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OCR A level biology > Microscopy > Flashcards

Microscopy Flashcards

1
Q

How is a wet mount prepared?

A

-place a drop of water on a slide -place the specimen on top -carefully tilt and lower a coverslip ensuring no air bubbles are trapped

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2
Q

How can stain be added to a wet mount?

A

-a drop of stain is placed next to one edge of the cover slip -put a bit of paper towel on the opposite side, this will draw the stain across the specimen

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3
Q

Which two types of microscope require stains to be used?

A

Light microscopes and TEMs

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4
Q

i) What is used to stain nucleic acids? ii) What colour are they stained?

A

i) Methylene blue ii) blue

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5
Q

Name two common light microscope stains

A

Methylene blue and Eosin

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6
Q

What does eosin stain?

A

Eosin stains the cytoplasm pink

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7
Q

i) What does Haemotoxylin stain? ii) What colour does it go?

A

i) Nuclei ii) Blue-purple or black

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8
Q

What is toulidine used to stain?

A

Phloem and xylem, phloem is stained red and xylem is stained green-blue

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9
Q

What is used as a stain for TEM images?

A

Heavy metals e.g lead

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10
Q

How do heavy metals act as stains for electron microscopes?

A

the metal ions scatter the electrons which creates contrast

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11
Q

Name 4 different types of microscope

A

-light microscope -laser scanning confocal microscope -transmission electron microscope -scanning electron microscope

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12
Q

What is the maximum magnification of a light microscope?

A

x1500

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13
Q

What is the resolution of a light microscope?

A

200nm (0.2 micrometres)

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14
Q

What is the maximum magnification of a laser scanning confocal microscope?

A

x1500

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15
Q

What is the resolution of a laser scanning confocal microscope?

A

200nm (0.2 micrometres)

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16
Q

What are laser scanning confocal microscopes used for?

A

Looking at thick specimens at different depths

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17
Q

How does a TEM work?

A

-an electron beam passes through a very thin sample -the denser parts of the specimen absorb more electrons, making it appear darker and providing contrast

18
Q

What is the max. magnification of a TEM?

A

x500,000

19
Q

What is the max resolution of a TEM?

A

0.5nm

20
Q

How does a SEM work?

A

-a beam of electrons are moved across the specimen -electrons are knocked off the specimen -these electrons are gathered in a cathode ray tube to form an image -the image produced is of the surface of the specimen

21
Q

What is the max. magnification of a SEM?

A

x100,000

22
Q

What is the max resolution of a SEM?

A

3-10 nm

23
Q

What does SEM stand for?

A

Scanning electron microscope

24
Q

What does TEM stand for?

A

Transmission electron microscope

25
Q

Define magnification

A

the number of times greater an image is than the object

26
Q

Define resolution

A

the ability to distinguish two separate points as distinct from each other

27
Q

How is magnification calculated?

A

Image size/ actual size

28
Q

How is overall magnification calculated?

A

objective lens x eyepiece lens

29
Q

How do you convert from 1mm to nm?

A

x106

30
Q

How do you convert from nm to µm?

A

x1000

31
Q

How many µm are there in 1mm?

A

1000

32
Q

What colour is the background of an SEM image?

A

Black

33
Q

Are light microscope images 2D?

A

Yes

34
Q

Are TEM images 3D?

A

No they are always 2D

35
Q

Are SEM images 2D?

A

Yes, however they can be processed by a computer to give a 3D image

36
Q

Are LSCM images 3D?

A

Yes

37
Q

What colour background does a light microscope image have?

A

White

38
Q

Does a TEM image have a black background?

A

No it is white

39
Q

What colour is the background for a LSCM image?

A

Black

40
Q

How does a compound light microscope work?

A
  • There are two lenses, one objective, the other the eyepiece lens - The objective lens magnifies the specimen , the eyepiece lens further magnifies this

OCR A level biology (44 decks)

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