cell fractionation Flashcards
why would a scientist use cell fragmentation ?
you need to separate specific organelles from the rest of the cell to look at it under the microscope
what is the first step of cell fractionation ?
homogenisation
explain homogenisation
breaking up the cells
e.g. by vibrating the cells or by grinding the cells up in a blender
what dies homogenisation do ?
breaks up the plasma
membrane and releases the organelles into solution
what are the conditions of the solution for homogenisation ?
ice cold ,isotonic ,kept in a buffer solution
why does the solution need to be isotonic ?
same concentration as cells being broken down so prevents damage by osmosis
why does the solution need to be with a buffer solution ?
to maintain the pH
why does the soloution need to ice cold ?
to reduce the activity of enzymes that break down the organelles
what is the second step of cell fractionation ?
filtration
what is filtration for in cell fractionation ?
getting rid of the big bits ,sepperating any large tissue
how is filtration done ?
the homogenised cell solution is filtered through a gauze
what is the 3rd stage of fractionation ?
ultracentrifugation
what is ultracentrifugation for ?
separating the organelles
what is the first step to ultracentrifugation ?
The cell fragments are poured into a tube. The tube is put into a centrifuge (a machine that separates material by spinning) and is spun at a low speed. The heaviest organelles, like nuclei, get flung to the bottom of the tube by the centrifuge. They form a thick sediment at the bottom — the pellet. The rest of the organelles stay suspended in the fluid above the sediment — the supernatant.
what is the second step to untracentrifugation ?
The supernatant is drained off, poured into another tube, and spun in the centrifuge at a higher speed. Again, the heaviest organelles form a
pellet at the bottom of the tube. The supernatant containing the rest of the organelles is drained off and spun in the centrifuge at an even higher speed.
