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A Level Biology - Cells > Methods Of Studing Cells (Microscopes) > Flashcards

Methods Of Studing Cells (Microscopes) Flashcards

1
Q

Define magnification

A

Tells you how many times bigger the image produced by the microscope is that the real life object

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2
Q

Define resolution

A

The ability to distinguish between two objects that are close together

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3
Q

How to convert millimetres to micrometres (mm - um)

A

x1000

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4
Q

How to convert micro meters into nanometres

A

x1000

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5
Q

Magnification equation

A

Magnification = Size of image / Size of real object
I
A M

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6
Q

What optical microscopes use to form an image

A

Light

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7
Q

What is the maximum resolution of a light microscope

A

0.2 micrometers (um)

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8
Q

What is the maximum magnification of an optical microscope

A

x 1500

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9
Q

What organelles can’t be seen with an optical microscope

A

Ribosomes, endoplasmic reticulum, lysosomes

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10
Q

What do electron microscope is used for an image

A

Electrons

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11
Q

Which has higher resolution TEM or SEM

A

TEM

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12
Q

Which has greater magnification electron or light microscope

A

Electron

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13
Q

What does the images that electron microscopes produce look like

A

Black and white
(Can be coloured by computer) 

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14
Q

What are the two types of electron microscope

A

Transmission electron microscope’s (TEMs)
Scanning electron microscope’s (SEMs)

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15
Q

How does a transmission electron microscope work

A

Use electromagnets to focus a beam of electrons which is transmitted through the specimen

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16
Q

Advantages of TEMs

A

High resolution
Can see internal structures

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17
Q

Disadvantages of TEMs

A

Thin specimens only
Can’t view living organisms - uses vacuum so no water
No coloured image

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18
Q

What is an artefact in microscopy

A

Looks like a real structure but is the result of preserving or staining a specimen

19
Q

What does the image from TEM look like and WHY?

A

Denser parts absorb more electrons- look darker 

20
Q

How does a scanning electron microscope work

A

They scan a beam of electrons across the specimen
The electrons knock off the specimen and collected by cathode to form an image

21
Q

Advantages of SEM

A

Can be used as thick specimens
Produce 3-D image

22
Q

Disadvantages of SEM

A

Lower resolution than TEM
Cannot be used to observe live specimens

23
Q

What are the steps of cell fractioning (3)

A

Homogenisation
Filtration + cold ionic buffer etc
Ultracentrifugation

24
Q

What does Homogenisation mean

A

Breaking up of cells

25
Q

What is done to the sample of the tissue in homogenisation

A

Placed in an cold,isotonic, buffer solution.

26
Q

Why is the solution ice-cold

A

To reduce the activity of enzymes which break down organelles

27
Q

Why is the solution isotonic

A

Same water potential as the cell to prevent osmosis/lysis

28
Q

Why is the solution of buffer

A

To prevent organelle proteins from becoming denatured

29
Q

What is done with the solution once prepared ( homogenisation)+ what does this achieve /do

A

Added to a homogeniser which grinds up the cell
Breaks the plasma membrane releases the organelles into the homogenate ( solution)

30
Q

What is done during filtration

A

The homogenate is filtered through a gauze
separate large debris
organelles passed through

31
Q

What is the pellet

A

The heavy organelles which settle at the bottom forming a thick sediment

32
Q

What happens during ultracentrifugation

A

Put in a tube
Spun in a centrifuge
Supernatant is put in a new tube
spin again
Repeat

33
Q

What is a supernatant

A

The remaining organelles which are suspended in the fluid above the sediment

34
Q

Describe how you’d make a temporary mount of a piece of plant tissue to observe the position of the starch grains in the cell when using an optical microscope

A

Add drop of water to slide
Add thin section of cell onto slide
Stain with iodine
Lower cover slip using mounted needle

35
Q

Order of cell separation in cell fractioning
5 layers

A

1) nuclei
2) mitochondria
3) Lysosomes
4) ERs + Golgi apparatus
5) ribosomes

36
Q

Why do you
A) push
B)not push sideways
On a microscopic slide

A

A- spread tissue
B- avoid cells rolling together

37
Q

Why would an optical microscope not be able to identify an organelle (2 marks)

A

Low resolution
Light has longer wavelength

38
Q

Give an example of why you may not be able to see the structure inside a cell

A

Not stained

39
Q

How can chloroplasts be isolated from leaves

A

Homogenisation and filter leaves
Place in cold, isotonic, buffer solution solution
Spin in centrifuges and remove cell debris
Spin at higher speed and remove chloroplasts

40
Q

Suggest why you cannot see a nucleus in a image
The image is clear and fairly magnified

A

Not stained

41
Q

Benefits of TEMs over SEMs

A

Higher resolution see internal structures

42
Q

Write out unit conversion from mm to nm

A

Look on posit for answer

43
Q

How to use graticule x3

A

Measure using eyepiece
Calibrate eyepiece gratified against stage ruler
Take number of measurements to calculate mean

A Level Biology - Cells (6 decks)

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