1. The Plasma Membrane Plasma Membrane Functions
1a. Sometimes called a cell membrane
1b. Functions:
Holds in cells contents
Controls what enters and leaves the cell.

2. The Plasma Membrane Plasma Membrane Functions
1c. Often compared to a country’s borders and laws saying that certain things can or cannot cross.

3. The Plasma Membrane 2. Plasma Membrane Characteristics
2a. Since the membrane allows some substances but not others to pass through we say it is semipermeable.

4. The Plasma Membrane 2. Plasma Membrane Characteristics
2b. It is fluid, meaning that it rearranges itself in response to its environment

5. The Plasma Membrane 3. Plasma Membrane Structure
3a. The plasma membrane is made of two layers of phospholipids called the lipid bilayer

6. The Plasma Membrane 3. Plasma Membrane Structure
3b. The middle of the membrane is nonpolar, so many types of polar molecules can’t get through.

7. The Plasma Membrane 3. Plasma Membrane Structure
3c. Most of the molecules a cell needs are polar, the plasma membrane has protein channels.
3d. These allow certain molecules to enter and exit the cell.

8. The Plasma Membrane 3. Plasma Membrane Structure
3e. Since the plasma membrane is fluid, the protein channels can move to the place where they are needed.