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Biology > 2. Practical Skills - Microscopy > Flashcards

2. Practical Skills - Microscopy Flashcards

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?

25
Can live specimens be used in electron microscopes?
No - there's a vacuum and stains can be toxic (made of heavy metal)
26
3D image produced in light microscopes?
Yes - in different planes of focus
27
3D image produced in TEMs?
No
28
3D image produced in SEMs?
Yes
29
Vacuum required in light microscopes?
No
30
Vacuum required in electron microscopes?
Yes
31
Artefacts possible in light microscopes?
Yes
32
Artefacts possible in TEMs?
More common
33
Artefacts possible in SEMs?
Yes
34
Can real colour be seen in light microscopes?
Yes
35
Can real colour be seen in electron microscopes?
No
36
TEM
Transmission electron microscope
37
SEM
Scanning electron microscope
38
Step 1 of cell fractionation/centrifugation
Tissue is cut up and kept in a cold, buffered, isotonic solution
39
Why does solution in step 1 of cell fractionation need to be cold?
Reduces enzyme activity to prevent organelle damage
40
Why does solution in step 1 of cell fractionation need to be buffered?
Maintains pH to prevent denaturation of proteins
41
Why does solution in step 1 of cell fractionation need to be isotonic?
Prevents osmotic effects on organelles
42
Step 2 of cell fractionation
Cut-up tissue is further broken up in a homogeniser (a blender)
43
Step 3 of cell fractionation
Homogenised tissue is spun in an ultracentrifuge at a low speed for 10 minutes
44
Why does the homogenised tissue need to be filtered after step 3?
To remove unbroken cells/large debris
45
Supernatant 1 of centrifugation is a result of...
being spun in ultracentrifuge at low speed
46
What is in supernatant 1?
Heavy organelles (e.g. nuclei)
47
Supernatant 2 of centrifugation is a result of...
being spun in ultracentrifuge at medium speed
48
What is in supernatant 2?
Chloroplasts | Mitochondria
49
Supernatant 3 of centrifugation is a result of...
being spun in ultracentrifuge at high speed
50
What is in supernatant 3?
Lightest organelles (e.g. lysosomes)
51
Why is a homogeniser needed in cell fractionation?
To break open cells and release organelles
52
Why is the homogenised tissue spun at low speeds first?
To remove heavy organelles
53
Why is the homogenised tissue spun at higher speeds after the first sediment is removed?
To obtain lighter organelles
54
Which microscopes require a specimen to be very thin?
Light and TEM
55
In which type of microscope is the beam reflected off the specimen?
SEM

Biology (42 decks)

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