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BIOLOGY - CELL STRUCTURE AND DIVISION > MISCROSCOPES > Flashcards

MISCROSCOPES Flashcards

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1
Q

What are the 2 types of microscope

A

optical (light) and transmission

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2
Q

What do optical microscopes use to form an image

A

light

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3
Q

What is the mazimum resolution of an optical microscope

A

0.2 micrometres(um)

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4
Q

What organelle can optical microscopes not view (3 points)

A

ribosomes, endoplasmic reticulum, lysosomes

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5
Q

What organelle can optical microscopes view (2 points)

A

mitochondria (just ) , nucleus

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6
Q

What is the maximum magnification of an optical microscope

A

x 1500

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7
Q

What do electron microscopes use to form an image

A

electrons

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8
Q

Which microscope has a higher resolution

A

electron

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9
Q

What is the maximum resolution of an electron microscope

A

0.0002 micrometres (um)

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10
Q

Which microscope has a higher magnification

A

electron

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11
Q

What is the maximum resolution of an electron microscope

A

x 1,500,000

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12
Q

Why does an electron microscope have a higher resolution

A

electron beam has a very short wavelength

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13
Q

Why does the electron microscope have a higher magnification

A

the electrons are negatively charged so the bean can be focused using electromagnets

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14
Q

What are the 2 advantages of electron microscope over optical

A

1) higher resolution

2) higher magnification

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15
Q

How do you convert from micrometres to millimeters

A

divide by 1000

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16
Q

What has to be created inside the chamber of an electron microscope for it to work effectively and why

A

near-vacuum, because electrons are absorbed/ deflected by the molecules in air

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17
Q

How many types of electron microscope are there

A

2

18
Q

What are the types of electron microscope

A

1) transmission electron microscope (TEM)

2) scanning electron microscope (SEM)

19
Q

What does a transmission electron microscope do to create an image

A

uses a beam of electromagnets that is focused onto the specimen by a condenser electromagnet which is then transmitted through the specimen from below

20
Q

What parts of the specimen appear darker on a transmission electron microscope and why

A

denser parts , because they absorb more electrons

21
Q

Which parts of the specimen appear lighter on a transmission electron microscope and why

A

the less dense parts, because they allow electrons to pass through

22
Q

Where is an image produced on a transmission electron microscope and what can be done to it

A

on a screen, and it can be photographed to produce a photomicrograph

23
Q

What is the resolving power of a transmission electron microscope

A

0.1nm

24
Q

Can the resolving power of a transmission electron microscope always be achieved and what are the 2 reasons for this

A

no

1) difficulties preparing the speciment limit the resolution
2) higher energy electron beam is required which may destroy the specimen

25
Q

How many limitations are there for a transmission electron microscope

A

6

26
Q

What are the limitations for a transmission electron microscope (6 points)

A

1) specimen must be dead because the system requires a vacuum
2) image produced is not in colour
3) difficult staining system required
4) specimen must be extremely thin
5) image may contain artefacts
6) only produced a 2D image

27
Q

What are artefacts

A

things that result from the wat the specimen is prepared

28
Q

What part of the organelle do you see with a transmission electron microscope

A

inside of the cell

29
Q

How do you get a 3D image from a transmission electron microscope

A

taking a series of sections through a specimen and then building up the photomicrographs produced

30
Q

Which electron microscope gives a higher resolution

A

transmission electron microscope

31
Q

What does a scanning electron microscope do to produce an image

A

directs a beam of electrons on to the surface of the specimen from above which knocks off electrons from the speciment , which are then gathered in a cathode ray tube to form an image

32
Q

What part of the organelle do you end up with an image of

A

the surface

33
Q

How do you build up a 3D image from a scanning electron microscope

A

analysis of the pattern of scattered elcrons and secondary electrons produced

34
Q

What is the resolution of a scanning electron microscope

A

20nm

35
Q

What are the advantages of a scanning electron microscope over a transmission electron microscope (2)

A

1) specimen does not need to be as thin

2) image produced is 3D

36
Q

What are the limitations of a scanning electron microscope ( points)

A

1) need near-vacuum conditions
2) image may contain artefacts
3) lower resolution
4) lower magnification

37
Q

Which electron microscope gives a higher magnification

A

transmission electron

38
Q

How many steps are there to prepare a slide for an optical microscope

A

4

39
Q

What are the stages in preparing a slide for an optical microscope

A

1) pipette a small drop of water onto the slide
2) use tweezers to place a thin section of specimen on top of the water droplet
3) add a drop of stain to highlight objects in the cell
4) add cover slip by standing it upright next to the water droplet and slowley tilting it lower

40
Q

Give 2 examples of stain used in slide preperation

A

1) eosin - to make cytoplasm show up

2) iodine in potassium iodide solution - to stain starch grains in plant cells

41
Q

What must you ensure when lowering the cover slip onto the slide in slide preperation and why

A

not to get any air bubbles as they will obstruct your view of the specimen

BIOLOGY - CELL STRUCTURE AND DIVISION (18 decks)

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