Mitosis and Studying Cells

Question 1

How would you cell fractionate?

Answer 1

1. Break cells open using a homogeniser
   — Ensure solution is Isotonic, Buffered and Ice Cold
2. Filter solution to remove cell debris
3. Ultra Centrifugation
   -Spin test tube
   -Heaviest organelles compress into a pellet at the bottom of the test tube
   -Pour off the supernatant into another tube
   -Spin again

Question 2

Why must the solution used in cell fractionation be isotonic?

Answer 2

Prevents osmosis - Organelles don’t change size / structure / burst

Question 3

Why must the solution be kept ice cold?

Answer 3

Prevents any enzyme activity that could harm the cell organelles

Question 4

Why must the solution be buffered?

Answer 4

To prevent any changes in pH form affecting cell organelles

Question 5

What are some benefits of light microscopes?

Answer 5

1. Simple
2. Cheap
3. Colour images

Question 6

What are some drawbacks of using a light microscope?

Answer 6

1. Lower magnification
2. Lower resolution
3. Small organelles cannot be seen

Question 7

What are some benefits of Scanning Electron Microscopes?

Answer 7

1. Much Higher Magnification
2. Much Higher resolution
   - as the wavelength of an electron is much less than that of light
3. Forms 3D images
4. Don’t need to slice a thin section

Question 8

What are some drawbacks of a scanning electron microscope?

Answer 8

1. Lower magnification and resolution than a TEM
2. Internal structures cannot be seen

Question 9

What are some benefits of a Transmission electron microscope?

Answer 9

1. Higher magnification than SEM
2. Higher resolution than SEM
3. Allows for the viewing of Internal Structures

Question 10

What are some drawbacks of a TEM?

Answer 10

1. Can’t look at living cells
2. Specimens need to be in a vacuum
3. Need to use thin slice of specimen
   - can create artefacts within the image
4. Doesn’t form a colour image

Question 11

What is the definition of resolution?

Answer 11

The shortest distance between 2 points that can be seen

Question 12

What is the magnification formula?

Answer 12

Size of image = magnification x real size

Question 13

What happens in interphase?

Answer 13

1. DNA replicates
2. Replicate organelles

Question 14

What happens during prophase?

Answer 14

1. Chromosomes condense (get short and fat)
2. Nuclear membrane breaks down
3. Centrioles move to the poles

Question 15

What happens during metaphase?

Answer 15

1. Double chromosomes link up on the equator
2. Spindle forms
3. Spindle attaches to centromeres

Question 16

What happens during anaphase?

Answer 16

1. Centromeres split
2. Chromatids are pulled to opposite poles

Question 17

What happens during telophase?

Answer 17

1. Nuclear membrane reforms
2. Cytokinesis > Cytoplasm divides

Question 18

What is the definition of mitosis?

Answer 18

Cell division to form 2 genetically identical daughter cells

Question 19

What is the definition of binary fission?

Answer 19

Asexual reproduction of single celled organisms

Question 20

Describe the process of binary fission

Answer 20

1. Circular loop of DNA replicates
2. These move to opposite ends of the cell
3. Plasmids Replicate
4. Cytoplasm divides to form 2 daughter cells
5. Each has a single copy of the circular DNA