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What are the 3 types of microscopes?
- Light
- Electron
- Atomic Force
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What is a light microscope?
- Visible light passes through a series of lenses to produce an image.
- Usually magnifies 1000x
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What is an electron microscope?
- Microscope that uses electron beams to produce a magnified image.
- Can magnify up to 100,000x
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What is an Atomic Force Microscope?
A microscope that uses a probe to move in response to the force between the microscope and specimen to project a map of the bumps and valleys of the specimen.
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What is magnification?
Enlarging the size of something as an optical image.
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What is resolution?
The ability to measure the angular separation of images that are close together; ie, how "clear" an image is.
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What is contrast?
Reflects the number of visible shades in a specimen, with "high contrast" being black and white.
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What is resolving power?
- Determines how much detail can be seen.
- Minimum distance between two objects that still appear as separate objects.
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What does resolution depend on?
Quality of the lenses and wavelength of illuminating light.
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What is the maximum resolving power of most light microscopes?
1 x 10-6
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What is immersion oil?
An oil that reduces light refraction, and has nearly the same refractive as glass.
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How is higher contrast achieved in microscopy?
Specimen staining.
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What is a scanning electron microscope used for?
Observing surface details of cells.
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What is a fluorescent microscope?
Used to observe organisms that are naturally fluorescent, or stained with fluorescent dyes?
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What are stains made of?
Organic salts
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How do dyes work?
Carry (+) or (-) charge and bind to certain cell structures in a molecule.
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How do basic dyes work?
- Carry a positive charge and bond to structures with a negative charge.
- Commonly stain the cell
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How do acidic dyes work?
- Carry a negative charge and bond to structures with a positive charge.
- Commonly stain the background.
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What are the common basic dyes used?
- Crystal violet
- Safrinin
- Methylene Blue
- Malachite Green
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What is a simple stain?
Uses one basic stain to increase contrast between specimen and background with no differentiation between cell types.
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What is a differential stain?
A stain using a series of reactants to distinguish one bacteria from the other.
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What are the two most common types of differential stains?
- Gram stain
- Acid-fast stain
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What is a gram stain?
- Most widely used procedure for staining bacteria
- Developed by Dr. Hans Christian Gram
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What color are gram stains?
Gram positive - stains purple
Gram negative - stains red or pink
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What are the steps in a gram stain?
- Fixation
- Primary Stain - Crystal Violet, Dyes positive and negative cells
- Iodine Treatment - Holds primary dye onto cell
- Decolorizer - removes stain from gram negative cell
- Counter Stain - Safrinin, restains gram negative cell
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What is an acid-fast stain?
Stain used to stain organisms that resist convention staining, like Mycobacterium.
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What are the steps in acid-fast staining?
- Primary Dye
- Decolorizer
- Counter Stain
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What makes some bacteria difficult to stain conventionally?
High lipid concentration in cell wall prevents uptake of dye.
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What does a capsule stain do?
- Stains background
- Allows capsule to stand out around organism
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What is an endospore stain?
Uses heat to enhance endospore
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What is a flagella stain?
Staining that inscreases the diameter of the flagella, making it more visible.
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