light microscopy

Question 0

different types of light microscopy (4)

Answer 0

bright-field
phase-contrast
dark-field
fluorescence

Question 1

compound light microscope

Answer 1

uses visible light to illuminate cells

Question 2

bright-field microscope

Answer 2

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

Question 3

bright field microscope has 2 lenses to form the image:

Answer 3

objective lens

ocular lens

Question 4

calculating magnification of bright field microscope

Answer 4

objective mag X ocular magnification

Question 5

max magnification of bright field microscope:

Answer 5

about 2,000 times

Question 6

what are the 6 parts of a bright field microscope

Answer 6

• ocular lens
• objective lens
• condenser
• stage
• focusing knobs
• light source

Question 7

2 principles of light microscopy

Answer 7

magnification

resolution

Question 8

magnification

Answer 8

ability to make an object larger

Question 9

resolution

Answer 9

ability to distinguish 2 adjacent objects as separate and distinct

Question 10

what is resolution determined by?

Answer 10

wavelength of light used
and
numerical aperture of lens used

Question 11

limit of resolution for a light microscope

Answer 11

about .2 micrometers

Question 12

how does improving contrast help microscopy?

Answer 12

results in a better final image

Question 13

staining improves

Answer 13

contrast

Question 14

dyes

Answer 14

organic compounds that bind to specific cellular materials

Question 15

examples of stains used (3):

Answer 15

methylene blue
safranin
crystal violet

Question 16

differential stains aka

Answer 16

the gram stain

Question 17

what do differential stains do?

Answer 17

separate bacteria into groups

Question 18

bacteria can be divided in 2 groups:

Answer 18

gram-positive

gram-negative

Question 19

gram-positive

Answer 19

appear purple

Question 20

gram negative

Answer 20

appear red after staining

Question 21

phase-contrast microscopy improves

Answer 21

the contrast of a sample without use of a stain

Question 22

when was phase contrast invented and by who?

Answer 22

1936, frits zemike

Question 23

how does the phase contrast microscopy allow improvement of contrast?

Answer 23

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

Question 24

what is phase-contrast allowed for use for visualization of

Answer 24

live samples

Question 25

what is the resulting image of a phase contrast microscopy?

Answer 25

dark cells on a light background

Question 26

dark-field microscopy

Answer 26

- when light reaches the specimen from the sides | - the light reaching the lens has been scattered by specimen

Question 27

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

Answer 27

image appears light on a dark background excellent for observing motility

Question 28

what is the average size of a cell width?

Answer 28

about 8-10 microns in width

Question 29

fluorescence microscopy is used for

Answer 29

visualizing specimens that fluoresce

Question 30

how do fluorescence microscopy allow one to see fluorescent specimens?

Answer 30

it emits light of one color when illuminated with another light

Question 31

autofluorescence

Answer 31

cells that fluoresce naturally

Question 32

how can a cell fluoresce if it is not autofluorescence?

Answer 32

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

Question 33

what is fluorescent microscopy used for in microbiology?

Answer 33

used in microbial ecology for enumerating bacteria in natural samples

Question 34

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

Answer 34

polarizer

Question 35

DIC microscopy gives what 3 structures a 3d appearance?

Answer 35

endospores, vacuoles, and granules

Question 36

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

Answer 36

DIC

Question 37

confocal scanning laser microscopy (CSLM) uses what?

Answer 37

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

Question 38

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

Answer 38

confocal scanning laser microscope

Question 39

what is the resolution of a confocal scanning laser microscope?

Answer 39

0.1 micrometers resolution

Question 40

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

Answer 40

electron microscope

Question 41

name 2 types of electron microscopes

Answer 41

transmission electron microscope scanning electron microscope TEM and SEM

Question 42

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

Answer 42

electromagnets | vacuum

Question 43

is the magnification of transmission electron microscope high? what is the resolution?

Answer 43

yes its high magnification resolution= 0.2 nanometers

Question 44

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

Answer 44

sliced thin and must be stained

Question 45

what level of visualization does the transmission electron microscope allow?

Answer 45

the molecular level

Question 46

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

Answer 46

specimen is coated with a thin layer of heavy metal

Question 47

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

Answer 47

scanning electron microscopy

Question 48

How does the SEM work?

Answer 48

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

Question 49

what type of microscope can scan large specimens? what is the magnification range?

Answer 49

SEM range of magnification: 15-100,000 times