Module 2 - Methods of studying cells Flashcards
1
Q
A
2
Q
6 marks
Contrast how an optical microscope and a transmission electron microscope work
and contrast the limitations of their use when studying cells.
A
- TEM uses electrons and optical uses light
- TEM allows a greater resolution
- So with TEM smaller organelles can be observed e.g. ribosome
- TEM view only dead specimens and optical can view live specimens
- TEM requires thinner specimens
- TEM requires a more complex/ time consuming preperation
- TEM focuses using magnets and optical uses glass lenses
3
Q
2 marks
The scientists broke open the cells to produce a suspension of cell contents.
Describe how the scientists would remove large organelles from this suspension of cell contents.
A
- Centrifuge at low speeds
- Large/dense organelles removed in first pellet
4
Q
4 maarks
Describe how a sample of chloroplasts could be isolated from leaves
A
- Break open cells/ homogenise and filter
- In cold, isotonic, buffered solution
- Centrifuge and remove nuclei (nucleus removed in first pellet, filter supernatant)
- Centrifuge higher speed, chloroplasts settle out
5
Q
6 marks
Describe and explain how you would use cell fractionation and ultracentrifugation to obtain a sample of nuclei from muscle tissue.
A
- Homogenise to break open cells
- Filter to remove debris
- Cold solution to prevent enzyme activity
- Isotonic solution to prevent osmosis
- Buffered solution to stop enzymes/protein denaturing
- Centrifuge lower speed so nuclei in pellet/move to bottom