Cell fractionation is the process of isolating large numbers of individual organelles to study their function.The tissue is placed in cold buffer solution. The buffer solution has the same water potential as the cells so that the cells are not damaged by osmosis.The buffer solution ensures the pH does not change. The buffer solution is cold so the enzymes do not break down the organelles.The two stages of cell fractionation are homogenisation and ultracentrifugation.Homogenisation means the breaking up of cells by a blender, to release the organelles from the cell. The homogenate is then filtered to remove whole cells and large pieces of debris.The filtrate is then separated using ultracentrifugation.