THEORIES
Protein – lipid sandwich mode
3 LAYERS:
- Dark outer layers (x2) on top and bottom = burger buns
- Lighter inner layer (x1) in the middle = filling
FAULTS WITH THIS THEORY:
- 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
IMPROVEMENTS
- 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
- Specific membrane proteins were labelled in either type of cell
- Mouse is labelled dark
- Human is labelled light
- 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
- 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