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.
what is the 3rd step to ultracentrifugation ?
This process is repeated at higher and higher speeds, until all the organelles are separated out . Each time, the pellet at the
bottom of the tube is made up of lighter and lighter organelles.
list the order (heaviest to lightest) of subcellular structures in an animal cell ?
nuclei, mitochondria, lysosomes , endoplasmic reticulum, and ribosomes
list the order (heaviest to lightest ) of subcellular structure in a plant cell?
nuclei, chlotoplasts ,mitochondria, lysosomes , endoplasmic reticulum, and ribosomes
