Cell fractionation

• By which process are large quantities of cell organelles collected?


  Cell fractionation.
• What is cell fractionation?

  The process of breaking up cells to separate out the organelles.
• the tissues to be fractionated are stored in a cold, osmotically balanced buffer, why?


  Cold - reduces enzyme activity, breaking down organelles. Equal water potential, prevents bursting or shrinking due to osmosis. Buffered to prevent pH fluctuations altering organelle and enzyme activity.
• What are the two stages of cell fractionation?


  Homogenisation and ultracentrifugation
• What is homogenisation (during cell fractionation)?


  Breaking up of cells in a blender. This releases the organelles into the homogenate.
• What is homogenate (part of cell fractionation)?


  Fluid containing cell organelles, prior to ultracentrifugation.
• Why is the homogenate filtered prior to ultracentrifugation? (cell fractionation)


  To remove whole cells and large debris.
• How is ultracentrifugation carried out? (cell fractionation)


  The homogenate filtrate is loaded into a centrifuge which spins the solution until the heaviest particles collect at the bottom of the tube. This remaining fluid is collected and spun at a higher speed. This continues collecting progressively lighter material using higher speeds.
• What is the fluid collected from the centrifuge called?


  Supernatant.
• What is the solid left in the centrifuge tube after the supernatant has been removed, called?

  Sediment.