Cell fractionation is a lab technique
which uses a centrifuge
the contents of a cell
, after the cell
has been turned into a cell-free extract
(the contents of the cell after the cell wall
and/or outer cell membrane
s have been removed).
Some or all of the information in this writeup was taken from the science dictionary at http://biotech.icmb.utexas.edu/; I oversaw the development of the dictionary (the website was mothballed in 1998) and believe I wrote the entry this writeup is partly or wholly based upon.