Ch. 2 - Viewing the Microbial World

Question 1

Bacteria and protozoa are expressed in ___

Answer 1

micrometers

Question 2

Typical size of coccus bacteria

Answer 2

~ 1 um diameter

Question 3

Typical size of bacilis bacteria

Answer 3

1um x 3um

Question 4

Viruses are expressed in ____

Answer 4

nanometers

Question 5

Most disease causing viruses are ___ long

Answer 5

10-300nm

Question 6

Length of ebola virus

Answer 6

1000nm (1um)

Question 7

Measurements

Answer 7

1m = 100cm = 1000mm = 1 000 000um = 1 000 000 000nm

Question 8

DF microscope

Answer 8

an optical instrument used to observe tiny objects. Objects so small they cannot be seen with the unaided human eye.

Question 9

Resolving power/ Resolution

Answer 9

The limit to what can be seen using that optical instrument

Question 10

Resolving power of the unaided human eye

Answer 10

0.2 mm

Question 11

Resolving power of compound microscope

Answer 11

0.2um

Question 12

Objects cannot be seen if they are _____

Answer 12

half a wavelength of visible light (0.45um)

Question 13

Total magnification of microscope=

Answer 13

ocular lens (10) x objective lens (4,10,40,100)

Question 14

Photomicrographs

Answer 14

Pictures taken through the lens system of the compound light microscope

Question 15

Bright field compound microscope

Answer 15

Field is bright

Question 16

Dark field compound microscope

Answer 16

Field is dark and the object lights up

Question 17

Phase contrast microscope

Answer 17

• observes unsustained LIVING microorganisms

- organisms are more easily seen because light refracted by living cells is different than by the medium

Question 18

Fluorescence microscopes

Answer 18

• have a built in UV light source
• When UV light strikes certain dyes/pigments, the substances emit a longer wavelength, leading to a glow
• Can use florescent tags to light up certain parts of DNA

Question 19

3 key aspects of Electron microscopes

Answer 19

1- high resolving power: enables us to see extremely small microbes (viruses)
2- cant observe living organisms because the process kills them
3- Electron beam = source of illumination

Question 20

Tranmission Electron Microscope

Answer 20

• beams of electrons THROUGH a thick specimen (>1um)
• Get to see inside the cell
• image is produced on phsphor-coated screen
• resolving power 0.2nm
• magnification 1000x greater than compound microscope

Question 21

Scanning Electron Microscope

Answer 21

• Electrons are bounced off the surface of the specimen to produce an image on a monitor
• get to observe the outter surface, like an X ray (shape, clumping…)
• RP less than transmission

Question 22

Atomic Force Microscopy

Answer 22

• morphology and microorganisms via attractive forces between the specimen and the tip might distort the specimen