1. 4.3: The Plasma Membrane

2. Functions of the Plasma Membrane Allows only certain molecules to enter or leave Separates inside from outside Allows waste to be expelled Interacts with its environment

4. Two Parts of Membrane 1. Membrane Lipids - Phospholipids form a bilayer Heads are in the water, tails are out Sterols - other lipids between the tails that make the membrane more firm, prevent freezing

5. Two Parts of Membrane 2. Membrane Proteins - “Integral proteins” Embedded in the lipid bilayer

6. Uses: To identify the cell type Channels, allow certain substances to enter Docking sites for chemical messengers

7. Fluid Mosaic Model The idea that the membrane behaves like a fluid more than a solid. The proteins can move laterally within the bilayer.