3. ULTRACENTRIFUGATION

• Briefly describe ultracentrifugation?

  separating the organelles
• what are you left with AFTER FILTRATION?

  A solution containing a mixture of organelles
• why do you use centrifugation?

  to separate a particular organelle from all the others
• what is step 1 of ultracentrifugation ?

  • the cell fragments are poured into a tube
  • tube put into a centrifuge and spun at a low speed
  • the heaviest organelles (like nuclei) are flung to bottom of tube
  • they form a thick sediment at the bottom- the PELLET
  • The rest of the organelles stay suspended in the SUPERNATANT
• what is the supernatant?

  the fluid above the sediment
• what is a centrifuge?

  a machine that separates material by spinnning
• step 2 of ultracentrifugation?

  • supernatant is drained off, poured into another tube
  • tube is spun in centrifuge at a higher speed
  • The heaviest organelles, this time the mitochondria, form a pellet at the bottom of the tube
  • the supernatant containing the rest of the organelles is drained off and spun in the centrifuge at an even higher speed
• step 3 of ultracentrifugation?

  this process is repeated at higher & higher speeds, until all the organelles are separated out

  each time, the pellet at the bottom of the tube is made up of lighter and lighter organelles