WK03 - Cell Fractionation and Ultracentrifugation

• Tissue samples are homogenised to break open cells.
• The tissue sample should be placed into a isotonic solution to prevent osmosis and lysis.
• The tissue sample should be placed into a buffered solution to prevent changes in pH so enzyme activity isn't affected.
• The tissue sample should be placed into a cold solution to reduce enzyme activity so harmful enzymes cannot harm organelles.
• Homogenisation can be done by hand or with an electric blender, but the latter will cause more damage to cell membranes.
• Low g forces separate large particles such as mitochondria and chloroplasts.
• Medium g forces seperate smaller particles like ribosomes and Golgi apparatus.
• The solution is filtered to remove large debris such as the cell wall.
• Denser organelles (e.g. nuclei) will be collected at slower speeds.
• Sediment pellets are formed at the bottom of the homogenate.