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Summary AQA ALEVEL BIOLOGY - CELLS - cell centrifugation
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5/10122cell fractionation and ultracentrifugation
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on
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cell fractionation:
Process where cells are broken
up and the different organelles they contain are
separated out
sample must be:
Chydrolytic
cold
He to reduce lytic enzyme activity some membranes on
organelles are broken, e.g lysosomes digestive enzymes released digest other substances.
- - -
pl buffered to
prevent damage to organelles Buffers Stop pl from changing by becoming acidic or alkaline. Any
change in
pH could alter the structure of the structure of the organelles or affect functioning of enzymes
-
Isotonic to water in cell outside cell.
prevent osmotic
lysis keeps cone
of the same
of Of the same water potential as the tissue to
prevent organelles bursting shrinking as a result
of smoke gain/lossather.
-
-
or
Two stages Homogenisation and
ultrasentrifugation/differential centrifugation
-
Homogenisation
Breaks
open cell membrane/cell wall of sample
cells are broken
up by a
homogeniser (blender).
↳ this releases the
organelles from the cell.
The resultant homogenate,
fluid, known as the is then filtered to remove
any complete cells and large pieces of debris.
Differential centrifugation
process where the
fragments in the
filtered homogenate are
separated in a machine called a
centrifuge.
the centrifuge spins tubes of homogenate at very high speed in order to create a
centrifugal force.
Because all the
organelles have different densities, spinning the
sample in a centrifuge allows us to
separate out the
organelles
The less dense to separate it from
the
organize, the faster the
centrifuge must spin in order the rest of the sample.
Before the 'solution'
we
spin, must be
filtered
Filtration removes cellular debris
-type of lysosome
cempyan
(spins out at lower speed
most dense Nuclei
Mitochondria
(chloroprasts
Endoplasmic reticulum /golgi
Y
least dense Ribosomes
ospins out at
higher speed)
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