1. Across Biological Membranes

2. Review for Transport 1. What are the two parts of a solution? 2. In cells, what is normally the solvent? 3. How would you describe the activity of solute particles in solutions?

3. Passive Transport Concentration Gradient Concentration Gradient A difference in concentrations across a membrane A difference in concentrations across a membrane

4. Simple Diffusion Particles diffuse through lipid bi-layers to reach equilibrium Particles diffuse through lipid bi-layers to reach equilibrium Mainly small, nonpolar

5. Facilitated Diffusion Membrane proteins carry materials through the lipid bilayer. Membrane proteins carry materials through the lipid bilayer. 1.Particle binds to membrane protein. 2.Membrane protein changes shape. 3.Particle is released on the other side.

6. Channel Proteins Membrane protein opens a passage for materials through the lipid bilayer. Membrane protein opens a passage for materials through the lipid bilayer.

7. Osmosis Diffusion of water Diffusion of water When solute cannot cross membranes to reach equilibrium, the solvent (water) does When solute cannot cross membranes to reach equilibrium, the solvent (water) does Water moves from where it is purest (hi conc.) to where it is least pure (lo conc.) Water moves from where it is purest (hi conc.) to where it is least pure (lo conc.) H2OH2O H2OH2O H2OH2O H2OH2O H2OH2O H2OH2O H2OH2O H2OH2OH2OH2O H2OH2O H2OH2O H2OH2O H2OH2O H2OH2O H2OH2O H2OH2O

9. Transport Review What two things are always true of passive transport? What two things are always true of passive transport? What are the examples of passive transport we discussed? What are the examples of passive transport we discussed? Why shouldn’t we drink salt water? Why shouldn’t we drink salt water? How do we regulate the amount of water (and concentration of solutes) in our bodies? How do we regulate the amount of water (and concentration of solutes) in our bodies?

11. ADP + P Pump Similar to facilitated diffusion except it’s AT Similar to facilitated diffusion except it’s AT ATP

12. Exocytosis Exocytosis Pre-packaged materials are released from the cell. Pre-packaged materials are released from the cell. Active Transport

13. Endocytosis Endocytosis Cells engulf large materials (nutrients, enemies) with cell membrane. Cells engulf large materials (nutrients, enemies) with cell membrane. Active Transport

14. Endocytosis Endocytosis Cells engulf large materials (nutrients, enemies) with cell membrane. Cells engulf large materials (nutrients, enemies) with cell membrane. Active Transport

15. Review Questions 1. What’s the difference between active and passive transport? 2. In what direction will particles always diffuse? 3. What happens to a wall-less cell in a hypotonic solution? 4. Why might a cell want to build up a concentration gradient?