MISCROSCOPES Flashcards Preview

BIOLOGY - CELL STRUCTURE AND DIVISION > MISCROSCOPES > Flashcards

Flashcards in MISCROSCOPES Deck (41)
Loading flashcards...
1

What are the 2 types of microscope

optical (light) and transmission

2

What do optical microscopes use to form an image

light

3

What is the mazimum resolution of an optical microscope

0.2 micrometres(um)

4

What organelle can optical microscopes not view (3 points)

ribosomes, endoplasmic reticulum, lysosomes

5

What organelle can optical microscopes view (2 points)

mitochondria (just ) , nucleus

6

What is the maximum magnification of an optical microscope

x 1500

7

What do electron microscopes use to form an image

electrons

8

Which microscope has a higher resolution

electron

9

What is the maximum resolution of an electron microscope

0.0002 micrometres (um)

10

Which microscope has a higher magnification

electron

11

What is the maximum resolution of an electron microscope

x 1,500,000

12

Why does an electron microscope have a higher resolution

electron beam has a very short wavelength

13

Why does the electron microscope have a higher magnification

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

14

What are the 2 advantages of electron microscope over optical

1) higher resolution
2) higher magnification

15

How do you convert from micrometres to millimeters

divide by 1000

16

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

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

17

How many types of electron microscope are there

2

18

What are the types of electron microscope

1) transmission electron microscope (TEM)
2) scanning electron microscope (SEM)

19

What does a transmission electron microscope do to create an image

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

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

denser parts , because they absorb more electrons

21

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

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

22

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

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

23

What is the resolving power of a transmission electron microscope

0.1nm

24

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

no
1) difficulties preparing the speciment limit the resolution
2) higher energy electron beam is required which may destroy the specimen

25

How many limitations are there for a transmission electron microscope

6

26

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

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

What are artefacts

things that result from the wat the specimen is prepared

28

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

inside of the cell

29

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

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

30

Which electron microscope gives a higher resolution

transmission electron microscope

31

What does a scanning electron microscope do to produce an image

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

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

the surface

33

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

analysis of the pattern of scattered elcrons and secondary electrons produced

34

What is the resolution of a scanning electron microscope

20nm

35

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

1) specimen does not need to be as thin
2) image produced is 3D

36

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

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

37

Which electron microscope gives a higher magnification

transmission electron

38

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

4

39

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

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

Give 2 examples of stain used in slide preperation

1) eosin - to make cytoplasm show up
2) iodine in potassium iodide solution - to stain starch grains in plant cells

41

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

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