METHODS OF STUDYING CELLS

Question 1

What are microscopes

Answer 1

instruments that produce a magnified image of an object

Question 2

What is the material put under a microscope

Answer 2

object

Question 3

What is an ‘object’ in magnification

Answer 3

the material put under a microscope

Question 4

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

Answer 4

image

Question 5

What is an ‘image’ in magnification

Answer 5

the appearance of the material viewed under the microscope

Question 6

What is the magnification of an object

Answer 6

how many times bigger the image is compared to the object

Question 7

How do you calculate magnification

Answer 7

size of image / size of real object

Question 8

How do you calculate the size of the real object

Answer 8

size of image / magnification

Question 9

What is the resolution of a microscope

Answer 9

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

Question 10

What is another word for resolution

Answer 10

resolving power

Question 11

What does resolution/resolving power depend on

Answer 11

the wavelength or form of radiation used

Question 12

What does greater resolution mean for the image

Answer 12

greater clarity

Question 13

What does greater clarity mean

Answer 13

the image produced is clearer and more precise

Question 14

Is the resolution of a microscope limited

Answer 14

yes

Question 15

Does increasing magnification always increase the resolution

Answer 15

no

Question 16

What is cell fractionation

Answer 16

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

Question 17

What needs to occur before cell fractionation can begin

Answer 17

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

Question 18

Why does the solution before cell fractionation need to be cold

Answer 18

to reduce enzyme activity that might break down the organelles

Question 19

Why does the solution before cell fractionation need to be buffered

Answer 19

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

Question 20

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

Answer 20

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

Question 21

How many stages are there in cell fractionation

Answer 21

3

Question 22

What are the 3 stages of cell fractionation in order

Answer 22

1) homogenation
2) filtration
3) ultracentrifugation

Question 23

What happens during homogenation

Answer 23

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

Question 24

What is ultracentrifugation

Answer 24

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

Question 25

What happens in the centrifuge

Answer 25

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

Question 26

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

Answer 26

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

Question 27

What did cell fractionation enable and how

Answer 27

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

Question 28

What speed of centrifugation does nuclei settle at the bottom

Answer 28

1000 revolutions min-1

Question 29

What speed of centrifugation does mitochondria settle at the bottom

Answer 29

3500 revolutions min-1

Question 30

What speed of centrifugation does lysosomes settle at the bottom

Answer 30

16500 revolutions min-1

Question 31

What happens during filtration

Answer 31

homogenised cell solution is feltered through a hauze to seperate any large cell debris of tissue debris