Cell fractionation

• Why is cell fractionated used?

  • To isolate different organelles
• What are the 2 steps of cell fractionation

  • First homogenisation
  • Second ultracentrifugation
• What are the conditions of ultracentrifugation?

  • Cold, to reduce enzyme activity
  • Isotonic, so the water potential is equal to prevent organelles from bursting
  • Buffered, to prevent damage to organelles
• What happens in step 1, homogenisation?

  • The sample is blended to break up the cell and release the organelles, then filtered to remove large cell debris
• What happens in step 2, ultracentrifugation?

  • The filtrate is spun at increasing speeds and organelles separate according to their densities
  • The dense organelles settle at the bottom and are filtrate off
• What is the solution called in cell fractionation?

  • The supernatant
• What is the order of densities from most dense to least dense?

  • Nuclei (would only take 1 spin)
  • Chloroplasts (if using plants)
  • Mitochondria
  • Lysosomes
  • Endoplasmic reticulum
  • Ribosome