Why is the cell membrane so important???

1. Why is the cell membrane so important???

3. Names! • Cell membrane • Plasma membrane • Selectively permeable membrane • Semi permeable membrane

4. Functions of the Cell Membrane • Protects the cell • Regulates what goes in and out of cell • Helps to communicate with other cells • Creates attachments between cells • Dynamic! **Maintains HOMEOSTASIS in the cell**

5. Structure of the Cell Membrane • Phospholipid bilayer – double layered sheet • Properties of the lipids determine the properties of the membrane: • Hydrophobic (“water-fearing”) = tails • Hydrophilic (“water-loving”) cluster together = heads Heads DO touch water, tails DO NOT touch water

7. Fluid Mosaic Modeldev. By Singer & Nicolson 1972 • Proteins move within layers of lipids w/iviscous fluid • Transport • Structure • Hydrogen bonds can form between water and phospholipid heads inside and outside of cell

8. Types of Membrane Proteins • Glycoproteins • Receptor proteins • Recognition proteins • Enzymatic proteins • Attachment proteins • Transport proteins *KNOW THE FUNCTIONS! (pg. 84 in textbook)*

9. The more double bonds there are in the tails the more fluid the membrane • Incr. in temp. causes membr. To be more fluid (because mol. Move faster) • Decr. Temp. (mol. Move slower -> less fluid)

12. Selectively Permeable • Some substances can pass, others cannot pass • Most substances can pass • Substances that are too big or charged cannot cross the bilayer • Therefore, cells need different means of TRANSPORT to move these substances into and out of the cell

13. REVIEW

14. (review slide)

15. REVIEW • Head region of the lipid are polar molecules so they are attracted to water • Tails region of the lipid are nonpolar they repel water. • These molecular properties form the separation of inside and outside the cell.

16. Vocabulary Terms • Solution- mixture in which one or more substances are UNIFORMLY distributed in another. “homogenous solution” • Solute- what gets dissolved. • Solvent- what does the dissolving. • Ex. salt water: • salt is solute • water is solvent. • Ex. Ice tea • Mix is solute • Water is solvent

17. Passive Transport • Requires NO energy!! • Movement from a high concentration to a low concentration!

18. Passive Transport • 1. diffusion • 2. osmosis • 3. facilitated diffusion • 4. diffusion through ion channels

19. Diffusion

20. Diffusion • Individual particles continuously move in random directions • Molecules moving from a greater concentration to a lower concentration • Ex: perfume, air freshener • Simple diffusion– substances pass through the membrane with no outside aid • Ex. substances: Oxygen,Carbon Dioxide, water and lipid soluble molecules

21. Diffusion Molecules are in constant motion they will continue to move until equilibrium is reached. Equilibrium ! Outside cell inside cell O2 O2 O2 O2 Diffusion video: http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__how_diffusion_works.html O2 O2 Low Concentration High Concentration

22. Vocabulary • Concentration gradient: difference in concentrations (amount of solute) • Equilibrium: particles/molecules are equal on both sides of membrane

23. More diffusion -> “equilibrium”!!

24. Describe how oxygen and carbon dioxide move into and out of the lungs and extremities. Page 4 molecular workbench “diffusion, osmosis, active transport”

25. Osmosis

26. Osmosis • Diffusion of WATER from a high concentration to a low concentration across the cell membrane • Water moves DOWN its concentration gradient until equilibrium is reached http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__how_osmosis_works.html

27. membrane 6 water sugar solution There are as many water molecules on the right as there are on the left but many of them are attached to sugar molecules and are not free to move.

28. 7 Molecular movement Because there are more freely moving water molecules on the left, more diffuse through the pores of the membrane from left to right than from right to left.

29. Iso – Hyper – Hypotonic Solutions

30. Vocabulary • Isotonic: concentration inside and outside of cell are the same  no net diffusion • Hypertonic: when concentration of solute outside of cell is greater, water moves out of cell (shrink) (High solute, Low water) • Hypotonic: concentration of solute inside of cell is greater, water moves into cell (burst) (Low solute, High water)

31. Osmosis in animal cells 11 so water diffuses into the cell by osmosis There is a greater concentration of free water molecules outside the cell than inside and the cell swells up

32. Where is there more water? Which way will it move? Type of Solution? Out of the cell Into the cell Hypotonic Solution

33. Where is there more water? Which way will it move? Type of Solution? Equal No net movement Isotonic Solution

34. Where is there more water? Which way will it move? Type of Solution? In the cell Out of the cell Hypertonic Solution

35. Plasmolysis

36. Plants! • Plasmolysis = cell shrinks away from cell wall due to water loss ex: drought (low rain fall) causing plants to wilt • Turgid: swollen • Turgor pressure the rigidity of plant cells when they contain enough water so that the cell membrane exerts pressure on the cell wall. • Can tell turgor pressure is low when plant wilts

37. Osmosis: the diffusion of water as seen in class. • Size of a cell membrane can change as the amount of water inside changes in response to external conditions change. Cells surrounded by “salt” water Cells surrounded by “plain water”

38. Facilitated Diffusion

39. Facilitated Diffusion • Uses specific protein pores in the cell membrane to move certain “large” molecules from high concentration to low concentration. • Used for transport of water soluble molecules (hydrophillic). Ex: ions, amino acids (small proteins), and sugars • Carrier Protein- protein recognizes substance->changes shape->delivers substance to inside of the cell • Aquaporins – allow water to cross at a fast rate via faciliated diffusion http://highered.mheducation.com/sites/0072495855/student_view0/chapter2/animation__how_facilitated_diffusion_works.html

40. Ion Channels

41. Ion channels • Allows ions Ca2+ and Cl- to enter cell • Some are open all the time • Others are gated and will open when • Cell membrane stretches • Electrical signals • Chemical signals

42. Active Transport • REQUIRES ENERGY! • Movement from a LOW concentration to a HIGH concentation!

43. Active Transport • 1. Sodium Potassium Pump • 2. Endocytosis • 3. Exocytosis

44. Active Transport

45. Sodium Potassium Pump • pumps to keep ions in balance • 3 Na+ out for every 2 K+ in • This creates a build up of Na+ outside cell and K+ inside cell forming a net electrical charge across the membrane • Allows for nerve impulses • Contraction of muscles • 1/3 of all energy in animal cells goes to running this pump even as we sleep!

46. Endocytosis

47. Endocytosis • Take in external fluid, macromolecules and other large particles. • Forms “vesicle” some fuse with lysosomes (digestion) others fuse with membrane of other organelles. • 2 Types: a) pinocytosis – cell drinking fluid • b) phagocytosis – cell eats

48. Exocytosisopposite of endocytosis!!