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Biology > 2. Practical Skills - Microscopy > Flashcards

2. Practical Skills - Microscopy Flashcards

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1
Q

micrometres symbol

A

μm (10^-6)

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2
Q

nanometres symbol

A

nm (10^-9)

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3
Q

SI unit for distance

A

metres (m)

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4
Q

Rules for biological drawings

A
  1. No sketching/overlapping lines/shading
  2. Add labels: drawn with a ruler and label lines don’t cross
  3. Scale and magnification given
  4. Sharp pencil, title, horizontal writing
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5
Q

Define resolution

A

The minimum distance between two objects at which a microscope can distinguish them as separate

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6
Q

Equation linking magnification, size of image and actual size of specimen

A

magnification = size of image/actual size of specimen

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7
Q

Define magnification

A

The number of times larger an image is compared with the real size of the object

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8
Q

Why does the section of a microscope slide sample need to be so thin?

A

So that light can pass through the sample

Ideal thickness: one cell thick

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9
Q

Which fluids are commonly used in microscope slides and why?

A

Stains to observe structures - most structures are transparent. Provides contrast too.

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10
Q

How do you put on the coverslip? Why do you need to be careful?

A

Lower carefully with a mounted needle.

Need to be careful to avoid air bubbles.

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11
Q

What is magnification controlled by?

A

The power of the lenses used

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12
Q

What is resolution controlled by?

A

The wavelength of light or electrons

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13
Q

Waves of what are used in a light microscope?

A

Light

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14
Q

Waves of what are used in transmission electron microscopes and scanning electron microscopes?

A

Electrons

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15
Q

Which has a shorter wavelength: electrons or light?

A

Electrons: electron microscopes therefore have a higher resolution

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16
Q

How is the beam focused in light microscopes?

A

With glass lenses

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17
Q

How is the beam focused in electron microscopes?

A

Electromagnets

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18
Q

Magnification of light microscopes

A

Low (1000x)

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19
Q

Magnification of TEMs

A

Highest

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20
Q

Magnification of SEMs

A

High (300,000x)

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21
Q

Resolution of light microscopes

A

Low (0.2 micrometres)

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22
Q

Resolution of TEMs

A

Highest

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23
Q

Resolution of SEMs

A

High (2nm)

24
Q

Can live specimens be used in light microscopes?

A

Yes

25
Q

Can live specimens be used in electron microscopes?

A

No - there’s a vacuum and stains can be toxic (made of heavy metal)

26
Q

3D image produced in light microscopes?

A

Yes - in different planes of focus

27
Q

3D image produced in TEMs?

A

No

28
Q

3D image produced in SEMs?

A

Yes

29
Q

Vacuum required in light microscopes?

A

No

30
Q

Vacuum required in electron microscopes?

A

Yes

31
Q

Artefacts possible in light microscopes?

A

Yes

32
Q

Artefacts possible in TEMs?

A

More common

33
Q

Artefacts possible in SEMs?

A

Yes

34
Q

Can real colour be seen in light microscopes?

A

Yes

35
Q

Can real colour be seen in electron microscopes?

A

No

36
Q

TEM

A

Transmission electron microscope

37
Q

SEM

A

Scanning electron microscope

38
Q

Step 1 of cell fractionation/centrifugation

A

Tissue is cut up and kept in a cold, buffered, isotonic solution

39
Q

Why does solution in step 1 of cell fractionation need to be cold?

A

Reduces enzyme activity to prevent organelle damage

40
Q

Why does solution in step 1 of cell fractionation need to be buffered?

A

Maintains pH to prevent denaturation of proteins

41
Q

Why does solution in step 1 of cell fractionation need to be isotonic?

A

Prevents osmotic effects on organelles

42
Q

Step 2 of cell fractionation

A

Cut-up tissue is further broken up in a homogeniser (a blender)

43
Q

Step 3 of cell fractionation

A

Homogenised tissue is spun in an ultracentrifuge at a low speed for 10 minutes

44
Q

Why does the homogenised tissue need to be filtered after step 3?

A

To remove unbroken cells/large debris

45
Q

Supernatant 1 of centrifugation is a result of…

A

being spun in ultracentrifuge at low speed

46
Q

What is in supernatant 1?

A

Heavy organelles (e.g. nuclei)

47
Q

Supernatant 2 of centrifugation is a result of…

A

being spun in ultracentrifuge at medium speed

48
Q

What is in supernatant 2?

A

Chloroplasts

Mitochondria

49
Q

Supernatant 3 of centrifugation is a result of…

A

being spun in ultracentrifuge at high speed

50
Q

What is in supernatant 3?

A

Lightest organelles (e.g. lysosomes)

51
Q

Why is a homogeniser needed in cell fractionation?

A

To break open cells and release organelles

52
Q

Why is the homogenised tissue spun at low speeds first?

A

To remove heavy organelles

53
Q

Why is the homogenised tissue spun at higher speeds after the first sediment is removed?

A

To obtain lighter organelles

54
Q

Which microscopes require a specimen to be very thin?

A

Light and TEM

55
Q

In which type of microscope is the beam reflected off the specimen?

A

SEM

Biology (42 decks)

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