cell 
Spin 
at 
low 
speed 
and 
force 
Various 
organelles 
Spin 
at 
higher 
speed 
and 
force 
Pellets, 
of nuclei 
d. 
Spin 
e. 
S' v 
at 
— "'x 
highest 
$ 6 ; 
•■0 
07 : 
speed 
and 
force 
T 
— Ly soso me 
M 
— Mitochondrior 
1 
How a centrifuge is used to isolate 
cell components. To separate the 
various particles in cells, biochemists': 
begin by placing whole cells in a 
solution and then breaking the cells 
with a pestle or with high-frequency 
sound waves (a). The mixture is then 
filtered to remove unbroken cells. At 
this point, the cell organelles and 
fragments are free-floating (b). As 
the sample is spun in the centrifuge at 
increasingly higher speeds and 
force, the organelles begin to settle 
to the bottom depending on their size 
and density. First to settle out are 
pellets of nuclei (c). At forces greater 
than 1 0,000 times that of gravity, 
pellets of mitochondria and 
lysosomes sink to the bottom (d). 
Finally, at very high speeds and at 
forces 1 00,000 times that of gravity, 
the very lightest particles and 
organelles begin to settle out (e). 
Fragments 
of endoplasmic 
reticulum 
and other 
light particles 
16 
