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Bio L6 (2) DNA and cells > Microscopy > Flashcards

Microscopy Flashcards

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1
Q

Explain why an electron microscope would be required to see the detailed structure of organelle Y.

A
  • Needs a higher resolution;
  • In order to distinguish between very close structures;
  • Due to the shorter wavelength of electron beam.
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2
Q

An electron microscope has a much greater resolving power than an optical microscope.
Explain the meaning of the term resolving power.

A

The ability to distinguish from points (close together).

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3
Q

An electron microscope has a much greater resolving power than an optical microscope.
Explain the reasoning for this difference.

A

Electrons have a shorter wavelength than light.

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4
Q

Explain why it is possible to see the detailed structure of a prokaryotic cell with an electron microscope but not with a light microscope.

A

Electron microscope has a better resolution / able to distinguish between points more clearly;
Electron beam has a shorter wavelength.

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5
Q

Care must be taken in interpreting electron micrographs. Some features visible in an electron micrograph may not be present in the living cell, explain why?

A

Processes involved in the preparation may alter / distort the cell contents.

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6
Q

What is the magnification equation?

A

Magnification = Image size / Real object size.

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7
Q

What is the magnification?

A

How much bigger the image is than the specimen.

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8
Q

What is the resolution?

A

How detailed the image is, it is how well a microscope distinguishes between two close points.

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9
Q

If a microscope can’t separate two objects, what will further increasing the magnification do?

A

It will have no effect because the resolution stays the same.

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10
Q

If a microscope can’t separate two objects, what will further increasing the resolution do?

A

It will allow you to distinguish from closer points.

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11
Q

What are the two main type of microscope?

A

Optical (light) and Electron.

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12
Q

Which type of microscope uses light beams?

A

Optical microscopes.

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13
Q

Which type of microscope uses electron beams?

A

Electron microscopes.

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14
Q

Which type of microscope has a higher resolution?

A

Electron microscopes.

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15
Q

Why does the electron microscope have a higher resolution?

A

Because the wavelength of electrons are shorter than the wavelength of light.

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16
Q

Which type of microscope has a lower resolution?

A

Optical microscopes.

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17
Q

Which type of microscope gives a more detailed image?

A

Electron microscopes.

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18
Q

Which microscope is often used to look at organelles within cells?

A

Electron microscopes.

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19
Q

Which microscope has a resolution of about 0.2 micrometers (um)?

A

Optical microscope.

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20
Q

Which microscope has a resolution of about 0.0002 micrometers (um)?

A

Electron microscope.

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21
Q

What is the resolution of an electron microscope?

A

0.0002 micrometers (um).

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22
Q

What is the resolution of an optical microscope?

A

0.2 micrometers (um).

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23
Q

Which microscopes can you see the nucleus through?

A

Both optical and electron.

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24
Q

How much greater is the maximum resolution of an electron microscope than an optical microscope.

A

1000x higher, 0.0002um instead of 0.2um.

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25
Q

What is the maximum useful magnification of an optical microscope?

A

x1,500.

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26
Q

What is the maximum useful magnification of an electron microscope?

A

x1,500,000.

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27
Q

Compare the maximum useful magnification of an optical microscope and an electron microscope.

A 
Optical = x1,500.
Electron = x1,500,000.
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28
Q

What are the two types of Electron Microscope?

A

Transmission electron microscope (TEMs) and Scanning electron microscope (SEMs).

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29
Q

Which type of microscope uses electromagnets to focus a beam of electrons?

A

Transmission electron microscopes (TEMs).

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30
Q

In TEMs, what happens to the focused beam of electrons?

A

It is passed through the specimen.

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31
Q

In TEMs, how is the electron beam focused?

A

Through the use of electromagnets.

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32
Q

In TEMs, what makes the specimen appear different colours?

A

Dense parts of the specimen absorb more electrons making them look darker.

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33
Q

Which type of microscope can only be used with thin specimens?

A

Transmission electron microscopes (TEMs).

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34
Q

Which type of electron microscope has a higher resolution?

A

TEMs have a higher resolution than SEMs.

35
Q

What are the advantages of TEMs?

A

High resolution so you can see the internal structure of organelles like chloroplasts.

36
Q

What are the disadvantages of TEMs?

A

Thin specimens.

37
Q

What are the advantages of SEMs?

A

Can be used on thick specimens.

38
Q

What are the disadvantages of SEMs?

A

Lower resolution than TEMs.

39
Q

Which type of microscope should be used on a thick specimen?

A

Scanning electron microscope (SEM).

40
Q

How do SEMs work?

A

They scan a beam of electrons across the specimen, knocking off electrons from the specimen, gathered in a cathode ray tube to form an image.

41
Q

Which microscope used a cathode ray tube?

