Microbiology Exam 1; Chapter 3
What do we need a microscope for?
To see microorganisms
How many lenses does a simple microscope have?
What is light microscopy?
Microscopes that use visible light to observe specimen
What are the types of light microscopy?
Compound, Darkfield, Phase-contrast, Fluorescence
What two things magnify an image on a compound microscope?
Objective lens and a ocular lens
How do you solve for total magnification?
Objective lens x ocular lens
What is resolution?
The ability of the lenses to distinguish two points
What is a refractive index?
measure of the light-bending ability of a medium
How does brightfield illumination work?
Dark objects visible against a bright background
What is darkfield illumination?
Light objects visible against a dark background
What is phase-contrast microscopy? What does it allow you to see?
Diffraction of light that passes through a specimen; internal structures
What is differential interference contrast microscopy?
Same as phase-contrast but with two beams of light
What kind of light does fluorescence microscopy use?
How does a fluorescent microscope work with fluorescent substances?
Fluorescent substances absorb the UV light
In confocal microscopy, what are the cells stained with?
What kind of wavelengths and what color light is used in confocal microscopy
Short wavelengths and blue light
What dimension does a confocal microscope produce?
In electron microscopy, shorter wavelengths of electrons gives greater what?
What can specimen be stained in with electron microscopy?
Heavy metal salts
According to Atul Gawande, what's the most preferred method of hand washing?
What does staining a specimen do?
Colors the microbe and emphasizes structures
What is a smear?
Thin film of microbes on a slide
What does it mean to 'fix' a smear?
Heat it as to kill the bacteria
The chromophore in a basic dye is a(n)?
The chromophore in an acidic dye is a(n)?
What is the definition of staining the background instead of the cell?
What is a simple stain?
Single basic dye
What does a mordant do?
Holds/coats the specimen to enlarge it
What are differential stains used for?
Distinguish between bacteria
Gram stain classifies bacteria into what two groups?
Gram-positive and gram-negative
Gram-negative bacteria are resistant to what?
Gram-positive bacteria tend to be killed by what?
Penicillin and detergents
What is an acid-fast stain?
Used to identify mycobacterium
Negative staining is useful for?
Heat is required to drive a stain into?
Why does flagella staining require a mordant?
To make the flagella wide enough to see