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BIOL 2330 - microbiology > study of microbial structure (microscopes) > Flashcards

study of microbial structure (microscopes) Flashcards

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Biology 101 flashcards
1
Q

who was the first person to observe/discover microbes

A

Antonie van Leeuwenhoek

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2
Q

how does the light microscope view objects

A

uses visible light

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3
Q

list the types of light microscopes

A

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

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4
Q

which type of microscope is the most common

A

compound

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5
Q

define compound microscope

A

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

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6
Q

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

A

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

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7
Q

what does bright field look like

A

a dark image against a brighter background

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8
Q

how does bright field work

A

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

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9
Q

how do we calculate total magnification

A

mag of objective x mag of eyepiece

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10
Q

define resolution

A

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

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11
Q

what is the term for a microscope that has good resolution

A

we say it has good resolving power

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12
Q

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

A

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

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13
Q

what is one factor that influences resolution

A

angular aperture

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14
Q

what is the angular aperture

A

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

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15
Q

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

A

increasing magnification increases the angular aperture = high resolution

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16
Q

what is the formula that determines the resolution of a microcope

A

d = 0.5(lambda)/n sin theta

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17
Q

what is theta in the resolution equation

A

angular aperture

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18
Q

what is lambda in the resolution equation

A

wavelength of light

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19
Q

what is n in the resolution equation

A

refractive index

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20
Q

what is n sin theta in the resolution equation

A

numerical aperture

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21
Q

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

A

d = small
lambda = small
n = big

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22
Q

how can we achieve maximum resolution on a bright field microscope

A

use the 100x objective lens with oil immersion

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23
Q

how does oil immersion increase resolution

A

it increases the refractive index

24
Q

define refractive index

A

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

25
Q

describe how oil immersion increases the refractive index

A

it bends more light towards the objective lens

26
Q

what is the refractive index for oil? air?

A

oil = 1.5
air = 1.0

27
Q

what is the max resolution using bright field without oil immersion

A

300 nm

28
Q

what is the refractive index for bright field with oil immersion

A

200 nm

29
Q

advantages of bright field

A

inexpensive, easy to use

30
Q

disadvantages of bright field

A

specimen must have color

31
Q

what is bright field useful for

A

viewing dead + stained cells

32
Q

which light microscopes can be used to view living specimens

A

dark field, phase contrast, differential interference, confocal

33
Q

how does a dark field image look

A

light specimen against a dark background

34
Q

describe how internal structures appear with dark field vs bright field

A

dark field allows us to see internal structures more clearly

35
Q

describe how dark field works

A

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

36
Q

what is dark field useful for

A

observing detailed images of live, unstained organisms

37
Q

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

A

true

38
Q

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

A

False: they can be unstained

39
Q

what do phase contrast microscopes do

A

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

40
Q

what are the extra components of a phase contrast microscope

A

annular diaphragm and a phase plate in the objective lense

41
Q

uses of phase contrast?

A

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

42
Q

describe differential interference microscope + how it works

A

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

43
Q

what type of image do we get with differential interference

A

3D coloured images

44
Q

describe fluorescence microscope + how it works

A

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

45
Q

uses of fluorescent microscope?

A

can be used to identify bacterial pathogens

46
Q

how does confocal microscope work

A

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

47
Q

what type of image to we get with confocal

A

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

48
Q

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

A

use electrons as a source of illumination instead of light

49
Q

what are the two types of electron microscopes

A

transmission electron (TEM)

scanning electron (SEM)

50
Q

describe TEM + what we look at with it

A

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

51
Q

describe SEM + what we look at with it

A

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

52
Q

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

A

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

53
Q

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

A

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

54
Q

what are the two types of scanning probe microscopes

A

scanning tunneling

atomic force

55
Q

describe scanning tunneling microscope

A

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

56
Q

what can we see with a scanning tunneling mic.

A

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

57
Q

describe atomic force mic.

A

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

BIOL 2330 - microbiology (30 decks)

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