Ch.4: Microscopy, staining and classification

Question 1

what are the general principles of microscopy?

Answer 1

Wavelength
magnification
resolution
contrast

Question 2

what is wavelength of radiation?

Answer 2

distance between corresponding waves

Question 3

what waves are very short

Answer 3

gamma rays 10-12 m

Question 4

can humans see in the visible spectrum

Answer 4

yes

Question 5

what waves are very long

Answer 5

Infrared rays

Question 6

Microscopes can use different wavelengths to increase what?

Answer 6

resolving power

Question 7

what is magnification?

Answer 7

-the apparent increase in size and object
-occurs when the beam of radiation refracts through a lens

Question 8

what is clarity determined by

Answer 8

resolution and contrast

Question 9

what is resolution?

Answer 9

the ability to distinguish objects that are close together

Question 10

what is contrast

Answer 10

-the difference in intensity between two objects and the background
-important helps determine resolution
-staining helps to increase contrast

Question 11

who created the simple microscope?

Answer 11

Van Leeuwenhoek

Question 12

what are the types of light microscopy?

Answer 12

-bright field
-dark field
-phase contrast
-nomarski

Question 13

what is bright field?

Answer 13

-Light passes through the specimen and into the lens.
-Dark specimen on a bright background.
-Created by the specimen absorbing or scattering light.

Question 14

whats is total magnification?

Answer 14

objective lense X ocular lense

Question 15

what is the ocular lens

Answer 15

magnifies the image formed by the objective lens seen by the human eye

Question 16

what happens when immersion oil is used?

Answer 16

more light enters lens

Question 17

what is the body

Answer 17

transmits the image from the objective lens to the ocular lens using prisms

Question 18

what are objective lenses

Answer 18

primary lenses that magnify the specimen

Question 19

what is the stage

Answer 19

holds the microscope slide in position

Question 20

what is the condenser

Answer 20

focuses light through the specimen

Question 21

what is the diaphragm

Answer 21

controls the amount of light entering the condenser

Question 22

what is the illuminator

Answer 22

light source

Question 23

what is the coarse focusing knob

Answer 23

moves the stage up and down to focus the image

Question 24

what is the fine focusing knob

Answer 24

slightly moves the stage up and won for focusing

Question 25

what is the dark field?

Answer 25

-The sample appears bright against a dark background, enhancing contrast without staining. -best for pale objects

Question 26

what is phase contrast?

Answer 26

used to examine living specimens and internal structures of living organisms

Question 27

how is contrast created

Answer 27

light waves out of a phase

Question 28

in phase

Answer 28

brighter

Question 29

out of phase

Answer 29

darker

Question 30

what is fluorescence in light microscope?

Answer 30

direct UV light source at specimen -specimen radiates energy back at a longer visible wavelength -UV light increases resolution and contrast -some cells need to be stained and some are naturally fluorescent

Question 31

what is an electron microscope

Answer 31

uses electron beams instead of light to magnify objects at much higher resolutions -done under vacuum; not for living microbes

Question 32

what is a Scanning electron microscope (SEM)

Answer 32

produce a 3-D view of the microbe's surface and cellular structures

Question 33

what is transmission electron microscopes (TEM)

Answer 33

produces a 2-D view to view internal ultra-cellular detail

Question 34

what are acidic dyes

Answer 34

(negative charge) stain alkaline structures (+ charge) ex: eosin binds + charges (amino acids)

Question 35

what are basic dyes

Answer 35

(positive charge) stain acidic structure ( - charge)

Question 36

what are the most common dyes

Answer 36

-crystal violet -methylene blue -safranin

Question 37

how do you prepare a simple stain?

Answer 37

-a very thin film of the specimen on glass slide -allow to air dry -heat fix -kills any live bacteria -induces coagulation of proteins to "stick" the bacteria to the slide -Helps prevent bacterial smear from washing off during procedure -only uses one dye

Question 38

gram positve cells stain what color?

Answer 38

purple

Question 39

gram negative cells stain what color?

Answer 39

pink/red

Question 40

what does a primary stain do?

Answer 40

stains all cells

Question 41

what is mordant?

Answer 41

binds to the dye and makes it less soluble (stays in the cell wall)