study of microbial structure (microscopes)

Question 1

who was the first person to observe/discover microbes

Answer 1

Antonie van Leeuwenhoek

Question 2

how does the light microscope view objects

Answer 2

uses visible light

Question 3

list the types of light microscopes

Answer 3

bright-field, dark-field, phase contrast, differential interference, fluorescence, confocal

Question 4

which type of microscope is the most common

Answer 4

compound

Question 5

define compound microscope

Answer 5

they make use of several lenses in combination to enlarge an image

Question 6

what elements are needed to form an image regardless of the type of microscope used

Answer 6

source of illumination, specimen, system of lenses that focus the illumination on the specimen and form the image

Question 7

what does bright field look like

Answer 7

a dark image against a brighter background

Question 8

how does bright field work

Answer 8

light travels from the source of illumination through the condenser, through the specimen, through the objective lens, and through the eyepiece to the eye of the observer

Question 9

how do we calculate total magnification

Answer 9

mag of objective x mag of eyepiece

Question 10

define resolution

Answer 10

ability of a lens to distinguish between small objects that are close together

Question 11

what is the term for a microscope that has good resolution

Answer 11

we say it has good resolving power

Question 12

define what it means for a microscope to have high resolving power

Answer 12

it has a high resolution (ability to distinguish between two objects)

Question 13

what is one factor that influences resolution

Answer 13

angular aperture

Question 14

what is the angular aperture

Answer 14

the measure of how much light is leaving the specimen and enters the eyepiece

Question 15

in terms of magnification, how do we get high angular aperture

Answer 15

increasing magnification increases the angular aperture = high resolution

Question 16

what is the formula that determines the resolution of a microcope

Answer 16

d = 0.5(lambda)/n sin theta

Question 17

what is theta in the resolution equation

Answer 17

angular aperture

Question 18

what is lambda in the resolution equation

Answer 18

wavelength of light

Question 19

what is n in the resolution equation

Answer 19

refractive index

Question 20

what is n sin theta in the resolution equation

Answer 20

numerical aperture

Question 21

in the resolution equation, what sizes do we want d, lambda, and n to be

Answer 21

d = small
lambda = small
n = big

Question 22

how can we achieve maximum resolution on a bright field microscope

Answer 22

use the 100x objective lens with oil immersion

Question 23

how does oil immersion increase resolution

Answer 23

it increases the refractive index

Question 24

define refractive index

Answer 24

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

Question 25

describe how oil immersion increases the refractive index

Answer 25

it bends more light towards the objective lens

Question 26

what is the refractive index for oil? air?

Answer 26

oil = 1.5 air = 1.0

Question 27

what is the max resolution using bright field without oil immersion

Answer 27

300 nm

Question 28

what is the refractive index for bright field with oil immersion

Answer 28

200 nm

Question 29

advantages of bright field

Answer 29

inexpensive, easy to use

Question 30

disadvantages of bright field

Answer 30

specimen must have color

Question 31

what is bright field useful for

Answer 31

viewing dead + stained cells

Question 32

which light microscopes can be used to view living specimens

Answer 32

dark field, phase contrast, differential interference, confocal

Question 33

how does a dark field image look

Answer 33

light specimen against a dark background

Question 34

describe how internal structures appear with dark field vs bright field

Answer 34

dark field allows us to see internal structures more clearly

Question 35

describe how dark field works

Answer 35

an opaque disk causes a hollow cone of light to pass through the specimen, so only light going through is what goes through the objective lens

Question 36

what is dark field useful for

Answer 36

observing detailed images of live, unstained organisms

Question 37

T or F: cells need to be stained for bright field

Answer 37

true

Question 38

T or F: cells need to be stained for dark field

Answer 38

False: they can be unstained

Question 39

what do phase contrast microscopes do

Answer 39

exploit differences between the thickness and refractive indices of various regions of a cell to increase contrast = dif levels of brightness

Question 40

what are the extra components of a phase contrast microscope

Answer 40

annular diaphragm and a phase plate in the objective lense

Question 41

uses of phase contrast?

Answer 41

looking at live, unstained cells, widely used to study eukaryotes and detect bacterial cell structures such as endospores and inclusions

Question 42

describe differential interference microscope + how it works

Answer 42

similar to phase contrast but more sensitive. it makes use of prisms to split up light beams

Question 43

what type of image do we get with differential interference

Answer 43

3D coloured images

Question 44

describe fluorescence microscope + how it works

Answer 44

uses UV light as illumination source, and this is used to excite fluroescence in the specimen

Question 45

uses of fluorescent microscope?

Answer 45

can be used to identify bacterial pathogens

Question 46

how does confocal microscope work

Answer 46

makes use of lasers to illuminate a specimen, usually one that's been fluorescently labelled. Lasers move plane by plane and then send this info to a computer

Question 47

what type of image to we get with confocal

Answer 47

we get a stack of images to form a 3D image

Question 48

describe electron microscopes + how they're different from light microscopes

Answer 48

use electrons as a source of illumination instead of light

Question 49

what are the two types of electron microscopes

Answer 49

transmission electron (TEM) scanning electron (SEM)

Question 50

describe TEM + what we look at with it

Answer 50

forms an image from electrons that are transmitted from the specimen. Used to look at internal cell structures

Question 51

describe SEM + what we look at with it

Answer 51

forms an image from electrons that are deflected from the specimen's outer surface. Used to look at surface topology of the cell = 3D image

Question 52

list the strengths of an electron microscope compared to a light microscope

Answer 52

has better magnification (100,000x vs 1000x), has better resolution (0.2nm vs 200nm)

Question 53

list the weaknesses of an electron microscope compared to a light microscope

Answer 53

cannot look at living specimens, time consuming + difficult to prepare specimens, requires technical expertise, machine is large and expensive

Question 54

what are the two types of scanning probe microscopes

Answer 54

scanning tunneling atomic force

Question 55

describe scanning tunneling microscope

Answer 55

makes use of a probe to measure all the bumps and depressions of the surface

Question 56

what can we see with a scanning tunneling mic.

Answer 56

can see the surface topology, individual atoms, specimens imersed in water

Question 57

describe atomic force mic.

Answer 57

can be used to look at surfaces that do not conduct electricity very well, can look at proteins