3.1) Methods of Studying Cells

Question 1

What is magnification?

Answer 1

How many times bigger an image appears compared to the actual size of the object being observed

Question 2

What is magnification?

Answer 2

How many times bigger an image appears compared to the actual size of the object being observed

Question 3

What is the magnification equation?

Answer 3

magnification= image size/ real size

Question 4

What is resolution?

Answer 4

The ability to distinguish two different points in a specimen.

Question 5

What is a light microscope’s resolution limit?

Answer 5

0.2 micrometers

Question 6

Which microscope has the higher resolution: The light microscope or the electron microscope?

Answer 6

The electron microscope

Question 7

Why do electron microscopes have a higher resolution?

Answer 7

Because of the shorter wavelength which allows them to distinguish between objects as close as 0.1 micrometers

Question 8

What happens if we increase the magnification beyond the limit of resolution?

Answer 8

It doesn’t provide clearer images but makes the image larger and more blurry

Question 9

What is cell fractionation?

Answer 9

The process by which cells are broken up and different organelles are separated out

Question 10

What does steps must take place before cell fractionation can occur?

Answer 10

The tissue is cut up and kept in cold, buffered solution at the same water potential as the tissue.

Question 11

Why is the solution before cell fractionation can occur kept cold?

Answer 11

To reduce enzyme activity that might break down organelles.

Question 12

Why is the solution before cell fractionation kept at the same water potential as the tissue?

Answer 12

To prevent organelles from bursting or shrinking

Question 13

Why is the solution before cell fractionation can occur buffered?

Answer 13

To ensure the pH doesn’t fluctuate

Question 14

What could the fluctuation of pH affect in cell fractionation?

Answer 14

It could change the structure of organelles or affect the functioning of enzymes

Question 15

What are the two stages to cell fractionation?

Answer 15

1. Homogenisation
2. Ultracentrifugation

Question 16

What is meant by homogenisation?

Answer 16

The process by which cells are broken up by a homogeniser (blender), which releases organelles from the cell.

Question 17

What is meant by the term homogenate?

Answer 17

It is the resultant fluid which is filtered to remove any complete cells or large pieces of debris.

Question 18

What is meant by ultracentrifugation?

Answer 18

The process by which the fragments in the filtered homgenate are seperated in a centrifuge.

Question 19

What is meant by the term centrifuge?

Answer 19

A machine that spins the tubes of homogenate at very high speeds in order to create a centrifugal force

Question 20

What does steps take place in the process of ultracentriguation?

Answer 20

1. The tube of filtrate is placed in the centrifuge and spun at a slow speed
2. The heaviest organelles (nuclei) are forced at the bottom of the tube where they form a thin sediment or pellet
3. The fluid at the top of the tube (supernatant) is removed, leaving just the sediment of nuclei.
4. The supernatant is transferred to another tube and spun in the centrifuge at a faster speed than before
5. The next heaviest organelles (mitochondria) are forced at the bottom
6. The process is continued this way , so that at each increase in speed, the next heaviest organelle is sedimented and separated out

Question 21

What is the order of the organelles that will be sedimented and separated out during the process of ultracentrifugation?

Answer 21

1. Nuclei
2. Mitochondria
3. Lysosomes

Question 22

What is the speed of centrifugation for nuceli?

Answer 22

1,000 revolutions min ^-1

Question 23

What is the speed of centrifugation for mitochondria?

Answer 23

3,500 revolutions min ^-1

Question 24

What is the speed of centrifugation for lysosomes?

Answer 24

16,500 revolutions min ^-1