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MICRO > light microscopy > Flashcards

light microscopy Flashcards

0
Q

different types of light microscopy (4)

A

bright-field
phase-contrast
dark-field
fluorescence

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1
Q

compound light microscope

A

uses visible light to illuminate cells

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2
Q

bright-field microscope

A

specimens are visualized b/c of differences in contrast (density) b/w the specimen and surroundings

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3
Q

bright field microscope has 2 lenses to form the image:

A

objective lens

ocular lens

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4
Q

calculating magnification of bright field microscope

A

objective mag X ocular magnification

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5
Q

max magnification of bright field microscope:

A

about 2,000 times

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6
Q

what are the 6 parts of a bright field microscope

A
  • ocular lens
  • objective lens
  • condenser
  • stage
  • focusing knobs
  • light source
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7
Q

2 principles of light microscopy

A

magnification

resolution

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8
Q

magnification

A

ability to make an object larger

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9
Q

resolution

A

ability to distinguish 2 adjacent objects as separate and distinct

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10
Q

what is resolution determined by?

A

wavelength of light used
and
numerical aperture of lens used

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11
Q

limit of resolution for a light microscope

A

about .2 micrometers

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12
Q

how does improving contrast help microscopy?

A

results in a better final image

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13
Q

staining improves

A

contrast

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14
Q

dyes

A

organic compounds that bind to specific cellular materials

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15
Q

examples of stains used (3):

A

methylene blue
safranin
crystal violet

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16
Q

differential stains aka

A

the gram stain

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17
Q

what do differential stains do?

A

separate bacteria into groups

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18
Q

bacteria can be divided in 2 groups:

A

gram-positive

gram-negative

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19
Q

gram-positive

A

appear purple

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20
Q

gram negative

A

appear red after staining

21
Q

phase-contrast microscopy improves

A

the contrast of a sample without use of a stain

22
Q

when was phase contrast invented and by who?

A

1936, frits zemike

23
Q

how does the phase contrast microscopy allow improvement of contrast?

A

the phase ring amplifies differences in the refractive index of the cell and surroundings

24
Q

what is phase-contrast allowed for use for visualization of

A

live samples

25
Q

what is the resulting image of a phase contrast microscopy?

A

dark cells on a light background

26
Q

dark-field microscopy

A
  • when light reaches the specimen from the sides

- the light reaching the lens has been scattered by specimen

27
Q

how does the image appear on a dark-field microscopy and what is this good for observing in cells?

A

image appears light on a dark background

excellent for observing motility

28
Q

what is the average size of a cell width?

A

about 8-10 microns in width

29
Q

fluorescence microscopy is used for

A

visualizing specimens that fluoresce

30
Q

how do fluorescence microscopy allow one to see fluorescent specimens?

A

it emits light of one color when illuminated with another light

31
Q

autofluorescence

A

cells that fluoresce naturally

32
Q

how can a cell fluoresce if it is not autofluorescence?

A

they have been stained with a fluorescent dye (ex. DAP)

33
Q

what is fluorescent microscopy used for in microbiology?

A

used in microbial ecology for enumerating bacteria in natural samples

34
Q

Differential Interference Contrast (DIC) microscope uses what to create 2 distinct different beams of polarized light

A

polarizer

35
Q

DIC microscopy gives what 3 structures a 3d appearance?

A

endospores, vacuoles, and granules

36
Q

what microscope can come sometimes see structures that bright field cannot?

A

DIC

37
Q

confocal scanning laser microscopy (CSLM) uses what?

A

a computerized microscope occupied with a laser source to generate a 3d appearance

38
Q

what microscope can focus the laser on a single layer of the specimen?

A

confocal scanning laser microscope

39
Q

what is the resolution of a confocal scanning laser microscope?

A

0.1 micrometers resolution

40
Q

microscopes that use electrons instead of photons to image cells and structures

A

electron microscope

41
Q

name 2 types of electron microscopes

A

transmission electron microscope
scanning electron microscope

TEM and SEM

42
Q

hoe does the electron microscope work?
it uses what to function as lenses?
the system operates as a what?

A

electromagnets

vacuum

43
Q

is the magnification of transmission electron microscope high?

what is the resolution?

A

yes its high magnification

resolution= 0.2 nanometers

44
Q

what are the stipulations for a specimen to be observed with transmission electron microscope? (2)

A

sliced thin and must be stained

45
Q

what level of visualization does the transmission electron microscope allow?

A

the molecular level

46
Q

what is the stipulation for a scanning electron microscope? SEM
1

A

specimen is coated with a thin layer of heavy metal

47
Q

what type of microscope scans the object with an electron beam?

A

scanning electron microscopy

48
Q

How does the SEM work?

A

the electrons are scattered throughout the metal, and a detector collects them and the image is produced

49
Q

what type of microscope can scan large specimens?

what is the magnification range?

A

SEM

range of magnification: 15-100,000 times

MICRO (3 decks)

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