1. Membranes

2. The Cell Membrane: Structure
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The Cell Membrane:
Structure
The fluid Mosaic Model: A phospholipid bi-layer with associated proteins.

3. Functions: Boundary of Cell
Transport of materials in and out of the cell
Communication between cell and environment

4. Membrane Phospholipids:
Structure:
Lipids with a phosphate attached to glycerol in place of a fatty acid tail.
Polar (hydrophilic) phosphate “head”, nonpolar (hydrophobic) fatty acid tails. This type of polar/nonpolar molecule is called “amphipathic”.
Spontaneously organizes in the presence of water to form bi-layer
Fluid: phospholipids are constantly moving.

5. Function:
Makes a “selectively permeable” membrane. Only small, non-polar molecules can easily move through the phospholipid bi-layer (Why?)

6. Cholesterol: Structure: Function: steroid lipid
Acts as a “temperature buffer” to help maintain membrane fluidity over a range of temperatures.
Prevents it from freezing and keeps it from scattering at high temps

7. Membrane Proteins: Structure:
Various, depending on the role they play:
Integral proteins: penetrate one or both layers of the bilayer.
Peripheral proteins: associated with the membrane, but don’t penetrate the bilayer.
The polarity of different regions of a membrane protein vary according to the role of that protein.
glycolipid
integral
peripheral

8. Results:
Membrane proteins are mobile in the cell membrane.

9. Functions:

10. Video

11. Any Questions??