Observing Microbes- Test 1

Question 1

What is the size of red blood cells?

Answer 1

5 um

Question 2

What is the size of E.coli bacteria?

Answer 2

1 um

Question 3

What is the size of T-even bacterio-phages (viruses)?

Answer 3

60 nm

Question 4

What is the size of DNA double helix?

Answer 4

20 nm

Question 5

The ability to enlarge objects

Answer 5

magnification

Question 6

ability to show detail

Answer 6

resolving detail

Question 7

a measure of how greatly a substance slows the velocity of light

Answer 7

refractive index

Question 8

What happens to the light when its lower to higher RF?

Answer 8

it is slowed and bent toward normal

Question 9

What happens to the light when its higher to lower RF?

Answer 9

it is sped up and bent away from normal

Question 10

the ability to distinguish two adjacent objects; a function of wavelength of light that forms the image along with characteristics of objectives

Answer 10

resolution

Question 11

What is the symbol for resolving power?

Answer 11

d

Question 12

What is the symbol for visible light (400-70 nm)?

Answer 12

the upside down y

Question 13

What is the symbol for the reflective index?

Answer 13

n

Question 14

What is the symbol for half the angle of the cone of light entering the lens?

Answer 14

delta

Question 15

the light-bending ability of a medium

Answer 15

refractive lens

Question 16

The light may bend in air so much that it misses what?

Answer 16

The small high-magnification lens

Question 17

What is used to keep light from bending?

Answer 17

immersion oil

Question 18

-most widely used
-specimen is darker than surrounding field

Answer 18

bright-field

Question 19

-brightly illuminated specimens surrounding by dark field
-live and unstained specimens

Answer 19

dark-field

Question 20

-transform subtle changes in light waves passing through the specimen into differences in light intensity, best for observing intracellular structures
-accentuates diffraction of the light that passes through a specimen

Answer 20

phase-contrast

Question 21

-separates the light source into two beams (two refractive indices) giving the appearance of a three-dimensional physical relief
-accentuates diffraction of light that passes through a specimen; uses two beams of light

Answer 21

differential interference contrast

Question 22

-light objects are visible against a dark background
-light reflected off or refracted through the specimen enters the objective lens

Answer 22

darkfield illumination

Question 23

-exposes specimen to ultraviolet, violet, or blue light
-fluorescent substances absorb UV light and emit visible light
-cells may be stained with fluorescent dyes (fluorochromes)

Answer 23

Fluorescent microscopy

Question 24

-uses fluorochromes and a laser light
-the laser illuminates each plane in a specimen to produce a three-dimensional image

Answer 24

Confocal Fluorescence Microscopy

Question 25

-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

Answer 25

Electron microscopes

Question 26

preserves internal and external structures and fixes them in position

Answer 26

specimen preparation

Question 27

-routine use with bacteria and archaea
-preserves overall morphology but not internal structures

Answer 27

heat fixation

Question 28

-used with larger, more delicate organisms
-protects fine cellular substructure and morphology

Answer 28

chemical fixation

Question 29

cells that retain a basic stain in the presence of acid-alcohol

Answer 29

acid-fast

Question 30

-non-acid fast cells lose the basic stain when rinsed with acid-alcohol, and are usually counterstained (with a different color basic stain) to see them

Answer 30

acid fast stain

Question 31

What are types of special stains and what do they do?

Answer 31

-negative staining- useful for capsules
-endospore staining- heat is required to drive a stain into the endospore
-flagella staining- requires a mordant to make the flagella wide enough to see