1. Academic Biology Notes
Diffusion and Osmosis
Academic Biology Notes

2. Cell Boundaries Cell Membrane Provides protection and support
Regulates what goes in and out of the cell
Made of a lipid bi-layer

3. Cell Boundaries Cell Wall Present in Plant cells ONLY
Provides support and protection for the cell
Made of cellulose, a tough carbohydrate fiber

4. Diffusion Solution- a mixture of 2 or more substances
Solute- the substance that is dissolved (ex. Salt)
Concentration- the amount of solute in a solution

5. Diffusion
Diffusion- particles move from an area of high concentration to an area of low concentration. (High  Low)
Equilibrium- Concentration of solute = Concentration of solvent
Diffusion does NOT require energy!

6. Types of Membranes
Permeable- substance is able to diffuse across a membrane easily
Impermeable- substances cannot pass through
Selectively Permeable- some substances can pass across, while others cannot.

7. Osmosis
Osmosis- the diffusion of water through a selectively permeable membrane
Water moves from an area of high water concentration to low water concentration.

8. The Effects of Osmosis on Cells

9. The Effects of Osmosis on Cells
Solution
Animal Cell
Plant Cell
Isotonic
Concentration of solutes is the same inside and outside of the cell
Water goes in and out at an equal rate
Water goes in and out at an equal rate.
Hypertonic
Concentration of solutes is higher outside of the cell.
Water moves out of the cell. The cell shrinks.
Hypotonic
Concentration of solutes is lower outside of the cell.
Water moves into the cell. The cell swells.

10. Facilitated Diffusion
Cell membranes have protein channels that make it easy for certain molecules to pass through the membrane.
Facilitated diffusion helps to diffuse molecules like glucose across the membrane.
Does NOT require energy!

12. Active Transport
Cells must SOMETIMES move materials in the opposite direction.
Done by transport proteins (“pumps”)
Requires energy

14. Types of Active Transport
Endocytosis- the process of taking material into the cell by infoldings, or pockets, of the cell membrane.
1. Phagocytosis- “cell eating”
2. Pinocytosis- “cell drinking”

16. Types of Active Transport
Exocytosis- Cells release large amounts of material from the cell.

17. Why is transport needed?
To bring food and nutrients into the cell
To maintain homeostasis
To bring wastes out of the cell