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Micro > Ch. 3 Observing Microorganisms through a Microscope > Flashcards

Ch. 3 Observing Microorganisms through a Microscope Flashcards

1
Q

Microorganisms are measured in

A

micrometers and nanometers

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2
Q

Types of light microscopy

A

– Compound light microscopy
– Darkfield microscopy
– Phase-contrast microscopy
– Differential interference contrast (DIC) microscopy
– Fluorescence microscopy
– Confocal microscopy

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3
Q

Compound microscope

A

image from the objective lens is magnified again by the ocular lens

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4
Q

Total magnification =

A

objective lens x ocular lens

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5
Q

Resolution

A

the ability of the lens to distinguish two points

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6
Q

refractive index

A

a measure of the light-bending ability of a medium

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7
Q

Brightfield illumination

A

– Dark objects are visible against a bright background
– Light reflected off the specimen does not enter the
objective lens

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8
Q

Darkfield Microscopy

A
  • Light objects are visible against a dark background
  • Opaque disk placed in condenser
  • Only light reflected off the specimen enters the objective
    lens
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9
Q

Phase-Contrast Microscopy

A
  • Allows examination of living organisms and internal cell
    structures
  • Brings together two sets of light rays, direct rays, and
    diffracted rays to form an image
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10
Q

Differential Interference Contrast Microscopy

A
  • Similar to phase-contrast
  • Uses two light beams and prisms to split light beams,
    giving more contrast and color to the specimen
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11
Q

Fluorescence Microscopy

A
  • Uses UV (short wavelength) light
  • Fluorescent substances absorb UV light and emit longer
    wavelength (visible) light
  • Cells may be stained with fluorescent dyes
    (fluorochromes) if they do not naturally fluoresce
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12
Q

Confocal Microscopy

A
  • Cells are stained with fluorochrome dyes
  • Short-wavelength (blue) light is used to excite a single
    plane of a specimen
  • Each plane in a specimen is illuminated and a three-
    dimensional image is constructed with a computer
  • Can examine layers of cells to a depth of 100 μm
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13
Q

Two-Photon Microscopy

A
  • Cells are stained with fluorochrome dyes
  • Two photons of long-wavelength (red) light are used to
    excite the dyes
  • Can study living cells up to 1 millimeter deep
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14
Q

Super-Resolution Light Microscopy

A
  • Uses two laser beams
    – One wavelength stimulates fluorescent molecules to
    glow
    – Second wavelength cancels out all fluorescence
    except for that in one nm
  • A computer scans the specimen nm by nm, then puts the
    images together
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15
Q

Scanning Acoustic Microscopy

A
  • Measures sound waves that are reflected back from a
    specimen
  • Used to study cells attached to surfaces
  • Resolution of 1 μm
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16
Q

Electron Microscopy

A
  • Uses electrons instead of light
  • The shorter wavelength of electrons gives greater
    resolution
  • Used for images too small to be seen with light
    microscopes, such as viruses
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17
Q

Transmission Electron Microscopy

A
  • A beam of electrons passes through ultrathin sections of
    a specimen, then through an electromagnetic lens, then
    focused on a projector lens
  • Specimens may be stained with heavy-metal salts for
    contrast
  • Magnifies objects 10,000 to 10,000,000x; resolution of 10
    pm
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18
Q

Scanning Electron Microscopy

A
  • An electron gun produces a beam of electrons that scans
    the surface of an entire specimen
  • Secondary electrons emitted from the specimen produce
    a three-dimensional image
  • Magnifies objects 1,000 to 500,000x; resolution of 10 nm
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19
Q

Scanning Tunneling Microscopy

A
  • Uses a tungsten probe to scan a specimen and reveal
    details of its surface
  • Resolution of 1/100 of an atom
20
Q

Atomic Force Microscopy

A
  • Uses a metal-and-diamond probe placed onto a
    specimen; movements are recorded
  • Produces three-dimensional images at near atomic detail
21
Q

Staining

A

coloring microorganisms with a dye that emphasizes certain structures

22
Q

Smear

A

a thin film of a material containing microorganisms spread over a slide

23
Q

Fixed

A

Microorganisms are attached to the slide, which kills the microorganisms

24
Q

Chromophore

A

colored stain consisting of a positive and negative ion

25
Q

basic dye

A

chromophore is a cation

26
Q

acidic dye

A

chromophore is an anion

27
Q

negative staining

A

staining the background instead of the cell

28
Q

Simple stain

A

use of a single dye

29
Q

simple stains highlight the entire microorganism to

A

visualize cell shapes and structures

30
Q

Mordant

A

used to hold the stain or coat the specimen to enlarge it

31
Q

Differential Stains are used to

A

distinguish between bacteria
-Gram stain
-Acid-fast stain

32
Q

Gram-positive bacteria

A

have thick peptidoglycan cell walls

33
Q

Gram-negative bacteria

A

have thin peptidoglycan cell walls and a layer of lipopolysaccharides

34
Q

Acid-Fast Stain

A

binds only to bacteria that have a waxy material in their cell walls, which is not decolorized by acid-alcohol

35
Q

Acid-Fast Stain used for the identification of

A

-Mycobacterium
-Nocardia

36
Q

Special Stains used to distinguish parts of microorganisms

A

-capsule stain
-Endospore stain
-Flagella stain

37
Q

Capsules

A

are a gelatinous covering that do not accept most dyes

38
Q

Suspension of India ink or nigrosin

A

contrasts the background with the capsule, which appears as a halo around the stain

39
Q

Endospores

A

resistant, dormant structures inside some cells that cannot be stained by ordinary methods

40
Q

Primary stain

A

Malachite green, usually with heat

41
Q

Decolorize cells

A

water

42
Q

counterstain

A

safranin

43
Q

spores appear

A

green within red or pink cells

44
Q

Flagella

A

structures of locomotion

45
Q

flagella uses a mordant and carbolfuchsin to

A

thicken appearance of flagella, making them visible under the light microscope

Micro (8 decks)

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