1.3 Analysis of evidence from electron microscopy that led to the proposal of the Davson-Danielli model.
- Sandwich Model, proteins shown on outside of phospholid layer
- Electron micrograph done using a potassium permanganate skin and showed two dark lines with a pale line inbetween
- Danielli showed how he thought protein lined channels passed through the phospholipid bilayer
1.3 Analysis of the falsification of the Davson-Danielli model that led to the Singer-Nicolson model.
Problems with Davison-Danielli Model:
- Proteins would be exposed to hydrophilic surfaces on both sides which is unstable
- Lipid souble substances couldn't pass through
- Proteins were found to vary in size and shape
- Membrane proteins are free to move instead of being fixed in a peripheral layer
- Discovered after Freeze-etching, Protein-extraction and Antibody Tagging disproved the previous model
- Proteins are within the phospholipid bilayer as well as outside, and they are able to move freely. These are integral proteins
1.5 Evidence from Pasteur’s experiments that spontaneous generation of cells and organisms does not now occur on Earth
- Pasteur used swan-necked flasks in his most famous experiment
- He placed samples of broth in the flasks, then melted the glass of the necks and bent it into a variety of shapes
- He then boiled the broth in the flasks to kill any organisms, however left one unboiled as a control
- Organisms appeared in the unboiled broth but not the boiled, even though the broth was in contact with air, no spontaneous generation occured
- Concluded that spontaneous generation of cells ciuldn't occur
2.5 Methods of production of lactose-free milk and its advantages.