Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Microbiology > Ch. 2 - Microscopy > Flashcards

Ch. 2 - Microscopy Flashcards

You may prefer our related Brainscape-certified flashcards:
Biology 101 flashcards
1
Q

Objective lens

A
  • The lens closest to the specimen

* it forms a magnified image that is further enlarged by one or more additional lenses

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Bright-field microscope

A

• routinely use in microbiology labs to examine both stained and unstained specimens
•Cells are usually killed
• called this because it forms a dark image against a brighter background
• has several objective lenses
• total magnification
-product of the magnification of the ocular lenses and the objective lenses

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Substage condenser

A

• mounted within or beneath the stage and focuses a cone of light on the slide

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Ocular lenses (aka eyepieces)

A

• The curved part of the arm holds the body assembly, to which a nose piece and one or more ocular lenses are attached

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Parfocal

A

• ideally what a microscope should be which is it should remain in focus when objective lenses are changed

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Microscope resolution

A
  • The ability of a lens to separate or distinguish between small objects that are close together
  • wavelength of light used is major factor in resolution
  • shorter wavelength➡️ greater resolution
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Working distance

A

• distance between the front surface of lens and surface of color glass or specimen when it is in sharp focus

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Focal length

A
  • distance between Center of lens and focal point

* short focal length➡️ more magnification

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Immersion oil

A
  • Will replace air that kept many light rays from entering the objective due to reflection and refraction at the surfaces of the objective lens
  • results in an increase in resolution and numerical aperture
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Dark-field microscope

A
  • Image is formed by light reflected or refracted by specimen
  • produces a bright image of the object against a dark background
  • used to observe living unstained preparations
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Dark-field microscope uses

A
  • used to observe internal structures in eukaryotic microorganisms
  • used to identify bacteria such as Treponema pallidum, the causative agent of syphilis
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Phase-contrast microscope

A
  • converts differences in refractive index/cell density into detected variations in light intensity
  • some light rays from hollow cone of light passing through unstained sell slowed/out of phase (dark against bright background)
  • excellent way to observe living cells
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Differential interference contrast microscope (DIC)

A

• creates image by detecting differences in reflective indices and thickness of different parts of specimen
• excellent way to observe living cells
-Live, unstained cells appear brightly colored and 3-D
-cell walls, endospores, granules, vacuoles, and nuclei are clearly visible

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Florescence microscope

A
  • exposes specimen to ultraviolet, violet, or blue light
  • specimens usually stained with fluorochromes
  • shows bright image of object resulting from fluorescent light emitted by the specimen
  • has applications in medical microbiology and microbial ecology studies
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

fluorescent microscopy

A

•Essential tool in microbiology

  • fluorochrome-labeled probes, such as antibodies, or fluorochrome dyes tag specific cell constituents for identification of unknown pathogens
  • localization of specific protein in cells
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Confocal microscopy

A
  • confocal scanning laser microscopy (CLSM) creates sharp, composite 3-D image of specimens by using laser beam, aperture to eliminate Straylight, and computer interface
  • numerous applications including study of biofilms
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Purpose of staining specimens

A
  • increases visibility of specimen
  • accentuates specific morphological features
  • preserves specimen
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Fixation

A

• preserves internal and external structures and fixes them and position
• it inactivates enzymes that might disrupt cell morphology and toughens cell structures so they do not change during staining and observation
• Microorganism usually is killed and attached firmly to slide
• cells are not stained nor distorted during this process
• heat fixation
-routinely used with bacteria and archaea
-preserves overall morphology but not internal structures
• Chemical fixation
-used with larger, more delicate organisms
-protects fine cellular substructure and morphology

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Dyes

A
  • make internal and External structures of cell more visible by increasing contrast with background
  • Basic dyes have positive charges
  • acid dyes have negative charges
20
Q

Simple stains

A
  • A single stain is used

* can determine size, shape, and arrangement of bacteria

21
Q

Differential staining

A
  • divides micro organisms into groups based on their staining properties
  • used to detect presence or absence of structures such as endospores, flagella, and capsules
22
Q

Gram staining

A

• most widely used differential staining procedure
• divides bacteria into two groups based on differences in cell wall structure
1) gram-positive
2) gram-negative

23
Q

Acid fast staining

A

• mostly used for staining members of the genus mycobacterium
- examples: mycobacterium tuberculosis, mycobacterium leprae
• high lipid content in cell walls (mycolic acid) is responsible for their staining characteristics

24
Q

Endospore staining

A
  • heated, double staining technique

* bacterial endospores is one color and vegetative cell is a different color

25
Q

Capsule staining

A
  • used to visualize polysaccharide capsules surrounding bacteria
  • example of negative staining -capsules may be colorless against a stained bacteria
26
Q

