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BIOL 2A cell structure and division > 3. analysis of cell components > Flashcards

3. analysis of cell components Flashcards

1
Q

what is magnification?

A

how much bigger the image is than the specimen

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2
Q

how is magnification calculated

A

magnification = size of image / size of real object

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3
Q

triangle formula for calculating magnification / size of real object (actual)

A

I

AM

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4
Q

what is resolution?

A

how detailed the image is

how well a microscope distinguishes between two points that are close together

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5
Q

what do optical (light) microscopes use to form an image

A

light

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6
Q
  1. what is the maximum resolution of an optical microscope?

2. what can you see and what cant you see?

A
  1. O.2um (micrometres)
  2. can see - nucleus
    can’t see ribosomes, endoplasmic reticulum and lysosomes.
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7
Q

what is the maximum useful magnification of a light microscope

A

x1500

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8
Q

what do electron microscopes use to form an image

A

electrons

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9
Q

what is the maximum resolution of an electron microscope?

A

0.0002 um

higher resolution than optical = more detailed image

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10
Q

what is the maximum useful magnification of an electron microscope

A

x1,500,000

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11
Q

converting units

A

micrometres (um) -> millimeters (mm) / 1000

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12
Q

how do Transmission electron microscopes work (TEM)

A

1, use electromagnets to focus beam of electrons which is then transmitted through specimen
2. denser part of specimen absorbs more electrons which makes them look darker on the image

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13
Q

advantage of TEM

A

give high resolution images

see internal structure of organelles

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14
Q

disadvantage of TEM

A

can only be used on thin specimens

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15
Q

how do Scanning electron microscopes work (SEM)

A
  1. scan a beam of electrons across specimen.

this knocks off electrons from specimen, which are gathered in a cathode ray tube to form an image

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16
Q

advantage of SEM

A

images show surface of specimen and can be 3D

can be used on thick specimen

17
Q

disadvantage of SEM

A

lower resolution images than TEM

18
Q

how to prepare a temporary mount of a specimen on a slide

4 steps

A
  1. pipette a small drop of water onto slide
  2. use tweezers to place thin section of specimen on top of water drop
  3. add drop of stain (highlights objects in a cell)
  4. add cover slip
19
Q

examples of stains used on temporary mounts

eosin makes what show up?

A

cytoplasm

20
Q

examples of stains used on temporary mounts

iodine in potassium iodide solution stains what?

A

starch grains in plant cells

21
Q

why do you have to CAREFULLY tilt and lower cover slip onto specimen/slide

A

avoid air bubbles (obstruct view of specimen)

22
Q

how to separate organelles

A

cell fractionation

  1. homogenisation - break up cells
  2. filtration - getting rid of big bits
  3. ultracentrifugation (separating organelles)
23
Q

cell fractionation

1. homogenisation (break up cells)

A

grind up cells in blende
breaks up plasma membrane and releases organelles into solution
must be kept ice cold to reduce enzyme activity that break down organelles
solution should be isotonic (same conc of chemicals as cells being broke down)
prevents damage of cells through osmosis
buffer solution added to maintain PH

24
Q

cell fractionation

2. filtration (getting rid of big bits)

A

homogenised cell solution filtered through gauze to separate any large cell debris or tissue debris from organelles (organelles much smaller so pass through gauze)

25
Q

cell fractionation

3. ultracentrifugation (separating the organelles)

A
  1. cell fragments poured into tube. tube put in centrifuge which is spun at a low speed. heaviest organelles nuclei form pellet at bottom. rest of the organelles remain suspended in fluid above (the supernatant)
  2. supernatant drained off poured in another tube and spun in centrifuge at a higher speed. heaviest organelles form pellet (this time mitochondria) supernatant drained off and spun again at a higher speed
  3. process repeated at higher and higher speeds until organelles are separated out
26
Q

order of separation in ultracentrifuge

A 
nuclei 
mitochondria 
lysosomes 
endoplasmic reticulum 
ribosomes

BIOL 2A cell structure and division (5 decks)

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