cells Flashcards
cell fractionation
the process where cells are broken up and different organelles are separated out
before cell fractionation
tissue places in cold buffered solution same water potential as tissue
buffered solution tissue placed in feature
cold- less enzyme activity that could break down organelles
same water potential - prevent organelles bursting or shrinking from osmotic gain or loss
buffered - pH does not fluctuate no organelle structure altered
homogenisation
cells broken up by homogeniser releasing organelles
ultracentrifugation
fragments in filtered homogenise separated in centrifuge
ultracentrifugation in animal cells process
filtrate tube placed in centrifuge and spun at slow speed
heaviest organelles forced to bottom forming thin sediment
fluid at top of tube removed leaving sediment
supernatant transferred to another tube and spun in centrifuge at faster speed
next heaviest at bottom
sedimented and separated increasing speed
electron microscope
electron beam short wavelength so microscope resolves objects well
TEM
electron gun w beam of electrons focused onto specimen
limitations of TEM and SEM
no living organisms
no colour
specimen thin to penetrate -
slow and complicated
SEM
beam of electrons into surface of specimen from above
eyepiece graticule
measure size of objects with light microscope
glass disc placed in eyepiece
stage micrometer
slide to calibrate eyepiece gracticule
nuclear enevelope
double membrane surrounding nucleus w ribosomes on surface
nuclear pores
passage of large molecules out of nucleus
necleoplasm
jelly
