CELLS: Analysing Cell Components Flashcards

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1
Q

Magnification

A

How much bigger the image is than the specimen

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2
Q

Resolution

A

How easily a microscope distinguishes between two points that are close together.

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3
Q

What are the two main types of microscope?

A

Optical

Electron

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4
Q

Optical microscope:

  • How does it form an image?
  • Maximum resolution?
  • Maximum useful magnification?
A
  • Forms an image using light
  • Maximum resolution of 0.2 micrometres
  • Max useful magnification = x 1500
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5
Q

Electron microscope:

  • How does it form an image?
  • Maximum resolution?
  • Max useful magnification?
A
  • Uses electrons
  • Higher resolution of about 0.0002 micrometres
  • Max useful magnification x 1500000
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6
Q

What are the 2 types of electron microscopes?

A

Transmission (TEMs)

Scanning (SEMs)

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7
Q

How do TEMs work?

A
  • Electromagnets focus beam of electrons that is transmitted through specimen.
  • Denser parts absorb more = darker image
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8
Q

What is a strength and limitation of TEMs?

A

+ High resolution images, so can see internal structures of organalles

  • Thin specimens needed
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9
Q

How do SEMs work?

A
  • Scan beam of electrons across specimen.
  • Knocks off electrons from specimen, which gather in cathode ray tube to form image
  • Shows surface, 3D images
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10
Q

What is a strength and limitation of SEMs?

A

+ Thick specimens

  • Lower resolution images
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11
Q

How do you convert from micrometres to mm?

A

Divide by 1000

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12
Q

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

A
  1. Pipette small drop of water onto slide
  2. Use tweezers to place thin specimen on top of water
  3. Add a stain
  4. Add cover slip to protect.
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13
Q

How are organelles separated?

A

Using cell fractionation

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14
Q

What are the 3 steps of cell fractionation?

A
  • Homogenisation - break up cells
  • Filtration - removes large pieces
  • Ultracentrifugation - separates organelles
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15
Q

What does homogenisation do?

A

Breaks up plasma membrane

Releases organelles into solution

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16
Q

How might you homogenise cells?

A

Grinding cells in a blender

17
Q

In cell homogenisation, what must the solution be?

A
  • Ice-cold - reduces enzyme activity
  • Isotonic - prevents damage through osmosis
  • Buffered - maintains pH
18
Q

Describe the process of filtration:

A
  • Homogenised cell solution filtered through gauze
  • Separates large cell debris or tissue debris from organelles.
19
Q

Describe the process of ultracentrifugation:

A
  • Cell fragments poured into tubes
  • Tube put in centrifuge + spun at low speed
  • Heaviest organelles gather at bottom + form thick sediment (the pellet)
  • Supernatent drained off into another tube + spun at higher speed
  • Process repeats
20
Q

Pellet

A

Thick sediment at bototm of centrifuge formed from heaviest organelles

21
Q

Supernatent

A

Fluid above pellet in which the lighter organelles are suspended.

22
Q

What organelle is likely to be the first separated out in ultracentrifugation?

A

Nuclei

23
Q

What organelle is likely to be the second separated out in ultracentrifugation?

A

Mitochondria