1. Membrane Function

2. Passive Transport Concentration Gradient Concentration Gradient  A difference in concentrations across the plasma membrane

3. Simple Diffusion Particles diffuse through phospholipid bilayer Particles diffuse through phospholipid bilayer

4. Facilitated Diffusion Translocating (Carrier) Proteins Translocating (Carrier) Proteins  Bind particle  Change shape  Force through membrane

5. Facilitated Diffusion Channel Proteins Channel Proteins  Passage through proteins  Gated - open in response to stimulus Membrane proteins exhibit… Membrane proteins exhibit…  Specificity  Saturation  Inhibition

6. Osmosis Diffusion and fac. diffusion of water Diffusion and fac. diffusion of water

7. Osmosis Continues until equilibrium reached Continues until equilibrium reached OR until another force resists osmosis OR until another force resists osmosis  p = Pressure Potential  s = Solute Potential

8. Osmosis Water Potential (  ) Water Potential (  )  Water moves from high  to low   Depends on  s and  p   s = - i C R T Solution  s at 20C Pure Water 1.0M Sucrose 0.2M NaCl Ionization constant (units/molecule) Molar Conc. Pressure Constant (0.083) Temperature (in K; 273 + C) 0 -24.3 -9.7

11. Active Transport Membrane proteins use ATP to increase conc gradient Membrane proteins use ATP to increase conc gradient

12. Active Transport Sodium-Potassium Pump Sodium-Potassium Pump

13. Electrochemical Gradient Difference in charges and concentrations across a membrane Difference in charges and concentrations across a membrane Produced by electrogenic pumps Produced by electrogenic pumps Serves as potential energy that can be tapped later Serves as potential energy that can be tapped later

14. Exocytosis & Endocytosis

15. Transport Review 1. What types of particles have the toughest time getting through a phospholipid bilayer? 2. What similarities exist between transport proteins and enzymes? 3. What’s the difference between carrier proteins and channel proteins? 4. A certain membrane is impermeable to ions and can withstand 2 bars of pressure before rupture. At 27 o C, how high can the salt concentration be inside the cell before rupturing in a distilled water environment?