Protein – lipid sandwich mode


  • Dark outer layers (x2) on top and bottom = burger buns
  • Lighter inner layer (x1) in the middle = filling



  • Hydrophilic phosphate heads are not in contact with water when they should be, seeing as it is polar.
  • The proteins contains hydrophobic amino acids which is in contact with water when it shouldn’t be, seeing as it is not polar




  • Darker edges should be phosphate heads because they are more electron dense
  • Lighter inside should be fatty acid tails because they are less electron dense


Freeze Fracture

Frozen membranes are fractured then opened up to show a smooth surface but with large proteins (integral / intrinsic/) proteins embedded.



Mouse + Human cells experiment

  1. Specific membrane proteins were labelled in either type of cell
  • Mouse is labelled dark
  • Human is labelled light
  1. The two cells fuse after some time BUT the proteins/labels continue to remain in their individual halves
  • Supports the idea that integral proteins are hard to remove
  1. Temperature was raised to 37 degrees and after waiting for another hour, the proteins intermixed
  • The only way to have mixed is if they diffused therefore the membrane must be fluid