3.1- METHODS OF STUDYING CELLS

Question 1

What are microscopes?

Answer 1

instruments that produce magnified image of object

Question 2

What can act as a simple magnifying glass?

Answer 2

simple convex glass lens

Question 3

How can simple convex glass lenses work more effectively?

Answer 3

when they’re used in pairs in a compound light microscope

Question 4

What sort of wavelength do light rays have?

Answer 4

long wavelength

Question 5

What does light rays having long wavelengths mean?

Answer 5

light microscope can only distinguish between two objects if they’re 0.2μm or further apart

Question 6

How can the limitation of light microscopes only being able to distinguish between two objects if they’re 0.2μm or further apart, be overcome?

Answer 6

by using beams of electrons rather than beams of light

Question 7

What is the wavelength of electrons like in comparison to wavelength of light rays?

Answer 7

shorter wavelength

Question 8

What are electron microscopes able to as electrons have a shorter wavelength?

Answer 8

beam of electrons in electron microscope can distinguish between two objects only 0.1nm apart

Question 9

What is the material that is put under a microscope referred to as?

Answer 9

object

Question 10

What is the appearance of the material when viewed under the microscope referred to as?

Answer 10

image

Question 11

What is the magnification of an object?

Answer 11

how many times bigger the image is when compared to the object

Question 12

magnification equation:

Answer 12

magnification=

size of real objects

Question 13

What is the resolution or resolving power of a microscope?

Answer 13

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

Question 14

What does the resolving power depend on?

Answer 14

wavelength or form of radiation used

Question 15

What is the approximate resolution power in a light microscope?

Answer 15

about 0.2 μm

Question 16

What does a light microscope having a resolving power of 0.2 μm mean?

Answer 16

any two objects which are 0.2 μm or more apart will be seen separately, but any objects closer than 0.2 μm will appear as a single item

Question 17

What does a greater resolution result in?

Answer 17

greater clarity

image produced is clearer and more precise

Question 18

How does increasing the magnification affect the size of the image and resolution?

Answer 18

increases the size of the image, but doesn’t always increase the resolution

Question 19

Does every microscope have a limit of resolution?

Answer 19

yes

Question 20

What will happen beyond the limit of resolution?

Answer 20

increasing the magnification will reveal more detail but beyond this point increasing magnification will not do this
object will appear larger and more blurred

Question 21

What is necessary to study the structure and function of the various organelles?

Answer 21

to obtain large numbers of isolated organelles

Question 22

What is cell fractionation?

Answer 22

process where cells broken up and different organelles they contain separated out

Question 23

What happens before cell fractionation can begin?

Answer 23

tissue placed in cold, buffered solution of same water potential as tissue

Question 24

Why is the solution cold?

Answer 24

reduce enzyme activity that might break down the organelles

Question 25

Why does the solution have the same water potential as the tissue?

Answer 25

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

Question 26

Why is the solution buffered?

Answer 26

so the pH doesn’t fluctuate

any change in pH could alter the structure of organelles or affect functioning of enzymes

Question 27

How many stages are there in cell fractionation?

Answer 27

two

Question 28

What are the two stages in cell fractionation?

Answer 28

homogenation

ultracentrifugation

Question 29

How are cells broken up?

Answer 29

by a homogeniser (blender)

Question 30

What does the homogeniser do?

Answer 30

release organelles from cell

Question 31

What is the resultant fluid from the homogeniser known as?

Answer 31

homogenate

Question 32

What is done with the homogenate?

Answer 32

filtered to remove any complete cells and large pieces of debris

Question 33

What is ultracentrifugation?

Answer 33

process by which fragments in filtered homogenate separated in machine called centrifuge

Question 34

What does the centrifuge do?

Answer 34

spins tubes of homogenate at very high speed in order to create a centrifugal force

Question 35

process of ultracentrifugation of animal cell (1)

Answer 35

tube of filtrate placed in centrifuge and spun at low speed

Question 36

process of ultracentrifugation of animal cell (2)

Answer 36

heaviest organelles, nuclei, forced to bottom of tube, where they form thin sediment/ pellet

Question 37

process of ultracentrifugation of animal cell (3)

Answer 37

fluid at top of tube (supernatant) removed, leaving just sediment of nuclei

Question 38

process of ultracentrifugation of animal cell (4)

Answer 38

supernatant transferred to another tube and spun in centrifuge at faster speed than before

Question 39

process of ultracentrifugation of animal cell (5)

Answer 39

next heaviest organelles, mitochondria. forced to bottom of tube

Question 40

process of ultracentrifugation of animal cell (6)

Answer 40

process continued in this way so that, at each increase in speed, next heaviest organelle sedimented and separated out

Question 41

speed of centrifugation for nuclei?

Answer 41

1000 revolutions per min

Question 42

speed of centrifugation for mitochondria?

Answer 42

35000 revolutions per min

Question 43

speed of centrifugation for lysosomes?

Answer 43

16500 revolutions per min

Question 44

what did the techniques of cell fractionation and ultracentrifugation enable?

Answer 44

considerable advances in biological knowledge

Question 45

What did cell fractionation and ultracentrifugation allow?

Answer 45

detailed study of structure and function of organelles, by showing what isolated components do