1. Membrane Structure and Function Chapter 7

2. Plasma membrane of cell selectively permeable (allows some substances to cross more easily than others) Made mostly of proteins and lipids (phospholipids). Phospholipids and proteins create unique physical environment (fluid mosaic model)

3. Phospholipid

4. Membrane - bilayer - hydrophilic (water loving) heads pointing outwards, hydrophobic (water fearing) tails pointing inwards. Proteins help membrane to stick to water.

6. Fluid because lipids and proteins can move laterally. As temperatures drop, liquid membrane can solidify.

8. Cholesterol found in membrane helps with fluidity of membrane. Membranes need to be fluid to work properly.

10. Two different types of proteins are found in membrane. 1 Peripheral proteins not in membrane, bound to surface of protein. 2 Integral proteins in membrane often spanning entire membrane.

11. http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/M/MembraneProteins.gif

12. Also aids in cell-to-cell recognition (ability of a cell to distinguish one type of neighboring cell from another)

14. Pass through Membrane Easily Some substances move steadily across membrane (sugars, ions, and wastes like CO 2 ) Hydrophobic molecules (i.e. hydrocarbons, CO 2, and O 2 ) can dissolve in lipid bilayer and cross easily.

15. Charged particles and polar molecules have more difficulty passing.

16. Diffusion - tendency for substance to spread out in open area. Move from an area of Most concentrated to Least concentrated.

18. No force acting upon it - substance will tend to move down it’s concentration gradient (passive transport).

20. Diffusion of molecules with limited permeability through lipid bilayer may be assisted by transport proteins.

21. http://library.thinkquest.org/27819/media/protein_channel.gif

22. Difference in concentration - ions move from one area to other. Solution with higher [ ] solutes - hypertonic. (water moves out) Solution with lower [ ] solutes - hypotonic. (water moves in) [ ] equal - isotonic.

23. http://www.biologycorner.com/resources/hypertonic.gif

24. http://www.biologycorner.com/resources/hypotonic.gif

25. Movement of H 2 O across selectively permeable membrane - osmosis.

27. Organism does not have rigid walls must have ability to osmoregulate and maintain internal environment. Allows plant to stand up against gravity (turgid cell); not watered, plant will begin to wilt (flaccid cell).

29. Plant loses enough water, plasma membrane will pull away from cell (plasmolysis).

30. http://faculty.southwest.tn.edu/jiwilliams/plasmolysis.gif

31. facilitated diffusion - diffusion of substance down it’s [ ] gradient with help of transport protein. Some channel proteins (gated channels) open/close depending on presence/absence of physical or chemical stimulus.

32. In this case, the protein actually rotates to dump the materials to the inside of the cell.

33. Active transport- materials need to be moved against [ ] gradient Requires energy of cell to move substances from an area of low [ ] to an area of high [ ] (i.e. sodium- potassium pump in animal cells)

34. http://www.sp.uconn.edu/~terry/images/anim/antiport.gif

35. Sodium-potassium pump actively maintains gradient of sodium (Na + ) and potassium ions (K + ) across membrane. Sodium-potassium pump uses energy of 1 ATP to pump 3 Na + ions out and 2 K + ions in.

37. http://bioweb.wku.edu/courses/Biol131/images/neuronions.GIF

38. Some organisms have proton pumps that actively pump H + out of cell (i.e. plants, bacteria, and fungi)

40. More Active Transport Exocytosis - When membranes meet - fuse - material is let out to outside of cell. Endocytosis - Membrane is inwardly pinched off and vesicle carries material to inside of cell.

41. http://www.kscience.co.uk/as/module1/pictures/endoexo.jpg

42. 1 Phagocytosis (“cell eating”) - cell engulfs particle by extending pseudopodia around it, packaging it in a large vacuole. Contents of vacuole are digested when vacuole fuses with lysosome.

44. 2 Pinocytosis (cell drinking) - cell creates vesicle around droplet of extracellular fluid.

46. 3 Receptor-mediated endocytosis - specific in transported substances. Extracellular materials bind ligands (receptors) - causes vesicle to form. Allows materials to be engulfed in bulk (i.e. cholesterol in humans)