1. Cell Membrane Plasma Membrane Phospholipid Bilayer Semipermeable Membrane
Ch. 7

2. Function of the Cell Membrane
MAINTAIN HOMEOSTASIS
(Stable internal environment)

3. The Gatekeeper
Selectively permeable – allows some substances to cross more easily than others
Made mainly of lipids & proteins

4. Fluid Mosaic Model
Membrane is a fluid structure with a “mosaic” of various proteins
Lipids & some Proteins move laterally
Some Proteins are held still by the cytoskeleton

5. Proteins determine function
1. Integral – many (not all) are transmembrane
2. Peripheral – not embedded in bilayer

6. What moves in and out of the Cell Membrane?
Small molecules & ions move in & out at different rates.
Some move easily, some need help from proteins

7. Transport Proteins
Allow substances to pass avoiding contact with the lipid bilayer.
Channel Proteins: act like a tunnel through the membrane. Pg. 131
Carrier Proteins: carry substances & change their shape to accommodate & pass through the membrane.
Specific for the substances it moves

8. Carrier Protein Example
Glucose has a specific carrier protein to help it move across the membrane.
The protein rejects fructose b/c it is specific for Glucose only.
(Ex. On pg. 131)

9. Animation