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Flashcards in METHODS OF STUDYING CELLS Deck (31)
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1

What are microscopes

instruments that produce a magnified image of an object

2

What is the material put under a microscope

object

3

What is an 'object' in magnification

the material put under a microscope

4

What is the appearance of the material viewed under the microscope called

image

5

What is an 'image' in magnification

the appearance of the material viewed under the microscope

6

What is the magnification of an object

how many times bigger the image is compared to the object

7

How do you calculate magnification

size of image / size of real object

8

How do you calculate the size of the real object

size of image / magnification

9

What is the resolution of a microscope

the minimum distance apart that two objects can be in order for them to appear as seperate items

10

What is another word for resolution

resolving power

11

What does resolution/resolving power depend on

the wavelength or form of radiation used

12

What does greater resolution mean for the image

greater clarity

13

What does greater clarity mean

the image produced is clearer and more precise

14

Is the resolution of a microscope limited

yes

15

Does increasing magnification always increase the resolution

no

16

What is cell fractionation

the process where cells are broken up and the different organelles they contain are seperated out

17

What needs to occur before cell fractionation can begin

the tissue needs to be placed in a cold, buffered solution of the same water potential as the tissue

18

Why does the solution before cell fractionation need to be cold

to reduce enzyme activity that might break down the organelles

19

Why does the solution before cell fractionation need to be buffered

so the pH does not fluctuate as a change could alter the structure of the organelle or affect the functioning of enzymes

20

Why does the solution before cell fractionation need to be of the same water potential as the tissue

to prevent organelles bursting or shrinking due to osmotic gain or loss of water

21

How many stages are there in cell fractionation

3

22

What are the 3 stages of cell fractionation in order

1) homogenation
2) filtration
3) ultracentrifugation

23

What happens during homogenation

1) cells are broken up by a homogeniser which releases the organelles from the cell
2) the resulting fluid called the homogenate is filtered to remove any complete cells and large pieces of debris

24

What is ultracentrifugation

the process where fragments in the homogenate are seperated in a centrifuge (machine)

25

What happens in the centrifuge

the tubes of homogenate are spun at a high speed to create a centrifugal force

26

What is the process of ultracentrifugation for animal cells (6 steps)

1) tube of filtrate is placed in centrifuge and spun at low speed
2) heaviest organelles (nuclei) are forced to the bottom of the tube where they form a thin sediment/ pellet
3) the fluid at the top of the tube (supernatant) is removed to leave just the nuclei sediment
4) supoernatant is transferred to another tube and spun in the centrifuge at a faster speed
5) the next heaviest organelles (mitochondria) are forced to the bottom of the tube
6) process is continued with an increase of speed each time until all the organelles are sedimented and seperated

27

What did cell fractionation enable and how

detailed study of the structure and function of organelles through showing what isolated components do

28

What speed of centrifugation does nuclei settle at the bottom

1000 revolutions min-1

29

What speed of centrifugation does mitochondria settle at the bottom

3500 revolutions min-1

30

What speed of centrifugation does lysosomes settle at the bottom

16500 revolutions min-1