1. Cell Membrane
Living Environment

2. Cell Membrane
Fluid Mosaic Model – It is made up of a double layer of phospholipids containing imbedded proteins.
It controls what can enter and leave the cell.

3. It is a fluid structure…not rigid.
It is a semipermeable or selective membrane. Only certain molecules can pass through. Usually smaller ones can go through.

4. Structure of Cell Membrane

5. Movement Across the Cell Membrane
1. Active Transport
requires energy (ATP)
movement of molecules from an area of low concentration to high concentration
Uses carrier proteins embedded in the cell membrane

6. Active Transport

7. Passive Transport / Diffusion
Requires no energy
Movement of molecules from an area of high concentration to an area of low concentration
Establishes a dynamic equilibrium

8. Diffusion

9. Osmosis Osmosis is the diffusion of water.
Water moves through gaps between the phospholipids.
Concentration of solutes (dissolved particles) inside and outside of cells affects osmosis.

10. Hypertonic Solution
Concentration of solutes in the solution is greater than inside the cell.
Water moves out of cell; cell shrinks.

11. Isotonic Solution
Concentration of solutes is the same in the solution and inside the cell.
No net movement of water.

12. Hypotonic Solution
Concentration of solutes in the solution is less than inside the cell.
Water moves into the cell; cell swells.

13. Osmosis and Solute Concentration

14. Movement of Large Particles
Endocytosis – brings large particles in by forming a sac of membrane around them

15. Movement of Large Particles
Exocytosis – getting rid of materials from a sac at the cell’s surface