Microscopy, Staining, and Classification Flashcards
Which infectious agents are the smallest? Which are the largest?
prions
full size hemiliths
How do you calculate total magnification?
objective lens magnification multiplied by the ocular lens magnification
What is the definition of resolution?
the ability to distinguish 2 seperate objects as 2 seperate objects. Expressed as the closest distance between two objects
How does total magnification affect the field of view?
reduces the field of view
how does the TM affect the amount of light that reaches the specimen?
higher the magnification the less light reaches the specimen
How do you convert between meters, micrometers, and nanometers?
1 m=1,000,000 micrometers 10^-6
1m= 1,000,000,000 nanometers 10^-9
1 micrometer is 1000 nanometers
What is contrast and how do we improve it?
Contrast is the difference between the subject and the background. Adjustments in the brightness of the light and through staining
what is light refraction
air into water, it slows down, causing it to change direction slightly. This change of direction is called refraction
why do we use immersion oil?
immersion oil has the same refractive index as glass and stops photons from escaping and directs them to the lens
what are two difference between a light and an electron microscope
Differences in total magnification
what microbes can be viewed, light microscope can be alive
light vs electrons used to visualize specimen
describe the use of fluorescent dyes
The dyes that are present and attached to the sample emit a
wavelength of light that is visible against a black background.
immunofluorescence a fluorescent dye is added to antibodies that are specific for a particular antigen
Why must you “fix” a smear to a slide?
prevents the sample from washing away during the staining process
What charge do basic dyes have?
Chromophore is positively charged and enters the cell
what charge do acidic dyes have?
acidic dyes have a negative charge, stains the background of the smear
How does the type of stain (basic or acidic) affect how a specimen is stained?
basic enters cell
acidic stains outside of cells
What is negative staining and what is it good for?
Staining the area around the cells. Good for determining cell sizes
what is a simple stain?
a single stain that stains structures to achieve contrast
what is the function of a mordant in staining procedures? give examples
a mordant holds the stain the structure. Grams iodine or steam
describe how to prepare a smear
Add 1-2 drops of distilled water to a clean slide
gently scoop some specimen with an inoculating loop and add it to the water
let the water air dry
fix the smear for 5-10 seconds over the flame
allow to cool before staining
What cell structural difference are we distinguishing with the gram stain?
the difference in the peptidoglycan layer
Why do gram stain negative lose the purple stain after decolorizing?
the decolorant removes their outer membrane which releases the dye
What is an acid-fast stain, and what are the steps? What bacteria types is it used for?
primary stain carbol fushchin
decolorize
counter stain with methylene blue
mycobacterium and norccardia
which genera (genus) of bacteria are acid fast and what are two diseases they cause?
Used for mycobacterium (TB and leprosy) and Nocardia and organisms with a waxy cell wall
what cell structure is visualized in a capsule stain?
the glycocalyx
