Why is cell fractionation used?
used to isolate different organelles so that they can be studied
- enables individual organelle structures and functions to be studied
explain why fractionated cells are kept in a cold, buffered, isotonic solution
cold: to reduce the activity of enzymes that break down organelles
buffered: solution has to have a pH buffer to prevent damage to the organelles
isotonic: organelles must be the same water potential as the solution to prevent osmosis
- osmosis could cause the organelles to shrivel or burst
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Why is cell fractionation used?
used to isolate different organelles so that they can be studied
- enables individual organelle structures and functions to be studied
explain why fractionated cells are kept in a cold, buffered, isotonic solution
cold: to reduce the activity of enzymes that break down organelles
buffered: solution has to have a pH buffer to prevent damage to the organelles
isotonic: organelles must be the same water potential as the solution to prevent osmosis
- osmosis could cause the organelles to shrivel or burst
describe what happens during cell fractionation
homogenisation:
1) the cells must be broken open in the cold, buffered, isotonic solution
(can be done using a blender or by crushing them)
filtration
2) solution is filtered through a gauze to remove large cell debris or tissue debris
ultracentrifugation
3) the filtered solution is spun at high speed in a centrifuge
- this separates organelles according to their density
4) this process is repeated several times
- each time you remove the supernatant (the liquid containing all the organelles that have to be separated) and leave behind the pellet (the organelle that has been isolated)
State the order of sedimentation of organelles during differential centrifugation.
most dense to least dense:
1. nucleus
2. mitochondria
3. lysosomes
4. RER
5. plasma membrane
6. SER
7. ribosomes