1. 7-3 Movement through the Membrane
The cell membrane is semipermeable
- only certain molecules can get through
Passive transport: no energy required
1. Diffusion: the movement of molecules from a region of high concentration to a region of low concentration

2. - continues until equilibrium is reached (equal concentrations on both sides of membrane)

3. - temperature affects diffusion:
higher = faster
- size of particles affects diffusion:
smaller = faster

4. 2. Osmosis: the diffusion of water. across a membrane from high water
2. Osmosis: the diffusion of water across a membrane from high water concentration to low water concentration
97% water
100% water
Which way will the water move?

5. 97% water
90% water
Which way will the water move?

6. This solution is hypertonic - water diffuses out of the cell
This solution is hypotonic
- water diffuses
into the cell

7. This solution is isotonic - no net change
95% water
This solution is isotonic
- no net change

8. 3. Facilitated diffusion: uses protein channels to move molecules from high concentration to low concentration
Active Transport: energy required
1. Carrier proteins may act as pumps
-example: sodium-potassium pump
a. Cells continually pump potassium ions into the cell, and sodium ions out

9. Important for muscle contraction and nerve impulse transmissionK+

10. 2. Endocytosis: materials move into cell

11. a. Pinocytosis: membrane encloses
a. Pinocytosis: membrane encloses a fluid droplet and brings it inside the cell
b. Phagocytosis: membrane encloses a large particle and brings it inside the cell

12. 3. Exocytosis: materials move outside the cell
- wastes and cell products may leave the cell this way

13. 7-4 The Diversity of Cellular Life
Unicellular organisms
a cell is the entire organism
Do everything you would expect from a living things
prokaryotic include bacteria
eukaryotic include algae

14. Multicellular Organisms that contain many cells
Cells are specialized to perform particular functions within the organism
Levels of organization
Cells
Tissues
Organs
Organ systems