1. Movement Across Membranes
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2. Concentration Gradient
When the number of molecules or ions in one region is different than the number in another region.

3. Passive Transport No energy needed
Molecules move from high to low concentration.
Example:
Diffusion
Osmosis
Facilitated Diffusion

4. Diffusion
A substance naturally moves from an area of HIGH concentration to an area of LOW concentration.
Ultimately the substances will be evenly distributed and will reach equilibrium.

5. Osmosis Diffusion of water across a selectively permeable membrane.
Water will move from the solution with the higher water concentration to the solution with the lower water concentration across a selectively permeable membrane.

6. Stop ! QuickReview Solvent – Dissolves a substance. EX. WATER!!!!
Solute – Gets dissolved. EX. Salt & Sugar
Solution- Both Solvent and Solvents EX.Mixture of Salt and Sugar

8. Solute concentration between two area
Hypertonic: HIGHER concentration of solutes
Hypotonic: LOWER concentration of solutes
Isotonic: an EQUAL concentration of solutes

9. Facilitated Diffusion uses built in cell membrane protein channels which “help” substances diffuse.

10. Active Transport
Solutes move from an area of LOW concentration to HIGH concentration.
This requires ENERGY in the form of ATP.
Transport proteins help substances move across the membrane (with energy).
Two major types.

11. Exocytosis
Exocytosis: A vesicle fuses with the plasma membrane and contents are released outside the cell

12. Endocytosis
Endocytosis: Forming a vesicle inward toward the cytoplasm.
Phagocytosis- “cell eating”-whole bacteria
Pinocytosis- “cell drinking”-liquids

13. Membrane Crossing: Overview I