1. Membrane Structure & Function AP Biology Chapter 7

2. Learning Targets – Membrane Structure  I can explain why membranes are selectively permeable.  I can describe the roles of phospholipids, proteins, and carbohydrates in membranes  I can describe the role of cell walls in plant, bacteria and fungal cells.  I can describe what materials move freely across the phospholipid bilayer and what substances need transport proteins to cross the membrane.

3. Cellular membranes are fluid mosaics of lipids and proteins 7.1

4. Glyco- protein Carbohydrate Glycolipid Microfilaments of cytoskeleton EXTRACELLULAR SIDE OF MEMBRANE CYTOPLASMIC SIDE OF MEMBRANE Integral protein Peripheral proteins Cholesterol Fibers of extra- cellular matrix (ECM)

5. Membrane structure results in selective permeability 7.2

6. Selective Permeability  Cell membrane is “picky” about what is allowed to pass  Related to hydrophobic/hydrophilic nature of phospholipids  Transport proteins, carrier proteins, aquaporins assist in movement across membrane

7. Learning Targets – Membrane Function  I can explain how water will move if a cell is placed in an isotonic, hypotonic or hypertonic solution and predict the effect of these different environments on cells with and without cell walls.  I can explain how materials move into and out of cells both passively and actively  I can describe how a concentration gradient represents potential energy.  I can explain how electrochemical gradients are formed and function in cells.  I can describe how endocytosis and exocytosis move large molecules into and out of the cell respectively.

8. Passive transport is diffusion of a substance across a membrane with no energy investment 7.3

9. Passive Transport  Movement of materials across membrane without using energy  With the concentration gradient  3 types 1. Diffusion 2. Osmosis 3. Facilitated diffusion

10. 1. Diffusion  Movement of molecules from high to low concentration  Ex: O 2, CO 2

11. 2. Osmosis  Movement of water across a selectively permeable membrane  Passive transport – high to low concentration, no energy required  3 osmotic environments

12. A. Hypotonic  Higher concentration of water/lower concentration of solute outside the cell  Water moves into the cell  Animal cells – cytolysis  Contractile vacuole (Paramecium)  Plant cells – turgor pressure

13. B. Hypertonic  Lower concentration of water/higher concentration of solute outside of the cell  Water moves into the cell  Animal cells – plasmolysis  Plant cells – plasmolysis

14. C. Isotonic  Concentration of water and solute is equal on both sides of the membrane  No net movement of water (still moves)  Animal cells – normal  Plant cells – flaccid

15. 3. Facilitated Diffusion  Transport proteins open to allow diffusion of molecules too large to fit otherwise 1. Channel proteins  Channel allows molecules to pass 2. Carrier proteins  Change shape to bind and allow molecules to pass

16. Active transport uses energy to move substances against their gradients 7.4

17. Active Transport  Against concentration gradient, therefore requiring energy (ATP)  2 types  Ion pumps  Cotransport

18. Ion Pumps  Example: sodium-potassium pump  Establish gradient across the membrane for neurons to “fire”  ATP energy used to:  move 3 Na + ions out of the cell while simultaneously moving 2 K + ions into the cell  Animation Animation

19. Cotransport  Membrane protein enables the “downhill” diffusion of one molecule to drive the “uphill” transport of another  Sucrose transport in plants Sucrose transport in plants

20. Bulk transport across the plasma membrane occurs by exocytosis and endocytosis 7.5

21. Endocytosis  Bringing materials into cell 1. Receptor- mediated 2. Pinocytosis 3. Phagocytosis  Animation Animation

22. Exocytosis  Secreting materials out of cell  Animation Animation