2. Regents Biology Human Physiology: Unit-1 Source: Collected from various sources on the internet and modified by Dr Boominathan Ph.D. BY DR BOOMINATHAN Ph.D. M.Sc.,(Med. Bio, JIPMER), M.Sc.,(FGSWI, Israel), Ph.D (NUS, SINGAPORE), PDF (USA) PONDICHERRY UNIVERSITY IV Lecture 9/August/2012 Cell Membranes transport across cell and membrane

3. Regents Biology 2006-2007 Cell Membranes & Movement Across Them

4. Regents Biology Cell (plasma) membrane  Cells need an inside & an outside…  separate cell from its environment  cell membrane is the boundary IN food - sugars - proteins - Lipids -salts -O 2 -H 2 O OUT waste - ammonia - salts - CO 2 - H 2 O products - proteins cell needs materials in & products or waste out

5. Regents Biology Building a membrane  How do you build a barrier that keeps the watery contents of the cell separate from the watery environment? What substance do you know that doesn’t mix with water?  LIPIDS  Remember: oil & water don’t mix!!

6. Regents Biology Lipids of cell membrane  Membrane is made of special kind of lipid  phospholipids  Membrane is a double layer  phospholipid bilayer inside cell outside cell lipid “repelled by water” “attracted to water” phosphate

7. Regents Biology Semi-permeable membrane  Cell membrane controls what gets in or out  Need to allow some materials — but not all — to pass through the membrane  semi-permeable  only some material can get in or out aa H2OH2O sugar lipidssalt waste So what needs to get across the membrane? O2O2

8. Regents Biology Crossing the cell membrane  What molecules can get through the cell membrane directly?  fats and oils can pass directly through inside cell outside cell lipid salt aa H2OH2O sugar waste but… what about other stuff?

9. Regents Biology Cell membrane channels  Need to make “doors” through membrane  protein channels allow substances in & out  specific channels allow specific material in & out  H 2 O channel, salt channel, sugar channel, etc. inside cell outside cell sugaraa H2OH2O salt waste

10. Regents Biology How do you build a semi-permeable cell membrane?  Channels are made of proteins  proteins both “like” water & “like” lipids bi-lipid membrane protein channels in bi-lipid membrane

11. Regents Biology Protein channels  Proteins act as doors in the membrane  channels to move specific molecules through cell membrane HIGH LOW

12. Regents Biology Movement through the channel  Why do molecules move through membrane if you give them a channel? ? ? HIGH LOW

13. Regents Biology Molecules move from high to low  Diffusion  move from HIGH to LOW concentration

14. Regents Biology Diffusion  Move from HIGH to LOW concentration  passive transport  no energy needed diffusionosmosis diffusion of water

15. Regents Biology Diffusion (without energy-simple)  Move from HIGH to LOW inside cell outside cell Which way will Lipid substances move? LOW HIGH Lipid

16. Regents Biology Facilitated Diffusion  Move from HIGH to LOW through a channel inside cell outside cell sugar Which way will sugar move? sugar LOW HIGH

17. Regents Biology Diffusion  Move from HIGH to LOW concentration  directly through membrane  simple diffusion  no energy needed  help through a protein channel  facilitated diffusion (with help)  no energy needed HIGH LOW

18. Regents Biology Simple vs. facilitated diffusion inside cell outside cell lipid inside cell outside cell H2OH2O simple diffusionfacilitated diffusion H2OH2O protein channel

19. Regents Biology Active transport  Cells may need molecules to move against concentration “hill”  need to pump “uphill”  from LOW to HIGH using energy  protein pump  requires energy  ATP ATP

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21. Transport summary simple diffusion facilitated diffusion active transport ATP

22. Regents Biology 2006-2007 Osmosis Movement of Water Across Cell Membrane

23. Regents Biology Osmosis  Water is very important, so we talk about water separately  Osmosis  diffusion of water from HIGH concentration of water to LOW concentration of water  across a semi-permeable membrane

24. Regents Biology Keeping water balance  Cell survival depends on balancing water uptake & water loss freshwaterbalancedsaltwater

25. Regents Biology Keeping right amount of water in cell  Freshwater  a cell in fresh water  high concentration of water around cell  cell gains water  example: Paramecium  problem: cells gain water, swell & can burst  water continually enters Paramecium cell  solution: contractile vacuole  transports water out of cell freshwater No problem, here Burst 1

26. Regents Biology Keeping right amount of water in cell  Saltwater  a cell in salt water  low concentration of water around cell  cell loses water  example: shellfish  problem: cell loses water  in plants: plasmolysis  in animals: shrinking cell  solution: take up water saltwater I will survive! I’m shrinking, I’m shrinking! 2

27. Regents Biology Keeping right amount of water in cell  Balanced conditions  no difference in concentration of water between cell & environment  cell in equilibrium  example: blood  problem: none  water flows across membrane equally, in both directions  volume of cell doesn’t change balanced I could be better… That’s better! 3

28. Regents Biology CELLS

29. Regents Biology Downloaded from: StudentConsult (on 15 August 2012 04:30 AM) Chemical compositions of extracellular and intracellular fluids

30. Regents Biology Na-K Channel: How it Works A type of active transport. 3 sodium ions move out of cell 2 potassium ions move into cell. ATP is needed as each of these ions are moving against their conc. gradient. Mostly used in cardiac muscle and nervous tissue. Maintains Na+K gradient concentration. Huge amount of ATP goes into this NaK channel.

