure |
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Name of each objective |
4X Scanning 10X Low Power 40X High Power 100X Oil Immersion Lens |
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Steps in Gram Staining |
1. Primary Stain: Crystal Violet 2. Mordant: Gram's Iodine 3. Ethanol 4. Secondary Stain: Safranin |
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Acid-fast Staining |
-useful for staining Mycobacterium due to high lipid content in cell walls |
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Negative Staining |
Widely used to visualize diffuse capsules surrounding the bacteria; those capsules are unstained by the procedure and appear colorless against a stained background |
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Spore staining |
Double staining technique by which bacterial endospores are left one color and the vegetative cell are a different color |
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Endospore |
non-reproductive structure to ensure survival |
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Flagella staining |
Mordants are applied to increase the thickness of flagella to make them easier to see after staining |
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Electron Microscopy |
Beams of electrons are used to produce images -wavelength of electron beam is shorter than light, therefore higher resolution |
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Shadowing |
coating specimen with a thin film of heavy metal -makes specimen appear 3D and darker |
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Freeze-etching |
freeze specimen then fracture along lines of greatest weakness (membranes) |
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Transmission Electron MIcroscope |
-electrons scatter when they pass through thin sections of a specimen, transmitted electrons (those that don't scatter) are used to produce the image |
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Scanning Electron Microscope |
-uses electrons reflected from surface of specimen to create image -produces a 3D image of specimen's surface features |
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Newer techniques in microscopy |
Confocal microscopy and scanning probe microscopy |