Flagella staining

A

• mordant applied to increase thickness of flagella

27
Q

Electron microscopy

A
  • electrons replace light as the illuminating beam
  • wavelength of electron beam is much shorter than light, resulting in much higher resolution
  • allows for study of microbial morphology in great detail
28
Q

Transmission electron microscope (TEM)

A
  • electrons scatter when they pass through thin sections of a specimen
  • transmitted electrons are under vacuum which reduces scatter and are used to produce clear image
  • denser regions in specimen scatter more electrons and appear darker
  • form an image from radiation that has passed through the specimen
29
Q

Electron microscopy specimen preparation

A
  • analogous to procedures used for light microscopy
  • specimens must be cut very thin
  • specimens are chemically fixed and stained with electron dance materials, such as heavy metals, that differentially scatter electrons
30
Q

Negative stain for electron microscopy

A
  • heavy metals do not penetrate the specimen but render dark background
  • used for study of viruses, bacterial gas vacuoles
  • background is stained but not the cells
  • unstained cells appear as bright objects against a dark background
31
Q

Shadowing for electron microscopy

A
  • coating specimen with a thin film of a heavy metal on only one side
  • useful for viral morphology, flagella, DNA
32
Q

Freeze etching for electron microscopy

A
  • freeze specimen then fracture along lines of greatest weakness (I.e., membranes)
  • allows for 3-D observation of shapes of intracellular structures
  • reduces artifacts
  • allows us to observe the shapes of organelles within the cells
33
Q

Scanning electron microscope

A
  • uses electrons excited from the surface of a specimen to create detailed image
  • produces a realistic 3-D image of specimens surface features
  • can determine actually in situ location of microorganisms in ecological niches
  • form image from electrons released from atoms on the object surface
34
Q

Electron cryotomography

A

•Rapid freezing technique provides a way to preserve native state of structures examined in vacuum
• images are recorded from many different directions to create 3-D structures
• provides extremely high resolution images of
-cytoskeletal elements, magnetosomes, inclusion bodies, flagellar motors, viral structures

35
Q

Scanning probe microscopy

A

• among the most powerful microscopes which measure surface features of an object by moving a sharp probe over object surface
• scanning tunneling microscope
-magnification 100 times, can view atoms on surface of a solid
-steady current maintained between microscope probe and specimen
-up down movements of probe as it maintains current is detected, used to create image of surface of specimen
• atomic force microscope
-Sharp probe moves over surface of specimen at constant distance
-up and down movement of probe as it maintains constant distance is detected and used to create image

36
Q

Refractive index

A
  • A measure of how greatly a substance slows the velocity of light
  • The direction and magnitude of bending are determined by the refractive indices of the two media forming the interface
37
Q

Refractive index

A

• The direction and magnitude of bending of light are determined by theses of the two media forming the interface

38
Q

What size object would be the smallest size our eye can successfully detect

A

0.2 mm

39
Q

Heat fixation

A
  • routinely used with bacteria and archaea

- preserves overall morphology but not internal structures

40
Q

Chemical fixation

A
  • used with larger, more delicate organisms

- protects fine cellular substructure and morphology

41
Q

Acid-fast staining steps

A

1) primary staying with basic fuchsin
2) heat to allow basic fuchsin to penetrate cells
3) decolorize with acidic alcohol
4) counterstain with methylene blue

42
Q

Scanning tunneling microscope

A
  • magnification 100 times, can view atoms on surface of a solid
  • steady current maintained between microscope probe and specimen
  • up down movements of probe as it maintains current is detected, used to create image of surface of specimen
43
Q

Atomic force microscope

A
  • The second type of scanning probe microscope to be developed
  • Sharp probe moves over surface of specimen at constant distance
  • up and down movement of probe as it maintains constant distance is detected and used to create image
44
Q

Steps of gram stain process

A

1) primary stain (crystal violet)
2) treatment with iodine solution - increases interaction between Cell and dye so cell is stained better
3) smear is decolorized by washing with alcohol or acetone
4) counterstain usually with safranin - Colors gram-negative bacteria pink to red and leaves gram-positive bacteria dark purple

45
Q

What are two characteristics of many types of dyes used to stain microorganisms

A
  • they are able to bind cells with ionic, covalent, or hydrophobic bonds
  • They have chromatophore groups - contain double bonds that give the dye its color
46
Q

Limitations of light microscope

A
  • Not able to show detailed internal cellular structure

* have a resolution limit of 0.2 micrometers

47
Q

Three types of light microscopes that create images of living specimens

A
  • dark field microscopes
  • phase contrast microscopes
  • differential interference contrast microscopes

Microbiology (5 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions