Cell Fractionating

Describe and explain how cell fractionation and ultracentrifugation can be used to isolate mitochondria from a suspension of animal cells. The cells are homogenised in a blender to break open the cells. The homogenised extract is filtered to remove debris. The extract is put in a cold, isotonic and buffered solution. The solution is cold to prevent any enzyme activity, Isotonic to maintain the water potential and to prevent any damage cuased from the change in water potential. Buffered solution helps maintain the pH of the solution so the enzymes and organelles are not denatured. The solution is centrifuged at a low speed, the nuclei forms a pellete at the bottom of the test tube. This is removed. The solution is now removed at a higher speed cuasing the mitochondria to form a pellete, this can then be removed. The solution can a centrifuged again at a higher speed if there is a need to obtain the ribosome.