Cell Fractionation and Ultracentrifugation

• Why is cell fractionation used?


  -To isolate different organelles so they can be studied
• What is the first step in cell fractionation?


  Homogenisation- Grinding the cell to break up the plasma membrane to release and separate the organelles
• What conditions must be met during Homogenisation? (3)


  Cold- to reduce enzyme activity which could damage organelles

  Isotonic- same water potential as solution to stop organelles from shrivelling or bursting

  Buffered- to prevent damage to organelles

  
• What must happen after Homogenisation?


  Filtration must occur to remove large cell debris
• What occurs after filtration?

  Ultracentrifugation

  
• What occurs during ultracentrifugation? (3)


  -The centrifuge spins at a high speed, causing pellets of the most dense organelle to form at the bottom of the tube

  -The process repeats at increasingly faster speeds, removing the supernant each time (the liquid) leaving behind the pellet (organelle)

  -The supernant is the spun again, and the process is repeated

  
• What is the order of density of organelles and an acronym to remember it?

  Nuclei New

  Chloroplasts Cars

  Mitochondria Make

  Lysosomes Loud

  ER Engine

  Ribosomes Revs