1. Dynamic Cells Chapter 8 p. 288 - 317  Membrane Properties  Transport Across Cell Membranes  Cell Size and Functions

2. Membrane Properties pg. 290 - 296  Membrane Structure  Membrane Function

3. Phospholipid Bilayer pg.290-291 Cell membranes are composed of a phospholipid bilayer 2 layers of phospholipids with embedded proteins

4. Each layer has: ◦ a hydrophilic phosphate end (hydro = water, philic = loving) ◦ and a hydrophobic lipid tail (phobic = fears, repels)

5. Membrane Proteins can be peripheral (on surface) or integral (spans the membrane) pg. 293

6. Fluid Mosaic Model Cell membranes are constantly MOVING and CHANGING. Gives cell flexibility, movement Changes the positions of the proteins embedded in the membrane, changing the “mosaic”

7. 3 Functions of the Cell Membrane pg. 295 1. Barrier – keeps wastes, toxins, etc. out - allows needed substances in 2. Organization – membranes surround and package materials in vessicles i.e. lysosomes, endoplasmic reticulum

8. 3 Functions of the Cell Membrane pg. 295 3. Selective Filter – SEMI-PERMEABLE – only allows certain substances in or out Regulated by particle size and by selective transport by membrane proteins

9. The Plasma Membrane

10. Transport Across Cell Membranes pg. 297 - 307 3 Types 1. Passive Transport - high concentration to low concentration - no energy (ATP) is required - usually gases (CO 2, O 2, water) because they are very small particles

11. 2. Active transport - low concentration to high concentration - energy (ATP) is required - carrier proteins are usually needed as well

12. 3. Endocytosis/exocytosis - Larger particles are involved - The cell membrane is used to create vessicles (endocytosis) or release particles from vessicles (exocytosis)

13. Brownian Motion and Concentration Gradients p. 297-298  Brownian Motion: matter is made up of tiny particles that are in constant motion laser scanparticle movement

14. PASSIVE TRANSPORT Molecules always move 1) randomly 2) from areas of high concentration to areas of low concentration This is called DIFFUSION

15. Concentration Gradient The difference in concentration between the high and low concentration areas. The greater the difference in concentration – the faster the particles move Eventually equilibrium is reached

16. Why does this happen? At high concentrations the molecules ricochet off of each other and move towards the area of low concentration

17. Equilibrium Remember: at equilibrium the particles DO NOT stop moving, they continue to move back and forth across the concentration gradient.

18. Transport Across Cell Membranes pg. 297 - 307 3 Types 1. Passive Transport 2. Active Transport 3. Endocytosis/Exocytosis

19. Passive Transport pg. 297 - 303 NO ENERGY REQUIRED Small molecules move by diffusion (water, oxygen, carbon dioxide) When WATER molecules move by diffusion across a membrane we call it OSMOSIS

20. Tonicity pg. 299 Hypotonic more water than in the cell Hypertonic less water than in the cell Isotonic Same amount of water

21. Should you drink salt water if you are lost at sea??? Potato Experiment

22. Should you drink salt water if you are lost at sea???

23. Red blood cells in an ISOTONIC solution

24. Red blood cells in a HYPOTONIC solution

25. Red blood cells in a HYPERTONIC solution

26. Plasmolysis in Onion cells Observe the tonicity of the onion cells as a hypertonic saline solution is added to the microscope slide – what happens to the cells?

27. Facilitated Transport (also called facilitated diffusion) Another form of passive transport Used for molecules that are too large to cross the membrane by diffusion (i.e. glucose)

28. Facilitated Diffusion p. 303 Carrier proteins bind to larger molecules, and change their shape so molecules can diffuse through. Channel proteins provide water filled pores for charged ions to pass through

29. Transport Across Cell Membranes pg. 297 - 307 3 Types 1. Passive Transport 2. Active Transport 3. Endocytosis/Exocytosis

30. Active Transport pg. 303 - 304 Molecules move against the concentration gradient (low to high) Energy must be provided (even when we are resting, 40% of our energy is spent on active transport!)

31. Active Transport Uses specialized transport proteins and protein pumps

32. Why spend so much energy on active transport? Maintains internal cell environments (i.e. cell’s electrical gradient, roots pull in minerals from soil, filtering blood in your kidneys)

33. Passive and Active Transport Animations http://www.northland.cc.mn.us/biology/Bi ology1111/animations/transport1.html http://www.northland.cc.mn.us/biology/Bi ology1111/animations/transport1.html

37. Endocytosis/Exocytosis For substances the cell needs to take in (endo = in) or expel (exo = out) that are too large for passive or active transport

38. Two Types of Endocytosis 1. phagocytosis (solids) 2. pinocytosis (liquids)

41. Dialysis, Reverse Osmosis and the Transdermal Patch Dialysis http://www.kidneypatientguide.org.uk/site/ HDanim.php http://www.kidneypatientguide.org.uk/site/p danim.php Reverse Osmosis http://www.geafiltration.com/technology/rev erse_osmosis_flash.asp Nicotine patch http://www.nucleusinc.com/animation4.php