3.1 methods of studying cells

Question 1

What is resolution?

Answer 1

the minimum distance apart that two objects can be in order for them to appear separate.
The resolving power depends on the wavelength of the form of radiation used.

Question 2

Why are electron microscopes more resolute than light microscopes?

Answer 2

Electrons have a shorter wavelength than light.

Question 3

What is the equation for magnification?

Answer 3

magnification = image size / actual size

Question 4

What is cell fractionation and why is it necessary?

Answer 4

Cell fractionation is the process where cells are broken up and separated into different organelles.
It is done in order to study individual organelles, and to do this it is necessary to obtain a large number of organelles.

Question 5

What conditions must the tissue be kept in before cell fractionation and why?

Answer 5

COLD- to reduce enzyme activity which might break down organelles
Of the same WATER POTENTIAL as the tissue- to prevent the cell from bursting or shrinking due to osmotic gain or loss of water
BUFFERED- so the PH doesn’t fluctuate, as this could alter organelle structure or affect the functioning of enzymes

Question 6

Describe the process of cell fractionation.

Answer 6

1) cut up a piece of tissue.
2) Break up cells in a homogeniser to release organelles from the cell.
3) filter the homogenate to remove large cells and debris.
4) place filtrate in a centrifuge and spin at a low speed
5) remove the pellet of the heaviest organelles (nuclei)
6) spin the supernatant at a faster speed
7) the next heaviest organelles are forced to the bottom and form a pellet (mitochondria)
8) continue process until you have a pellet of the desired organelle