1. Cell Membrane/Plasma Membrane
-All cells are contained by the cell membrane that keeps the pieces inside.
- Think of a plastic bag that has tiny holes in it. The bag holds all the cell pieces and fluid inside of the cell and keeps any bad things outside the cell. The tiny holes allows some things to move in and out of the cell.
- allows materials in or out of the cell

2. The Structure of the Cell Membrane
Consists of:
1) Lipid Bilayer- 2 layers of fat tissue
2) Proteins- embedded into membrane
- help move materials across
-The cell membrane is not solid. It is very flexible.
Cell Membranes are:
Selectively Permeable- controls what materials are allowed to pass through

3. CELL MEMBRANE

4. Types of Transport Across Cell Membranes
What ways can the cell membrane control what enters and leaves the cell?

5. Cell Membrane Processes
Diffusion
- movement of materials from high to low
concentration
- diffusion requires no energy. It is a passive process
- continues until equilibrium is reached (molecules are evenly dispersed)

6. Osmosis Diffusion of water across a selectively permeable membrane
Moves from an area of high water concentration (low solute) to an area of low water concentration (high solute).

7. Cells In Equilibrium
Isotonic: When the osmotic pressure of the solution outside the cell is equal to the osmotic pressure inside the cell. Water enters and leaves the cell at the same rate.
10% NaCl
90% Water
Cell
10% NaCl
90% Water
Cell
10% NaCl
90% Water

8. Cells In High Water Solution
More Water enters than leaves. Cells may swell and burst
10% NaCl
90% water
Cell
30% NaCl
70% Water
What is the direction of water movement?

9. Cells in Low Water Solution
More water leaves than enters. Cells will shrink
Think about why drinking salt water makes you thirsty?
40% NaCl
60% Water
Cell
10% NaCl
90% Water
What is the direction of water movement?

10. Osmosis Continued:
- Red blood cells may shrink or swell due to osmosis

11. * Does not require energy!*
Facilitated Diffusion
- use of proteins in the membrane that aid
diffusion
* Does not require energy!*
-An example of a molecule that uses facilitated diffusion to move in and out of the cell membrane is glucose.

12. Active Transport
- using energy to move materials across the
cell membrane.
- used to fight natural diffusion

13. Cell Transport Vocabulary
A. Movement of water from high to low concentration
B. The use of energy to move particles in/out of the cell.
C. Organelles that move materials in/out of the cell
D. Process of moving materials from high to low concentration
E. Moving materials across a membrane without needing energy
F. The use of proteins to move materials in/out of the cell.