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A Level Biology > Microscopes > Flashcards

Microscopes Flashcards

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1
Q

Why do we use microscopes?

A

To view cells with an increase in size

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2
Q

What is magnification?

A

The number of times larger than in real life

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3
Q

What is the magnification of a light microscope?

A

2000x

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4
Q

Magnification of an electron microscope?

A

10,000,000x

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5
Q

What is the resolving power?

A

The ability to distinguish between 2 different objects/points

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6
Q

High resolution = what type of wavelength?

A

Short wavelength

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7
Q

What does a high resolution allow us to do?

A

Allows us to see internal structures and organelles e.g. cell membrane, mitochondria

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8
Q

What do all microscopes have?

A

A source of energy
Lenses for focussing
Sensor

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9
Q

What is the wavelength like for an electron microscope (TEM and SEM)?

A

0.004nm

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10
Q

What is the resolution for TEM?

A

0.1nm

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11
Q

What is the resolution for SEM?

A

20nm

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12
Q

What do TEM and SEM use to focus?

A

Magnets

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13
Q

What is the electron micrograph?

A

The image created on a screen or photographic paper

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14
Q

What does the specimen being dehydrated mean? (for a TEM)

A

The specimen is now dead

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15
Q

Why do we cut the specimen into thin slices?

A

We need the electrons and light to pan through

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16
Q

Why do we need to stain the metal ions?

A

Allows us to see them more easily

17
Q

Does TEM pass through the sample or is it directed onto the sample?

A

Passes through the sample

18
Q

Does SEM get passed through the sample or directed onto the sample?

A

Directed onto the sample

19
Q

Is TEM a 2D image or 3D image?

A

2D image

20
Q

Is SEM 3D or a 2D image?

A

3D

21
Q

The darker the parts (TEM)?

A

The thicker the sample

22
Q

Disadvantages of an electron microscope?

A

Expensive
Have to have specialist training to use them
Dead specimens- have to be dehydrated

23
Q

Iodine?

A

Stains carbohydrates in plant and animal specimens brown or blue-black
Stains glycogen red

24
Q

Methylene blue?

A

Stains acidic cell parts (like nucleus) blue. Use on animal, bacteria and blood specimens

25
Q

Eosin Y?

A

Stains alkaline cell parts (like cytoplasm) pink. Use on plants, animals and blood

26
Q

Toluidine blue?

A

Stains acidic cell parts (like nucleus) dark blue. Good to show mitosis in plant cells

27
Q

Crystal violet?

A

Stains bacteria purple

28
Q

Aceto-orcein?

A

Biological stain for chromosomes and connective tissue

29
Q

Method of illuminating sample in light and TEM and SEM?

A

Light- light
Electron- TEM and SEM

30
Q

Method of focussing waves?

A

Light- lenses

TEM and SEM- magnets

31
Q

Can specimen be living?

A

Light- yes
TEM and SEM- no

32
Q

How is the specimen prepared in light microscope?

A

Thin specimen on slide with a cover slip

33
Q

How is the specimen prepared in TEM and SEM?

A

Fixed
Dehydrated
Stained using metal salts
Mounted on a copper grid
Placed in a vacuum

34
Q

What types of stains are used and how do they highlight features?

A

Light- potential staining needed e.g. Acetic orcein
TEM and SEM- specimen are stained with metal salts- this causes electrons to scatter differently, giving contrast

35
Q

Advantage of light microscopes?

A

Cheap

36
Q

Advantage of TEM and SEM?

A

High magnification and resolution

37
Q

Disadvantages of light microscope?

A

Low resolution
Staining needed for non-coloured specimens

38
Q

Disadvantage of SEM?

A

Specimen dead
Large equipment training needed
Vacuum needed
Complex staining process
Electron may destroy specimen

39
Q

Disadvantage of TEM?

A

SAME AS SEM
But also: specimen must be very thin

A Level Biology (30 decks)

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