Cell Membranes and Transport

1. Cell Membranes and Transport -Pick up your ch. 7 reading guide from the back counter Objectives: -Describe the structure and function of the cell membrane -Describe the 4 types of cell transport Understand how to predict the flow of water in/out of a cell Understand the concept of water potential

2. Today • Have your dividers up for the Cell parts quiz • We will start right at the bell • All you need is something to write with

3. 1 - Review • 4 organic compounds • Carbohydrates • Lipids • Proteins • Nucleic acids

4. 2 - Amphipathic – contains both hydrophobic (non-polar) and hydrophilic regions (polar)

5. Phospholipids

6. 3 - Two problems with the sandwich model Not all membranes looked the same (some were 3-layered, some not) Proteins were amphipathic – hydrophobic regions could not be near water

7. 4 - Fluid mosaic model – proposed by Singer and Nicolson in 1972, proteins imbedded in the membrane (hydrophobic portions of proteins and lipids could be separated from water

8. 5 - Membranes need to be fluid to work properly- if a membrane solidifies, its permeability changes and embedded proteins can stop working

9. Cell Membrane Animation • http://www.susanahalpine.com/anim/Life/memb.htm

10. 6 - Membrane Fluidity • In general, decreasing temperature, slows the phospholipid movement and decreases fluidity • Unsaturated fatty acid tails will slow this process by keeping the phospholipids from packing together

11. Cholesterol – temperature buffer • At lower temps, cholesterol prevents membrane from solidifying • At higher temps, cholesterol restrains phospholipid movement

12. 7 - Types of proteins • Integral – embedded completely or partially into the membrane • Transmembrane – span the entire membrane • Unilateral – do not span the entire membrane • Peripheral – attached to the surface of the membrane

13. 8 - Functions of cell membrane

14. 9 – Cell-to-cell recognition • Examples • Sorting of tissues/organs • Determining self/non-self • 10 • Glycolipids – carbohydrates bonded to fat • Glycoproteins – carbohydrates bonded to protein

15. 11 - Fluid Mosaic Model

16. Tomorrow • We will look at diffusion and transport

17. Today • Complete procedure 2 of the lab • Get data • Begin procedure 3 of the lab • Leave experiment overnight • Clean-up • Rinse and dry all cups and other equipment • Keep rubber bands – don’t throw away • Put all equipment on the back table

18. Clean-up • Dry part B cups • Rinse and dry all materials (sugar makes things sticky) • Save rubber bands please • Put all materials in tub – leave on table

19. Warm-up • Complete procedure 3 of the lab • Collaborate with other groups to get class data • Determine which solution is 1M, .8M, .6M, .4M, .2M, and 0M • Clean-up • Throw away potatoes • Rinse all cups and place on sink upside down • Complete step 1 of procedure 3 • Elodea leaves are on back counter • Look at the 2 slides • Slide 1 – elodea leaf, water • Slide 2 – elodea leaf, sucrose • Whiteboard discussion – instructions on next slide

20. Whiteboard • Diagram what happened in one of your potato cups • Draw a before and after • Include molecules that are involved • Be ready to explain why this happened • Write your predictions for which letter represents each solution of sucrose (1M, .8M, .6M, .4M, .2M, and 0M)

21. Lab questions • Procedure 3 step 2 • How did you determine the molar concentrations? • Describe what was happening in the cup when it gained mass. • Lost mass

22. Procedure 3 Answers • 1M – Red (D) • .8M – Orange (E) • .6M – Pink (A) • .4M – Green (F) • .2M – Blue (B) • 0M – Purple (C)

23. Elodea Cell (substitute for onion cell)

24. Elodea Cell Placed in NaCl

25. Have out your ch. 8 notes

26. Upcoming Dates • Monday – diffusion post-lab, osmosis practice • Tuesday – Diffusion lab discussion, review, quiz 2 – chapter 8 • Wednesday – Review • Thursday – Exam • Friday – start next unit

