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Biology 2.1.1: Cell Structure > microscopy > Flashcards

microscopy Flashcards

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1
Q

how does an optical microscope work?

A

light from a light source underneath the specimen passes through the specimen

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2
Q

what is the resolution of an optical microscope?

A

200nm

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3
Q

what is the magnification of an optical microscope?

A

x1500

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4
Q

what are the strengths of optical microscopes?

A
  • colour image
  • uses live specimens
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5
Q

what are the weaknesses of optical microscopes?

A
  • poor resolution
  • 2D image
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6
Q

what do optical microscopes allow us to see?

A

whole cells/tissues

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7
Q

how does a transmission electron microscope work?

A

electrons are transmitted through a specimen and denser parts of the specimen absorb more electrons, becoming darker

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8
Q

what is the resolution of a TEM?

A

0.5nm

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9
Q

what is the magnification of a TEM?

A

x1,000,000

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10
Q

what are the strengths of TEMs?

A
  • good resolution
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11
Q

what are the weaknesses of TEMs?

A
  • black and white image
  • 2D image
  • specimens must be dead
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12
Q

what do TEMs allow us to see?

A

small organelles

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13
Q

how do scanning electron microscopes work?

A

electron beam is scanned across the specimen surface and electrons bounce off, gathering in a cathode ray tube

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14
Q

what is the resolution of SEMs?

A

2nm

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15
Q

what is the magnification of SEMs?

A

x500,000

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16
Q

what are the strengths of SEMs?

A
  • 3D image
17
Q

what are the weaknesses of SEMs?

A
  • black and white image
  • specimen must be dead
18
Q

what is the magnification calculation?

A

mag = image / actual

19
Q

what does magnification mean?

A

amount of times the image has been expanded than the object

20
Q

what does resolution mean?

A

the ability to distinguish between two objects

21
Q

which lens is the objective?

A

near to specimen

22
Q

which lens is the eyepiece?

A

used to view specimen

23
Q

why are there two lenses on a microscope?

A
  • improves magnification
  • reduces chromatic aberration (diff colours travelling at diff speeds)
24
Q

why is resolution limited for optical microscopes?

A

light has a larger wavelength

25
Q

what is a dry mount?

A

a solid specimen viewed whole or sectioned on a slide under a cover slip

26
Q

what is a wet mount?

A

specimen suspended in liquid with a cover slip placed at an angle

27
Q

how is a squash slide prepared?

A
  • wet mount prepared
  • lens tissue used to press down cover slip
  • used for soft samples
28
Q

how is a smear side prepared?

A
  • edge of slide used to smear a sample to create a thin coating
  • cover slip over top
29
Q

why should specimens on a slide be thin?

A

avoid air bubbles

30
Q

why is a stain sometimes used?

A

increase contrast to improve visibility

31
Q

what is differential staining?

A

distinguishes between two organisms/organelles
- positive dye attracts negative cytoplasm materials

32
Q

what is a gram stain?

A
  • separates pos/neg bacteria
  • crystal violet is applied to slide
  • iodine applied to fix dye
  • washed with alcohol
33
Q

what is the acid fast technique?

A
  • differentiates mycobacterium
  • lipid solvent carries a dye into cells
  • mycobacterium not affected by acid alcohol cell wash absorbs dye
34
Q

how are mm converted to micrometres?

A

x1000

35
Q

how are micrometres converted to nm?

A

x1000

36
Q

how do you identify what is stained when using crystal violet and methylene blue?

A

negative organelles attract positive stain

37
Q

how do you identify what is stained when using nigrosin or methylene blue?

A

positive organelles attract negative stain

38
Q

how does a laser scanning confocal microscope work?

A
  • laser beam focuses on a small area on a sample surface
  • fluorophores in sample emit photons
  • photomultiplier tube amplifies signal onto a detector
  • image is produced in pixels
39
Q

how is the actual length of an image calculated using a stage micrometer?

A
  • line up eyepiece graticule with stage micrometer
  • count how many graticule divisions are in 100 micrometres
  • number of divisions / 100 = 1 division

Biology 2.1.1: Cell Structure (4 decks)

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