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CELL MEMBRANE

Learn about the cell membrane, its structure, functions, and the movement of substances across it through diffusion, osmosis, and facilitated transport. Discover how water balance is essential for cells in different environments.

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CELL MEMBRANE

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  1. CELL MEMBRANE

  2. Phospholipid CellMembrane • Boundary that separates the living cellfrom it’s non-living surroundings. • Phospholipid bilayer • Amphipathic - having both: hydrophilic heads hydrophobic tails • ~8 nm thick

  3. Transport protein Cell Membrane - cont. • Controls traffic into and out of the cell with phospholipids and transport proteins. • Selectively permeable

  4. Selective Permeability • The property of biological membranes which allows some substances to cross more easily than others.

  5. Fluid Mosaic Model • 1972 - Singer and Nicolson called the membrane a “Fluid Mosaic Model”. • Mosaic: different proteins embedded in the phospholipids. • Fluid: proteins and phospholipids can move freely in the membrane.

  6. Fluid Mosaic Model- cont. • Components of a phospholipid bilayer. 1. phospholipids 2. proteins - enzymes, receptors, transport. 3. glycolipids 4. glycoproteins 5. carbohydrates 6. cholesterol

  7. Animal Cell’s Cell Membrane

  8. What are typical roles of proteins in the cell membrane?

  9. Some Functions of Membrane Proteins

  10. H

  11. What is Diffusion?

  12. Diffusion • The net movement of a substance (molecules) down a concentrationgradientfrom an area of highconcentrationto an area of lowconcentration. • passive transport: NOenergy is expended. • facilitated diffusion: type of passive transport which uses transport proteins.

  13. What is osmosis?

  14. Osmosis • The movement of water across selectively permeable membranes. • The water moves from a high concentrationto low concentration.

  15. Question:What’s in a Solution? Answer: • solute + solventsolution • NaCl + H20saltwater

  16. solution 3% NaCl 5% NaCl 97% H2O 95% H2O Red Blood Cell Hypertonic • A solution with a greater soluteconcentration compared to another solution.

  17. 3% NaCl solution 97% H2O 1% NaCl 99% H2O Red Blood Cell Hypotonic • A solution with a lower solute concentrationcompared to another solution.

  18. The contractile vacuole of Paramecium: an evolutionary adaptation for osmoregulation

  19. Movement of H2O • Water will “ALWAYS”diffuses down a concentration gradient from a HYPOTONICsolution to a HYPERTONICsolution. “ALWAYS REMEMBER” • HYPOTONIC HYPERTONIC • Water flows towards the solutes!!

  20. solution 3%NaCl 97% H2O 3%NaCl 97% H2O Red Blood Cell Isotonic • A solution with an equal solute concentrationcompared to another solution.

  21. Do Water Molecules Stop Moving in Isotonic Conditions? • No. • They continue to diffuse, however there is no net movement! • In general, which way does water move? • From hypotonic to hypertonic!

  22. Elodea in Distilled Water

  23. Elodea in Salt Water

  24. ? ?

  25. Which way will the water move?

  26. WHY?

  27. Water Water plasma membrane Cell Wall Water Plant Cells • When the plasma membrane pulls away from the cell wall(vacuole empty) in a hypertonic environment(loss of water)is called PLASMOLYSIS.

  28. Water Water Central Vacuole Cell Wall Water Plant Cells • Firmness or tension (vacuole full) that is found in plant cells (cell wall) that are in a hypotonic environment is called TURGID. • This process is called TURGOR PRESSURE.

  29. Water Balance in Cells

  30. A watered tomato plant regains its turgor

  31. Red Blood Cells Animal Cells • Animal cells placed into a hypotonic solution will HEMOLYSIS (EXPLODE). • Animal cells placed into a hypertonic solutionwill CRENATE (SHRIVEL). Hemolysis Crenation

  32. Facilitated Diffusion • Diffusion of solutes with the help of transport proteins. (passive transport) • Example: How glucose enters cells • Why do these solutes need a protein to facilitate their diffusion?

  33. That’s right! Because they are too polar or too large to pass through the lipid bilayer

  34. Diffusion and Osmosis Animations http://highered.mheducation.com/sites/9834092339/student_view0/chapter5/how_osmosis_works.html http://highered.mheducation.com/sites/9834092339/student_view0/chapter5/animation_-_osmosis.html http://highered.mheducation.com/sites/9834092339/student_view0/chapter5/how_diffusion_works.html http://highered.mheducation.com/sites/9834092339/student_view0/chapter5/diffusion_through_cell_membranes.html Amoeba Sisters - Cell Membrane https://www.youtube.com/watch?v=L-osEc07vMs&vl=en - Osmosis and Water Potential https://www.youtube.com/watch?v=Ptmlvtei8hw&list=PLM_5CERQ41W9bEVIIUt5n-dnEb9mPGO3W - Cell Transport https://www.youtube.com/watch?v=qBCVVszQQNs&list=PLwL0Myd7Dk1F0iQPGrjehze3eDpco1eVz&index=14 - Inside the Cell  Membrane Facilitated Diffusion Animation http://highered.mheducation.com/sites/9834092339/student_view0/chapter5/how_facilitated_diffusion_works.html

  35. Two Models for Facilitated Diffusion Channel Protein Carrier Protein

  36. Active Transport • The movement of molecules(small or large) across the plasma membrane in which energy (ATP)is required. • Examples: 1. Sodium (Na) - Potassium (K) Pump 2. Exocytosis 3. Endocytosis

  37. Review of Passive and Active Transport:

  38. A transport protein that generates voltage across a membrane is called an electrogenic pump. • One example is the sodium potassium pump

  39. The Sodium-Potassium Pump: a Specific Case of Active Transport

  40. Active Transport Animations: Sodium-Potassium Pump: http://highered.mheducation.com/sites/9834092339/student_view0/chapter5/sodium-potassium_exchange_pump.html http://highered.mheducation.com/sites/0072495855/student_view0/chapter2/animation__how_the_sodium_potassium_pump_works.html Proton Pumps: http://highered.mheducation.com/olc/dl/120068/bio05.swf http://highered.mheducation.com/sites/9834092339/student_view0/chapter5/proton_pump.html Endocytosis and Exocytosis: http://highered.mheducation.com/olc/dl/120068/bio02.swf

  41. Proton pumps are the main electrogenic pumps of bacteria, fungi and plants.

  42. Transport Proteins • Transportsmolecules or ions across biological membranes using active transport. • 3 types of transport proteins: 1. uniport 2. symport 3. antiport

  43. extracellular fluid intracellular fluid Uniport Transport Protein • Carries a single soluteacross the membrane.

  44. extracellular fluid intracellular fluid Symport Transport Protein • Translocates 2 different solutes simultaneously in same direction. • Ex: amino acids that enter the intestine require simultaneous binding of Na and an amino acid to the same transport protein.

  45. extracellular fluid intracellular fluid Antiport Transport Protein • Exchanges 2 solutesby transporting them in opposite directions.

  46. intracellular fluid extracellular fluid K+ K+ Na+ Na+ Sodium-Potassium Pump • This antiport uses energy (active transport) released from splitting ATPto transport Sodium (Na+) out of and Potassium (K+) into cells.

  47. What is cotransport ?

  48. Question: • How are large molecules transported into and out of the plasma membranes?

  49. Answer: • Endocytosis and Exocytosis

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