1. Cell Structure and Function 7.2

2. Plasma membrane

3. Plasma Membrane Helps cells maintain homeostasis
Contains cell contents
Selectively permeable- allows nutrients in and waste out
Double layer of phospholipids & proteins

4. Phospholipids Polar- arranged head with 2 tails
Hydrophylic head (likes water)
Hydrophobic tail (doesn’t like water)
The polar heads are toward the water- so water soluble substances are blocked by the inner tails.

5. Movement Across the Plasma Membrane
A few molecules move freely
Water, Carbon dioxide, Ammonia, Oxygen
Carrier proteins transport some molecules
Proteins embedded in lipid bilayer
Fluid mosaic model – describes fluid nature of a lipid bilayer with proteins

7. Let’s Review:
1. Describe how the plasma membrane helps maintain homeostasis in a cell.
Controls the substances that enter and exit the cell
2. Explain how the inside of a cell remains separate from its environment.
The phospholipid bilayer provides a barrier