A

Scanning electron miscroscope (SEM).

42
Q

Which microscope creates a 3-D image?

A

Scanning electron microscope (SEMs) produce 3-D images of the surface of a specimen.

43
Q

How do you prepare a ‘temporary mount’ of a specimen on a slide?

A
  • Pipetting a small drop of water onto the slide.
  • Add a drop of stain.
  • Add a cover slip making sure there are no air bubbles.
44
Q

What are slides? (In an optical microscope)

A

Strips of clear glass or plastic.

45
Q

What are stains used for? (In an optical microscope)

A

They are used to highlight objects in a cell.

46
Q

What is the function of an eosin stain? (In an optical microscope)

A

To make the cytoplasm show up.

47
Q

What is the function of an iodine stain? (In an optical microscope)

A

To stain starch grains in plant cells.

48
Q

What is the function of the eyepiece? (In an optical microscope)

A

You look down it.

49
Q

What is the function of the coarse adjustment knob? (In an optical microscope)

A

To bring the specimen roughly into focus.

50
Q

What is the function of the fine adjustment knob? (In an optical microscope)

A

To finely tune the focus.

51
Q

What is the function of the stage? (In an optical microscope)

A

Where the microscope slide is placed.

52
Q

What is the function of the light? (In an optical microscope)

A

To allow you to see through the specimen.

53
Q

What are the high and low power objective lenses? (In an optical microscope)

A

They are used to magnify the objective.

54
Q

The detailed ultrastructure of cells was revealed in the 1950’s, what caused this discovery?

A

The introduction of electron microscopes.

55
Q

What is the name for the image created by the electron microscopes?

A

Electron micrographs.

56
Q

What does a microscope do?

A

Produce a magnified image of an object or specimen.

57
Q

Who created the first microscope powerful enough to explore microbes?

A

Anton van Leeuwenhoek (1632-1723).

58
Q

How does a compound light microscope work?

A

Light passes through the specimen and then through two sets of glass lenses, the objective lens and ocular or eyepiece lens, they refract the light to give a magnified image of the object.

59
Q

If the image in an optical microscope is projected onto a photographic film, what is the name given to the result?

A

A photomicrograph or a light micrograph.

60
Q

What is a photomicrograph?

A

A photograph taken inside an optical microscope.

61
Q

What is resolving power?

A

The limit of effective magnification, where a microscope can show two objects as seperate.

62
Q

Which microscopes can be used to see mitochondrion?

A

Light and Electron microscopes.

63
Q

Which microscopes can be used to see a virus?

A

Electron microscopes.

64
Q

Which microscopes can be used to see plant and animal cells?

A

Light and Electron microscopes.

65
Q

Which microscopes can be used to see ribosomes?

A

Electron microscopes.

66
Q

Which microscopes can be used to see protein molecules?

A

Electron microscopes.

67
Q

Which microscopes can be used to see lipid microscopes?

A

Electron microscopes.

68
Q

Which microscopes can be used to see most bacterium?

A

Light and Electron microscopes.

69
Q

Compare the wavelengths of light beams and electron beams?

A

Electron beams have much shorter wavelengths.

70
Q

Which type of microscope would you use for performing a count of white blood cells from the blood of a person with an infection?

A

Compound light microscope.

71
Q

Which type of microscope would you use for resolving the ultrastructure of a chloroplast?

A

Transmission electron microscope (TEM).

72
Q

Which type of microscope would you use for distinguishing extinct plant species on the basis of pollen surface features?

A

Scanning electron microscope (SEM).

73
Q

Which type of microscope would you use for counting the heart rate and rate of limb beating in a water flea?

A

Dissecting microscope.

74
Q

Which microscopes can be used for living specimens?

A

Compound light microscopes.

75
Q

How is the specimen prepared for a SEM microscope?

A

It must be non-living and supported on a metal disc in a vacuum.

76
Q

How is the specimen prepared for a TEM microscope?

A

It must be non-living and supported on a small copper grid in a vacuum.

77
Q

How is the specimen prepared for a light microscope?

A

It can be living or dead, supported on a glass slide.

78
Q

Which has a higher maximal resolution, TEM or SEM?

A

TEM.

79
Q

What stains are used in an optical microscope?

A

Coloured dye, a surface or section.

80
Q

What stains are used in a transmission electron microscope?

A

impregnated with heavy metals.

81
Q

What stains are used in a scanning electron microscope?

A

Coated with carbon or gold.

82
Q

The book micrographia contained details of the first compound microscope, who created this?

A

Robert Hooke (1660’s).

83
Q

What are the cost differences between an optical microscope and an electron microscope?

A

Optical is low cost and electron is high cost.

Bio L6 (2) DNA and cells (8 decks)

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