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