27. You should be able to • Label a prokaryotic, eukaryotic animal, and eukaryotic plant cell (compare and contrast) • Know the function and structure of all organelles • Label and describe the fluid mosaic model of the plasma membrane • Describe which structures and factors affect membrane fluidity

28. Today • Look at diffusion, osmosis, and how these affect cell size and function • Be able to predict which way molecules will move across a selectively permeable membrane • Know the difference between passive and active transport • Compare endocytosis and exocytosis

29. Plasma membrane – selectively permeable

30. 9 - Membrane proteins • Channel proteins – form a tunnel form molecules to pass through the hydrophobic part of the cell membrane (not specific) • Carrier proteins – change shape to transport specific molecules across

31. 9 - Aquaporins • Channel proteins that allow water pass through the plasma membrane

32. 8 - Dissolvability • Hydrophobic (nonpolar) molecules (smaller hydrocarbons, CO2, and O2) dissolve easily – can pass through membrane • Hydrophilic (polar) molecules (ions, water, glucose, sugars) do not pass easily – will only pass through slowly or not at all, they need help to get across quickly (transport proteins)

33. Sidedness of membranes • Outside of plasma membrane is the same on the surface as the inside of the ER, Golgi, and vesicles

34. 10 - Diffusion • Molecules move randomly, yet population of molecules may move directionally • Diffusion creates a system with more entropy (disorder) • Diffusion is spontaneous since it decreases free energy

35. http://www.biosci.ohiou.edu/introbioslab/Bios170/diffusion/Diffusion.htmlhttp://www.biosci.ohiou.edu/introbioslab/Bios170/diffusion/Diffusion.html • http://lessons.harveyproject.org/development/general/diffusion/diffnomemb/diffnomemb.html

36. Fig. 8.10

37. 14 &15 - Types of Transport • Passive – no ATP required, moves from H to L concentration • Diffusion (CO2, O2) • Facilitated diffusion – uses help of transport proteins (water, polar molecules, ions) • Channel proteins • Aquaporins – H2O • Active – moving molecules against concentration gradient (L to H) (requires energy)

38. Diffusion • Movement of molecules from an area of high to low concentration • Does not require energy • Ex. – Smelling food baking in the kitchen, air freshner

39. 14 - Facilitated Diffusion • Needs the help of proteins • Does not require energy (passive) • Aquaporins – facilitate water to diffuse • Gated protein channels – can open or close, can transport molecules in both directions

40. Facilitated diffusion • http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__how_facilitated_diffusion_works.html

41. Warm-up • Pick up your lab sheet from yesterday • Have out a marker or red pen for grading • Have out ch. 8 reading guide • Schedule • Grade cell quiz • Go over rest of Ch. 8 • Go over Diffusion Lab • Ch. 8 practice • Work on osmosis problems • Ch. 8 Quiz • Homework • Review sheets • Study for Test - Thursday

42. Osmosis animation • http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__how_osmosis_works.html

43. Osmosis

44. 10 & 12 - Osmosis • Hypertonic – higher solute concentration • Hypotonic – lower solute concentration • Isotonic – equal concentrations • Water will move from a hypotonic sol’n to a hypertonic sol’n (Remember – we are thinking in terms of solute) • Solute will move from hyper to hypo (high to low solute concentration)

45. Water (Osmotic) Potential – think in terms of H2O • The potential water has to move • Less negative number as higher potential • Distilled water has the highest potential (zero) • When water has another substance dissolved in it, the water molecules have less potential to move (osmotic potential is negative) • Water always move from less negative to more negative (High concentration of water to Low concentration of water)

46. (High concentration of solute) (Less concentration of solute)

47. 15 &16 - Active Transport • Transport protein pumps a molecule against its concentration gradient • Requires ATP for transport • ATP can transfer a phosphate to the transport protein inducing a conformational change • Na-K pump – uses ATP to pump Na out and K in

49. Na/K Pump • http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__how_the_sodium_potassium_pump_works.html