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bio module 2 > microscopy > Flashcards

microscopy Flashcards

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Biology 101 flashcards
1
Q

cell theory:

A
  • plant and animal tissue composed of cells
  • cells basic unit of all life
  • cells only develop from existing cells
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2
Q

how does light microscopy work?

A
  • 2 lenses - objective lens near specimen and eyepiece lens through which object is viewed
  • bulb beneath sample = illumination
  • opaque specimen illuminated from above for some
  • diff structures absorb diff amounts / wls of light
  • reflected light transmitted to observer via obj + ep lenses
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3
Q

types of sample prep

A
  • dry mount
  • wet mount
  • squash slide
  • smear slide
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4
Q

how to prepare a dry mount?

A

solid specimen viewed whole or sectioned + placed in centre of slide & cover slip placed at 45° over sample

dust, pollen, insect parts (whole)
muscle tissue, plant tissue (sectioned)

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5
Q

“sectioning” definition

A

cutting a specimen into thin slices with a shark blade

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6
Q

how to prepare a wet mount?

A

specimen suspending in liquid eg. H2O or immersion oil, then cover slip placed at 45°

aquatic samples & living organisms (daphnia)

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7
Q

how to prepare squash slide?

A

prep a wet mount then use lens tissue to press down cover slip (ensure cover slip not damaged maybe use 2 slides instead)

soft samples eg. root tip squashes

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8
Q

how to prepare a smear slide?

A

smear sample via edge of slide at 45° = thin, even coating on another slide then place cover slip over sample

blood (can view cells)

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9
Q

why stain samples?

A
  • allows light / electrons to travel through
  • differential staining: helps distinguish between 2 types of organisms / organelles that could otherwise be hard to identify
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10
Q

“magnification” definition

A

how many times larger then image is then the actual size of the object viewed

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11
Q

magnification equation

A

mag = image size / actual object size

M = I / A

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12
Q

“resolution” definition

A

ability to see and distinguish individual objects as separate entities

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13
Q

LM pros:

A
  • inexpensive
  • small and portable
  • simple sample prep
  • sample prep doesn’t distort material
  • doesn’t require vacuum
  • coloured / stained
  • living / dead specimen
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14
Q

LM cons:

A
  • low resolution
  • low magnification
  • possible artefacts
  • bubbles etc in slide prep = ruined
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15
Q

“artefacts” definition

A

structures produced in specimen prep (damage)

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16
Q

what happens in electron microscopy?

A

beam of electrons with wavelength < 1nm illuminate specimen + show more detailed cell ultrastructure

17
Q

how does transmission electron microscopy work?

A

beam of electrons transmitted through + focused = produces image where more dense structures darker bc absorb more electrons

18
Q

how does scanning electron microscopy work?

A

beam of electrons sent across surface of specimen by electromagnetic lenses = reflected electrons hit collecting device = amplified to produce image on photographic plate

19
Q

EM pros:

A
  • higher res
  • higher mag
  • 3D image produced by SEM
20
Q

EM cons:

A
  • expensive
  • large + must be installed
  • complex sample prep
  • sample prep distorts material
  • vacuum required
  • BW images (TEM)
  • only dead specimen
  • artefacts
21
Q

what is laser scanning confocal microscopy?

A

single focused light across specimen labels specimen fluorescent w dye - laser moved = 2D image produced + many climates = 3D image

22
Q

LSCM pros?

A
  • non invasive
  • used on thick specimen
  • used on 3D specimen
23
Q

LSCM cons?

A
  • lights from other parts of specimen can drop res + cause blurring
24
Q

where can LSCM be used?

A
  • eye diseases (cornea scratches)
  • suspected skin cancer
25
Q

positively charged dyes?

A
  • crystal violet (violet blue)
  • methylene blue (dark blue)
26
Q

negative charge dyes?

A
  • nigrosin (red)
  • Congo red (red)
27
Q

Types of differential staining?

A
  • gram stain technique
  • acid-fast technique
28
Q

what is the gram stain technique?

A
  • crystal violet applied to slide specimen + stain fixed w iodine (blue)
  • slide washed w alcohol = gram pos bacteria retain stain
  • dye gram neg bacteria w counter stain eg safranin (red)
29
Q

why do gram neg bacteria lose the stain?

A

thinner cell walls

30
Q

what is the acid-fast technique?

A

used to differentiate mycobacterium from bacteria

  • lipid solvent carries carbolfuchsin dye into cells to be studied
  • cells washed w dilute acid but mycobacterium unaffected = retain stain
31
Q

what is resolution limited by?

A

refraction of light

32
Q

LM : resolving power + magnification

A

res: 200nm
mag: x2000

33
Q

EM : resolving power + magnification

A

res: 0.5nm (TEM) 3-10nm (SEM)
mag: x500,000

34
Q

LSCM resolving power + magnification?

A

res: 200nm
mag: 2000nm

bio module 2 (7 decks)

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