Cell fractionation

• What is cell fractionation?


  A technique which separates organelles according to their density.It involves bursting the cell surface membrane to release the

  organelles and spinning the cell solution at really high speeds.
• Before cell fractionation happens, tissue is placed

  in a solution that is?

  Cold- to reduce enzyme activity that might break down organelles.

  Same water pot- to prevent them from bursting or shrinking as a result of gain or loss of water.

  Buffered- so that pH doesn't fluctuate and affect enzyme function.
• What is this called?

  Homogenation- cells broken up by homogeniser(blender), releasing organelles from cells
• What happens after homogenation?


  Filtration- the homogenised solution (homogenate) is filtered to remove

  any tissue debris. The organelles are small enough to pass through the

  holes of the filter paper so will be present in the filtrate.
• What is the process of centrifuge like for animal cells?


  Tube of filtrate placed in centrifuge and spun at slow speed

  Heaviest organelles, the nuclei, are forced to the bottom of the tube (form pellet)

  Fluid at the top of the tube (supernatant) is removed.

  Supernatant transferred to another tube and spun in the centrifuge at a faster speed

  Next heaviest organelles, the mitochondria, forced to the bottom of the tube

  Process continued 🡪at each increase in speed the next heaviest organelle is sedimented and separated out