1. 3.4 Diffusion and Osmosis
KEY CONCEPT Materials move across membranes because of concentration differences.

2. 3.4 Diffusion and Osmosis
Passive transport does not require energy input from a cell.
Molecules can move across the cell membrane through passive transport.
There are two types of passive transport.
diffusion
osmosis

3. 3.4 Diffusion and Osmosis
Diffusion and osmosis are types of passive transport.
Molecules diffuse down a concentration gradient.

4. 3.4 Diffusion and Osmosis
Diffusion and osmosis are types of passive transport.
Osmosis is the diffusion of water molecules across a semipermeable membrane.

6. 3.4 Diffusion and Osmosis
Diffusion and osmosis are types of passive transport.
There are three types of solutions.
hypotonic
isotonic
hypertonic

7. 3.4 Diffusion and Osmosis
Some molecules can only diffuse through transport proteins.
Some molecules cannot easily diffuse across the cell membrane.
Facilitated diffusion is diffusion through transport proteins.

8. Hypotonic Solution
Solution that has less dissolved solutes than the cell.
Instead Water flows from where it is most concentrated
HIGH
Salt would like to flow out of the cell but it cannot get out because of the cell membrane.
Into the cell where there is more salt and less water
LOW
Less salt on outside of cell
LOW
More salt on the inside
HIGH

9. Result of Hypertonic Solution on red blood cells

10. Hypotonic
Isotonic
Hypertonic

12. How Cells Deal With Osmosis
Paramecium have a contractile vacuole to get rid of excess water.

13. The pressure that water exerts against a cell wall.
Turgor Pressure
The pressure that water exerts against a cell wall.

14. When plant cell membranes pull away from the cell wall.
Plasmolysis
When plant cell membranes pull away from the cell wall.

15. Facilitated Diffusion
Molecules that cannot diffuse rapidly through the membrane use facilitated diffusion to get through the membrane with the help of a carrier protein.

16. Carrier Proteins
Carrier Proteins- are found embedded in the membrane that change shape to allow larger molecules to cross.

17. Ion Channels
Open and close to allow ions to flow down their concentration gradients.