1. Movement Across Cell Membranes

2. Selectively Permeable Membrane

3. Types of Movement Passive Transport Active Transport Simple Diffusion
Facilitated Diffusion
Osmosis
Active Transport

4. Diffusion
The tendency of particles to move from an area of [high] to an area of [lower].

5. Diffusion Occurs via passive transport.
Energy is not required.
Particles move along [gradient].
Particles reach a dynamic equilibrium.

6. Simple Diffusion Diffusion of molecules across the membrane:
Small, lipid-soluble molecules.
Oxygen.
Carbon dioxide.

7. Facilitated Diffusion
Channel proteins form pores that allow specific ions to pass.
Channel proteins form permanent pores. They can have specific diameters and charges that allow only particular ions to pass through.

8. Facilitated Diffusion
Carrier proteins allow specific molecules to pass based on size, shape and charge.
e.g., Amino acids, sugars and small proteins.

9. Osmosis
The diffusion of water across a selectively permeable membrane.
From an area of high [water] to an area of lower [water].

10. Types of Solutions
One solution is always compared to the other solution.
The solution that loses water is hypotonic.
The solution that gains water is hypertonic.
The solutions are isotonic when there is no net movement of water.
e.g., If a cell shrinks…
The inside is hypotonic relative to the outside.
The outside is hypertonic relative to the inside.

11. Types of Solutions

12. Active Transport Energy is required.
Particles move against [gradient].
Movement requires specific carrier proteins.

13. Endocytosis

14. Exocytosis