2. II. Movement across the Cell Membrane

3. A. Simple Diffusion 1. Movement for high concentration [ ] to low concentration [ ] a. “passive transport” b. no energy needed Diffusion Animation

4. 2. Diffusion across cell membrane a. Cell membrane is the boundary between inside & outside…  separates cell from its environment IN food carbohydrates sugars, proteins amino acids lipids salts, O 2, H 2 O OUT waste ammonia salts CO 2 H2OH2O products cell needs materials in & products or waste out IN OUT

5. 3. Diffusion through phospholipid bilayer a. What molecules can get through directly?  fats & other lipids inside cell outside cell lipid salt aa H2OH2O sugar NH 3 b. What molecules can NOT get through directly? i. polar molecules H2OH2O ii. ions  salts, ammonia iii. large molecules  starches, proteins

6. 4. Channels through cell membrane a. Membrane becomes semi-permeable with protein channels. specific channels allow specific material across cell membrane  Called TRANSPORT or CARRIER PROTEINS inside cell outside cell sugaraa H2OH2O salt NH 3

7. B. Facilitated Diffusion Facilitated Diffusion Animation Facilitated Diffusion Animation 1. Diffusion through protein channels a. channels move specific molecules across cell membrane b. NO energy needed “The Bouncer” open channel = fast transport facilitated = with help high low

8. C. Active Transport “The Doorman” conformational change 1. Cells may need to move molecules against concentration gradient a. shape change transports solute from one side of membrane to other b. protein “pump” c. “costs” energy = ATP ATP low high

9. Active Transport Example: Nerve Impulse 1. Neurons, nerve cells, have a charge, or electrical potential, across their cell membranes. 2. Sodium (Na + ) is on the outside of the cell and Potassium (K + ) is on the inside 3. The neuron is at rest when the inside of the cell is at -70mV 4. An “action potential” occurs when the nerve is stimulated and sodium moves INTO the cell. The positive Na+ moving into the cell turns the inside positive. Facilitated diffusion 5. After the Na+ channels open, K+ channels open and K+ moves OUT of the cell to reset the negative charge inside the cell. Facilitated diffusion The Nerve Impulse 6. Eventually Na+ must move back OUT of the cell and K+ must move back IN against their concentration gradients. This occurs by Active transport. A Na+/K+ pump is used to move these ions back to their original sides of the cell membrane. Neuron: Na+/K+ Pump

10. Na+/K+ pump

11. D. Review of Membrane Transport 1. Passive Transport  Simple diffusion  diffusion of nonpolar, hydrophobic molecules  lipids  High to low concentration gradient  Facilitated transport  diffusion of polar, hydrophilic molecules  through a protein channel  High to low concentration gradient 2. Active transport  diffusion against concentration gradient  Low to high  uses a protein pump  requires ATP ATP

12. Transport summary simple diffusion facilitated diffusion active transport ATP

13. E. Moving large molecules in & out of cell  Large molecules are IMPERMEABLE to the cell membrane (can’t get through)  There is a way… through vesicles & vacuoles 1. Endocytosis (moving in to cell)  phagocytosis = “cellular eating” Phagocytosis Animation Phagocytosis Animation  pinocytosis = “cellular drinking” 2. Exocytosis (moving out of cell) Endo and Exocytosis Animation

14. Endocytosis phagocytosis pinocytosis fuse with lysosome for digestion non-specific process

15. EXOCYTOSIS

16. Cellular Transport Interactive animation http://www.wiley.com/college/boyer/0470003790/animations/ membrane_transport/membrane_transport.htm