31. Regents Biology Sodium –Potassium Channel Figure 3.11

32. Regents Biology Sodium-Potassium Channel A molecule of ATP is used with each “swap of Na/K ions

33. Regents Biology Endocytosis (phagocytosis-Cell Eating)  This is Vessicle transport during which the entire plasma membrane folds inward allowing large particles into the cell.  Ex; the cell is ingesting microbes, perhaps?

34. Regents Biology AS Biology, Cell membranes and Transport 33 Cell Membrane - Function - Endocytosis The cell membrane can also engulf structures that are much too large to fit through the pores in the membrane proteins this process is known as endocytosis. In this process the membrane itself wraps around the particle and pinches off a vesicle inside the cell. In this animation an ameba engulfs a food particle.

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36. Exocytosis  The opposite of ENDOcytosis. Large particles are leaving the cell. (digested microbes for example).

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38. Receptor- Mediated Endocytosis  Viruses are species – specific, and receptor specific,  transmitted via receptor-mediated endocytosis.

39. Regents Biology AS Biology, Cell membranes and Transport 38 Vesicle-mediated transport Vesicles and vacuoles that fuse with the cell membrane may be utilized to release or transport chemicals out of the cell or to allow them to enter a cell. Exocytosis is the term applied when transport is out of the cell. VesiclesvacuolesExocytosis

40. Regents Biology Cell Membrane (Transport) Notes Cell Membrane and Cell Wall: ALL cells have a cell membrane made of proteins and lipids Cell Membrane lipid bilayer protein channel protein pump Layer 1 Layer 2 SOME cells have cell membranes and cell walls – ex: plants, fungi and bacteria Cell Membrane Cell Wall

41. Regents Biology Plant cells have a cell wall made of cellulose – that cellulose is fiber in our diet Bacteria and fungi also have cell walls, but they do not contain cellulose Cell membranes and cell walls are porous allowing water, carbon dioxide, oxygen and nutrients to pass through easily

42. Regents Biology Function of the Cell Membrane: Cell membrane separates the components of a cell from its environment—surrounds the cell “Gatekeeper” of the cell—regulates the flow of materials into and out of cell—selectively permeable Cell membrane helps cells maintain homeostasis— stable internal balance

43. Regents Biology Passive Transport A process that does not require energy to move molecules from a HIGH to LOW concentration DDiffusion FFacilitated Diffusion OOsmosis

44. Diffusion is the movement of small particles across a selectively permeable membrane like the cell membrane until equilibrium is reached. These particles move from an area of high concentration to an area of low concentration. outside of cell inside of cell

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46. Osmosis is the diffusion of water through a selectively permeable membrane like the cell membrane Water diffuses across a membrane from an area of high concentration to an area of low concentration. Semi-permeable membrane is permeable to water, but not to sugar

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49. Facilitated Diffusion is the movement of larger molecules like glucose through the cell membrane – larger molecules must be “helped” Proteins in the cell membrane form channels for large molecules to pass through Proteins that form channels (pores) are called protein channels outside of cell inside of cell Glucose molecules

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51. Hypertonic Solutions: contain a high concentration of solute relative to another solution (e.g. the cell's cytoplasm). When a cell is placed in a hypertonic solution, the water diffuses out of the cell, causing the cell to shrivel. Hypotonic Solutions: contain a low concentration of solute relative to another solution (e.g. the cell's cytoplasm). When a cell is placed in a hypotonic solution, the water diffuses into the cell, causing the cell to swell and possibly explode. Isotonic Solutions: contain the same concentration of solute as another solution (e.g. the cell's cytoplasm). When a cell is placed in an isotonic solution, the water diffuses into and out of the cell at the same rate. The fluid that surrounds the body cells is isotonic.

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54. Active Transport Active transport is the movement of molecules from LOW to HIGH concentration. Energy is required as molecules must be pumped against the concentration gradient. Proteins that work as pumps are called protein pumps. Ex: Body cells must pump carbon dioxide out into the surrounding blood vessels to be carried to the lungs for exhale. Blood vessels are high in carbon dioxide compared to the cells, so energy is required to move the carbon dioxide across the cell membrane from LOW to HIGH concentration. outside of cell inside of cell Carbon Dioxide molecules

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56. NO ENERGY NEEDED: Diffusion Osmosis Facilitated Diffusion ENERGY NEEDED: Active Transport ANALOGY:

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58. Food is moved into the cell by Endocytosis Wastes are moved out of the cell by Exocytosis Endocytosis and Exocytosis is the mechanism by which very large molecules (such as food and wastes) get into and out of the cell

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60. Ex: White Blood Cells, which are part of the immune system, surround and engulf bacteria by endocytosis.