1. 3-8 Movement across the membrane

2. Diffusion
Molecules spread out, or move from areas where there are many too areas where there are few.
Why does it happen?

3. 1) constant motion
2) spread out until evenly distributed
In cells
1) Oxygen needed for respiration enters cell by diffusion.
2) Carbon dioxide leaves by this process.

4. Concentration
Number of particles of that substance in a specific volume.
When there is a difference in the concentration of a substance of a substance between two areas, diffusion occurs.

5. Concentration and Diffusion

6. Diffusion in cells Materials move in and out of cells.
Pass through gaps in cell membrane.
Diffusion is a form of passive transport, materials move without using cell’s energy.
How well a substance diffuses across a cell membrane depends on how well the substance dissolves in the lipids.

7. Osmosis
The diffusion of water through a membrane.

8. Some transport requires energy
Active transport is the process of using energy to move materials through a membrane.
Removal of excess salt from the body.
Marine Iguana

9. Endocytosis and Exocytosis
Move in or rid the cells of large materials.
A pocket is used to move the material in or out of the cell.

10. Cell size affects transport
Read page 62-63
Be ready to discuss.

11. Page 63 # 1-6