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2.1 Cell Structure > 2.1.1 Microscopes > Flashcards

2.1.1 Microscopes Flashcards

1
Q

resolution definition

A

the degree to which it is possible to distinguish two objects, which are very close together

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2
Q

magnification definition

A

how many times bigger the image of a specimen observed is, compared to the actual size of the specimen

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3
Q

magnification equation

A

magnification=size of image/size of actual

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4
Q

method for using light microscope: 9 steps

A
  1. Prepare sample using a glass slide, coverslip and stain
  2. Plug microscope into plug socket and turn on
  3. Turn light on
  4. Put sample on the stage, secure with clips
  5. Adjust to lowest magnification
  6. Move stage all the way up
  7. Use the coarse focus wheel to get sample into focus (larger field of view)
  8. Move to next objective lens (use fine focus wheel to show detail)
  9. Repeat with next objective lens
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5
Q

light microscope: how does it work?

A

it works by passing light through a specimen and focusing the light on an eyepiece or camera, which magnifies the image.

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6
Q

light microscope: what is it used for?

A

-schools and colleges
-hospitals
-universities

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7
Q

light microscope: preparation of specimen

A

place a slide with cover slip and with a stain

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8
Q

light microscope: maximum magnification

A

x1500

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9
Q

light microscope: 2D or 3D, colour or black and white

A

2D, colour

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10
Q

light microscope: resolution

A

0.2 μm

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11
Q

light microscope: advantages 4

A

-relatively cheap
-easy to use
-portable
-able to study whole living specimen

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12
Q

light microscope: disadvantage 1

A

-resolution is limited (as cannot increase magnification any higher with detail)

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13
Q

confocal laser scanning microscope: how does it work?

A

a thick section of tissue or small living organisms are scanned with a laser beam
the laser beam is reflected by the fluorescent dyes
multiple depths of the tissue section/organisms are scanned to produce an image
(think of it like the laser beam is building up the image layer by layer)

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14
Q

confocal laser scanning microscope: what is it used for?

A

-medical professions
-branches of biological research

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15
Q

confocal laser scanning microscope: preparation of specimen

A

the cells being viewed must be stained with fluorescent dyes

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16
Q

confocal laser scanning microscope: max magnification

A

not needed

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17
Q

confocal laser scanning microscope: 2D or 3D, colour or black and white

A

3D, colour

18
Q

confocal laser scanning microscope: resolution

A

do not need

19
Q

confocal laser scanning microscope: advantages 4

A

-they can be used on thick or 3-D specimens
-they allow the external, 3-D structure of specimens to be observed
-very clear images are produced, the high resolution is due to the fact that the laser beam can be focused at a very specific depth

20
Q

confocal laser scanning microscope: disadvantages 2

A

-it is a slow process and takes a long time to obtain an image
-the laser has the potential to cause photodamage to the cells

21
Q

transmission electron microscope (TEM): how does it work?

A

use electromagnets to focus a beam of electrons, this beam of electrons is transmitted through the specimen
denser parts of the specimen absorb more electrons tf denser parts appear darker on the final image produced (produces contrast between different parts of the object being observed)

22
Q

transmission electron microscope (TEM): what is it used for?

A

-biological research

23
Q

transmission electron microscope: preparation of specimen

A

the specimen have to be chemically fixed by being dehydrated and stained with metal salts, stained in order to absorb the electrons (heavy metal compounds are often used)

24
Q

transmission electron microscope (TEM): max magnification

A

up to x 2 million

25
Q

transmission electron microscope (TEM): 2D or 3D, colour or black and white

A

2D, black and white

26
Q

transmission electron microscope (TEM): advantages 2

A

-high resolution
-this allows the internal structures within cells (or even within organelles) to be seen

27
Q

transmission electron microscope (TEM): disadvantages 6

A

-specimen cannot be alive (as there is a vacuum inside of TEM, all water must be removed from specimen)
-large
-very expensive
-need a great deal of skills and training to use
-they can only be used with very thin specimens or thin sections of the object being observed
-the lengthy treatment required to prepare specimens means that artefacts can be introduced (artefacts look like real structures but are actually the results of preserving and staining)

28
Q

scanning electron microscope (SEM): how does it work?

A

SEMs scan a beam of electrons across the specimen
This beam bounces off the surface of the specimen and the electrons are detected, forming an image
Tf SEMs can produce three-dimensional images that show the surface of specimens

29
Q

scanning election microscope (SEM): what are they used for?

A

biological research

30
Q

scanning electron microscope (SEM): preparation of specimen

A

specimen has to be placed in a vacuum and often coated with a fine film of metal

31
Q

scanning electron microscope (SEM): max magnification

A

up to 200,000x

32
Q

scanning electron microscope (SEM): 2D or 3D, colour or black and white

A

3D, black and white
(the computer programme can add false colour

33
Q

what type of instruments are microscopes?

A

optical

34
Q

what scale is used for microscopes?

A

logarithmic

35
Q

what does logarithmic mean?

A

it goes up in steps, where each is 10-fold increase

36
Q

what is the effect of increasing magnification,on resolution?

A

increasing magnification, doesn’t increase resolution

37
Q

why does light limit resolution in light microscopes?

A

it is impossible to resolve two objects that are closer than half the wavelength of light
(the wavelength of visible light is between 0.5 or 0.65),

38
Q

what can a light microscope observe?

A

eukaryotic cells, their nuclei and possibly mitochondria and chloroplasts

39
Q

scanning electron microscopes (SEMs): 2 advatages

A

-they can be used on thick or 3-D specimens
-they allow the external, 3-D structure of specimens to be observed

40
Q

scanning electron microscopes (SEMs): 3 disadvantages

A

-they give lower resolution images than TEMs
-they cannot be used to observe live specimens
-they do not produce a colour image

41
Q

what should be used to calibrate a microscope?

A

a stage micrometer

2.1 Cell Structure (7 decks)

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