3.1- Methods of studying cells

Question 1

What is the equation for magnification?

Answer 1

Size of image ÷size of real object

Question 2

What is the equation for size of real object?

Answer 2

Size of image÷magnification

Question 3

How do you convert from mm to micrometers?

Answer 3

x1000

Question 4

How do you convert from mm to nanometres?

Answer 4

x1000000

Question 5

How do you convert from micrometers to nanometres?

Answer 5

x1000

Question 6

Define resolution

Answer 6

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

Question 6

What is cell fractionation?

Answer 6

The process whereby cells are broken up and the different organelles they contain are separated out

Question 7

Why is the tissue placed in a cold solution before cell fractionation can begin?

Answer 7

To reduce any enzyme activity that could break down organelles

Question 8

Why is the tissue placed in a buffered solution before cell fractionation can begin?

Answer 8

To reduce any changes in pH that may alter the structure of the organelles or affect the functioning of the enzymes

Question 9

Why is the solution of the same water potential as the tissue?

Answer 9

To prevent organelles bursting or shrinking as a result of osmotic loss or gain

Question 10

Describe the process of homogenisation

Answer 10

Cells are broken up by a homogeniser which releases the organelles from the cell. The homogenate is then filtered to remove any complete cells and large pieces of debris.

Question 11

What is ultracentrifugation?

Answer 11

The process by which the fragments in the filtered homogenate are separated by being spun in a centrifuge.

Question 12

Describe the process of ultracentrifugation

Answer 12

1. The tube of filtrate is placed in the centrifuge and spun at a low speed
2. The heaviest organelles (nuclei) are separated first and form a pellet at the bottom of the tube
3. The supernatant is removed and spun again in a separate tube
4. The next heaviest organelles ( mitochondria) are separated and form a pellet at the bottom of the tube.
5. The process is continued so that at each increase in speed, the next heaviest organelle is separated out.