Cell fractionation

• Cell fractionation 


  method to separate organelles so you can study them
• 3 steps in cell fractionation are

  1. Homogenisation
  2. Filtration
  3. Ultracentrifugatıon
• what is homogenisation

  Breaking open a cell by breaking the plasma membrane and this releases the organelle into a solution
• How do you do homogenisation.

  By vibrating a cell or grinding them in a blender
• 3 key features of the solution

  1. ice cold
  2. Isotonic
  3. Buffered
• Why is it important that the solution is ice cold

  it reduces the kinetic energy of enzymes reducing enzyme activity ) so they don’t damage organelle
• Why is the solution isotonic

  Same concentration as the chemicals in the cells to prevent damage to the organelles from shrivelling or bursting due to osmosis
• Why is the solution buffered

  It maintains the pH so proteins and enzymes dont denature that are in the organelle
• what is filtration

  The homogenised cell solution is filtered through gauze to remove large cells or tissue debris
• What is ultracentrifugation used for

  Separates particular organelles from the solution of organelles
• How do you do ultracentrifugation

  Pour solution in a tube and place in the centrifuge at a low speed

  The heavier organelle forms a thick sediment called a pellet at the bottom
• What is the solution above a pellet called

  Supernatant
• What do you do after the first spin

  Drain the supernatant and place in a fresh tube and spin in the centrifuge at a higher speed
• What is the order of organelles from heaviest to lightest

  Nucleus , chloroplast , mitochondria , lysosome , endoplasmic reticulum , ribosomes
• What’s standard deviation 


  The measure of the spread of values about the mean
• How is standard deviation plotted in a graph

  As two error bars

  The larger this bar the greater the standard deviation
• What does two standard deviation bars overlapping show

  that we can say that the two means aren’t significantly different