2. Passive Transport: Diffusion & Osmosis 3.4
E.Q. What determines the movement of water into or out of a cell?

3. Passive Transport
Movement of molecules across a cell membrane without the use of energy
2 types: 1.) Diffusion
2.) Osmosis

4. Diffusion
Movement of molecules from a region of high concentration to low concentration
Molecules move down a concentration gradient (difference in the concentration of a substance from 1 location to another)
Occurs because molecules constantly move & collide with one another

5. Osmosis
Diffusion of water from an area of high concentration to an area of low concentration
**The movement of water into or out of a cell is dependent on the concentration of solute inside and outside of the cell.

6. REMEMBER:
SALT SUCKS: Salt is a solute so it will draw the water in its direction

7. Isotonic Solution Iso- = same
The concentration of solute is the same inside and outside the cell
Water will move in and out of the cell equally so the cell will not lose or gain water
Cell size remains constant

8. Isotonic Solution

9. Hypertonic Solution Hyper- = high
Solution has a higher solute concentration than the cell
Water will move out of the cell and into the solution (salt sucks)
Cell will shrink & die (cytolysis)

10. Hypertonic Solution

11. Hypotonic Solution Hypo- = low
Solution has a lower solute concentration than the cell
Water will move from the solution into the cell (salt sucks)
Cell will swell & burst (plasmolysis)

12. Hypotonic Solution

13. Facilitated Diffusion
Diffusion of molecules across a membrane through transport proteins
Facilitate = “to make easier”
Ex.: Glucose – diffuses across membrane thru transport proteins without the use of energy

17. Active Transport, Endocytosis,& Exocytosis 3.5

18. Active Transport
Movement of molecules from a region of lower concentration to a region of higher concentration
Uses energy & transport proteins

19. Endocytosis Process of taking materials into a cell by engulfing them
2 types:
1.) phagocytosis: cell membrane engulfs large particles— “cell eating”
2.) pinocytosis: cell membrane engulfs fluid– “cell drinking”

20. Exocytosis
Release of substances from the cell by the fusion of a vesicle with the membrane
Opposite of endocytosis