1. MEMBRANE STRUCTURE AND FUNCTION CHAPTER 7 PART 2

2. CELL-TO-CELL RECOGNITION Carbohydrates are often used for ID Glycolipids – carbs bound to lipids Glycoproteins – carbs bound to proteins (most) Important for: Cell sorting in embryo Immune responses Blood types

3. MEMBRANE SYNTHESIS Molecules on the inside of the ER end up on the outside of the membrane

4. MEMBRANE PERMEABILITY Moves easily Nonpolar molecules (hydrophobic) Hydrocarbons, CO 2, O 2 Doesn’t move easily Polar molecules (hydrophilic) Glucose, water Charged molecules surrounded by water Ions

5. AQUAPORINS 3 billion water molecules per second single file Without them, H 2 O would diffuse slowly through the membrane

6. DIFFUSION Passive Transport – requires no energy Substances move from high to low concentration Down the concentration gradient

7. OSMOSIS Diffusion of water across a selectively permeable membrane Difference in FREE WATER CONCENTRATION causes it to move

8. OSMOSIS

9. CELLS WITHOUT WALLS Tonicity – ability of cell to gain or lose water Isotonic “iso” = same No NET movement of water No change in cell size

10. CELLS WITHOUT WALLS Hypertonic Hyper = more (solutes) Water moves out Cell will shrink

11. CELLS WITHOUT WALLS Hypotonic Hypo = “less” (solute) Water moves in Cell size increases Cell will swell and burst

12. OSMOREGULATION Organisms that live in hyper or hypo tonic environments have special adaptations Ex: Paramecium contractile vacuole

13. CELLS WITH WALLS Hypotonic – turgid “very firm” Isotonic – flaccid “limp” Hypertonic – plasmolysis Membrane pulls away from wall Plant wilts

14. FACILITATED DIFFUSION Passive transport with the help of proteins Channel proteins Aquaporins Ion Channels Gated channels open in response to a stimulus

15. ACTIVE TRANSPORT Move things against the concentration gradient Uses energy Sodium-potassium pump

16. MEMBRANE POTENTIAL Voltage across the membrane -50 to -200 mV (inside negative) Energy source for all movement Favors cations in, anions out

17. ION DIFFUSION Electrochemical gradient Chemical force – ions concentration gradient Electrical force – membrane potential

18. COTRANSPORT Substance that was pumped across the membrane does work as it comes back Brings another molecule with it

19. BULK TRANSPORT Exocytosis Transport vesicle from Golgi moves along microtubules toward plasma membrane Endocytosis Cell takes in molecules and matter by forming new vesicles Phagocytosis “eating” Pinocytosis “drinking” Receptor-Mediated Endocytosis

20. BULK TRANSPORT Exocytosis Transport vesicle from Golgi moves along microtubules toward plasma membrane Endocytosis

21. BULK TRANSPORT

22. Endocytosis

23. LIGANDS A molecule that binds to a receptor site of another molecule Ex: LDL