Cell fractionation

• What is homogenisation?


  • Breaking up cells (either by grinding or vibration)
• How is homogenisation done?

  • Live tissue chopped up in ice cold, isotonic, buffer solution
  • Then ground in homogeniser
  • Releases organelles and forms homogenate
• Why is an ice cold, isotonic buffer solution used?

  Ice cold- stops any enzyme activity

  Isotonic- helps prevent damage to organelles by osmosis

  Buffer- maintain pH
• What happens in centrifugation?


  • Homogenate transferred to ultracentrifuge where mixture is spun at different speeds
  • Pellets form
  • Remaining liquid called supernatant
• In what order do the pellets appear?

  • Nucleus
  • Chloroplast (plants)
  • Mitochondria
  • Lysosome
  • Rough endoplasmic reticulum
  • Ribosome