1. Cell Membrane

2. Membrane are NOT static
Membranes are constantly:
Forming
Transforming
Fusing
Breaking Down

3. Photograph of a Cell Membrane
~ 8 nm thick

4. Cell Membrane
The plasma membrane is flexible and allows a unicellular organism to move

5. Role of cell membrane Serves as a protective barrier
Regulates transport (selectively permeable)
Allows cell communication and recognition
Cells have the ability to distinguish one type of neighboring cell from another
This attribute is important in cell sorting and organization into tissues and organs in development

6. Cell Recognition
Ability to distinguish one type of neighboring cell from another
Important in cell sorting and organization into tissues
This is the basis for rejection of foreign cells by immune system (ex. Human blood type)
Cell recognize other cells by keying on surface molecules, often carbohydrates, on the plasma membrane.

7. Role of cell membrane cont.
Bind cells together
Contains the cytoplasm
PROTEINS determine most of the membrane’s specific functions

8. Structure of the Cell Membrane

9. Structure of Cell Membrane

10. Fluid Mosaic Model of Membrane Structure
Individual phospholipids and proteins can move around freely
Mosaic
The pattern produced by the scattered protein molecules when the membrane is viewed from above
Fluidity Animation
:47-1:20 seconds
With narration

11. Lipid Bilayer
Bilayer gives cell membranes a tough, flexible structure that forms a strong barrier between the cell and its surroundings

12. Cholesterol in membranes
Membranes may be composed of up to 25% cholesterol
Helps control cell membranes fluidity
Restricts movement of tails
Cholesterol Animation

13. Glycoproteins Proteins with attached carbohydrate chain
Play an important role:
in cellular recognition
act as receptors for hormones

14. Proteins are critical to membrane function
Proteins in the cell membrane help the cell interact with its environment
Carry nutrients across cell membrane
Receive chemical signals from outside the cell
Act as an enzyme
Anchor the cell in a location