Fluid Mosaic Model

Question 1

Evidence for Davson-Danielli Model?

Answer 1

Electron micrograph of membrane appeared to show a three layered structure.
One light layer (phospholipid bilayer) surrounded by two dark layers (protein)

Question 2

Evidence against Davson-Danielli model?

Answer 2

1. Amount and type of membrane proteins vary between cells
2. Unclear how proteins would permit membrane to change shape without breaking bonds
3. Membrane proteins are largely hydrophobic (wouldn’t be in outside)

Question 3

Freeze- fracturing?

Answer 3

Specimen rapidly frozen
Cracked on a plane through the tissue

Question 4

Membrane functions?

Answer 4

1. Compartmentalisation
2. Cell signalling
3. Site if chemical reactions
4. Barrier