Chapter 2

Question 1

micrometer

Answer 1

• um
• one millionth of a meter
• size of bacteria and protozoa

Question 2

size of spherical bacterium

Answer 2

• approx 1 um in diameter

Question 3

size of rod-shaped bacterium

Answer 3

• approx 1 um wide and 3 um long

Question 4

nanomemeters

Answer 4

• nm
• one billionth of a meter
• size of viruses

Question 5

range of virus sizes that cause human disease

Answer 5

10-300 nm

Question 6

Ebola virus size

Answer 6

can be as long as 1000 nm aka 1 um

Question 7

ocular micrometer

Answer 7

how microorganisms are measured using a microscope

Question 8

microscope

Answer 8

• optical instrument used to observe tiny objects that can’t be seen with unaided human eye

Question 9

resolving power/resolution

Answer 9

the limit as to what can be see using an optical instrument

Question 10

resolving power of unaided human eye

Answer 10

0.2 mm

Question 11

simple microscope

Answer 11

• contains one magnifying lens
• magnifying glass = 3-20x larger
• Leeuwenhoek’s simple microscope mad max magnifying power of 300x

Question 12

compound microscope (compound light microscope)

Answer 12

• contains more than one magnifying lens

- usually magnify objects about 1000x

Question 13

resolving power of compound microscope

Answer 13

0.2 um

Question 14

what limits the size of an object that can be seen?

Answer 14

• the wavelength of visible light which is about 0.45 um

- objects can’t be seen if they are smaller than half the wavelength of visible light

Question 15

todays lab microscopes

Answer 15

• eyepiece/ocular lens is usually 10x

- objective lens commonly 4x, 10x, 40x, and 100x

Question 16

total magnification calculation

Answer 16

• total magnification = ocular lens x objective lens

—> 10x ocular x 10x objective = 100x total magnification

Question 17

photomicrographs

Answer 17

photographs taken through the lens of the compound light microscope

Question 18

brightfield microscope

Answer 18

• objects observed against a bright background or “bright field”
• dark objects seen against illuminated background

Question 19

dark field microscope

Answer 19

• objects observed against a dark background or “dark field”

- illuminated objects seen against dark background

Question 20

other types of compound microscopes

Answer 20

• phase-contrast

- fluorescent

Question 21

phase-contrast microscope

Answer 21

• used to observe unstained living microorganisms
• light refracts off of living cells is different from the light refracted off of surrounding medium
• makes organisms more easily seen

Question 22

fluorescence microscopes

Answer 22

• contains built in UV light
• fluorescent dye tags attach to cells
• UV light strikes dye and causes substance to emit longer wavelength causing them to glow against dark background

Question 23

electron microscopes

Answer 23

• can see extremely small microbes like rabies and smallpox
• electron beam used as source of illumination and magnets focus the beam
• much higher resolving power than compound light microscopes

Question 24

why can’t living organisms be observed using an electron microscope

Answer 24

the procedure kills the organism

Question 25

two types of electron microscopes

Answer 25

• transmission

- scanning

Question 26

transmission electron microscope

Answer 26

• uses electron gun to fire electron beam through <1 um thick specimen
• image produced on phosphor-coated screen
• magnification approx 1000x greater than compound light microscope

Question 27

resolving power of transmission electron microscope

Answer 27

0.2 nm

Question 28

scanning electron microscope

Answer 28

• electrons bounced off surface of specimen and appears on monitor
• used to observe outer surfaces of specimens

Question 29

resolving power of scanning electron microscope

Answer 29

100x less than transmission electron microscope