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Membrane Transport&Membrane Potential
Membrane Transport&Membrane Potential
Membrane Transport&Membrane Potential
Membrane Transport&Membrane Potential
Membrane Transport&Membrane Potential
Membrane Transport&Membrane Potential
Membrane Transport&Membrane Potential
Membrane Transport&Membrane Potential
Membrane Transport&Membrane Potential
Membrane Transport&Membrane Potential
Membrane Transport&Membrane Potential
Membrane Transport&Membrane Potential
Membrane Transport&Membrane Potential
Membrane Transport&Membrane Potential
Membrane Transport&Membrane Potential
Membrane Transport&Membrane Potential
Membrane Transport&Membrane Potential
Membrane Transport&Membrane Potential
Membrane Transport&Membrane Potential
Membrane Transport&Membrane Potential
Membrane Transport&Membrane Potential
Membrane Transport&Membrane Potential
Membrane Transport&Membrane Potential
Membrane Transport&Membrane Potential
Membrane Transport&Membrane Potential
Membrane Transport&Membrane Potential
Membrane Transport&Membrane Potential
Membrane Transport&Membrane Potential
Membrane Transport&Membrane Potential
Membrane Transport&Membrane Potential
Membrane Transport&Membrane Potential
Membrane Transport&Membrane Potential
Membrane Transport&Membrane Potential
Membrane Transport&Membrane Potential
Membrane Transport&Membrane Potential
Membrane Transport&Membrane Potential
Membrane Transport&Membrane Potential
Membrane Transport&Membrane Potential
Membrane Transport&Membrane Potential
Membrane Transport&Membrane Potential
Membrane Transport&Membrane Potential
Membrane Transport&Membrane Potential
Membrane Transport&Membrane Potential
Membrane Transport&Membrane Potential
Membrane Transport&Membrane Potential
Membrane Transport&Membrane Potential
Membrane Transport&Membrane Potential
Membrane Transport&Membrane Potential
Membrane Transport&Membrane Potential
Membrane Transport&Membrane Potential
Membrane Transport&Membrane Potential
Membrane Transport&Membrane Potential
Membrane Transport&Membrane Potential
Membrane Transport&Membrane Potential
Membrane Transport&Membrane Potential
Membrane Transport&Membrane Potential
Membrane Transport&Membrane Potential
Membrane Transport&Membrane Potential
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Membrane Transport&Membrane Potential

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  • 1. Membrane Transport and the Membrane Potential www.freelivedoctor.com
  • 2. Extracellular Environment <ul><li>Includes all parts of the body outside of cells </li></ul><ul><ul><li>Cells receive nourishment </li></ul></ul><ul><ul><li>Cells release waste </li></ul></ul><ul><ul><li>Cells interact (through chemical mediators) </li></ul></ul>www.freelivedoctor.com
  • 3. Body Fluids <ul><li>Two compartments </li></ul><ul><ul><li>Intracellular (~67% of body’s H 2 0) </li></ul></ul><ul><ul><li>Extracellular (~33% of body’s H 2 0) </li></ul></ul><ul><ul><ul><li>Blood plasma: about 20% of this </li></ul></ul></ul><ul><ul><ul><li>Tissue fluid (or interstitial fluid) </li></ul></ul></ul><ul><ul><ul><ul><li>Includes extracellular matrix </li></ul></ul></ul></ul><ul><ul><ul><li>Lymph </li></ul></ul></ul>www.freelivedoctor.com
  • 4. Extracellular matrix <ul><li>Connective tissue </li></ul><ul><ul><li>Fibers </li></ul></ul><ul><ul><ul><li>Collegen </li></ul></ul></ul><ul><ul><ul><ul><li>about 15 kinds </li></ul></ul></ul></ul><ul><ul><ul><ul><li>In the basal lamina bind to carbo on plasma membrane </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Then binds to matrix of CT </li></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>Proteoglycans and glycoproteins </li></ul></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>Binds ET to CT </li></ul></ul></ul></ul></ul><ul><ul><ul><li>Elastin </li></ul></ul></ul>www.freelivedoctor.com
  • 5. Extracellular matrix <ul><li>Ground substance </li></ul><ul><ul><ul><li>Interstitial fluid is in the hydrated gel </li></ul></ul></ul><ul><ul><ul><li>Chemically complex </li></ul></ul></ul><ul><ul><ul><ul><li>Molecules linked to the fibers </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Carbohydrates on plasma membrane </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Glycoproteins </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Proteoglycans </li></ul></ul></ul></ul><ul><ul><ul><li>Integrins </li></ul></ul></ul><ul><ul><ul><ul><li>Kind of glycoprotein </li></ul></ul></ul></ul><ul><ul><ul><ul><li>From cytoskeleton to extracellular matrix </li></ul></ul></ul></ul><ul><ul><ul><ul><li>“ glue” cells to matrix </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Relay signals between these compartments </li></ul></ul></ul></ul>www.freelivedoctor.com
  • 6. Transport across cell membrane <ul><li>Plasma (cell) membrane </li></ul><ul><ul><li>Is selectively permeable </li></ul></ul><ul><ul><ul><li>Generally not permeable to </li></ul></ul></ul><ul><ul><ul><ul><li>Proteins </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Nucleic acids </li></ul></ul></ul></ul><ul><ul><ul><li>Selectively permeable to </li></ul></ul></ul><ul><ul><ul><ul><li>Ions </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Nutrients </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Waste </li></ul></ul></ul></ul><ul><ul><li>It is a biological interface between the two compartments </li></ul></ul>www.freelivedoctor.com
  • 7. Transport across cell membrane <ul><li>Plasma (cell) membrane </li></ul><ul><ul><li>Site of chemical reactions </li></ul></ul><ul><ul><ul><li>Enzymes located in it </li></ul></ul></ul><ul><ul><ul><li>Receptors: can bond to molecular signals </li></ul></ul></ul><ul><ul><ul><li>Transporter molecules </li></ul></ul></ul><ul><ul><li>Recognition factors: allow for cellular adhesion </li></ul></ul>www.freelivedoctor.com
  • 8. Transport across cell membrane <ul><li>Transport categories </li></ul><ul><ul><li>Based on structure </li></ul></ul><ul><ul><ul><li>Carrier-mediated </li></ul></ul></ul><ul><ul><ul><ul><li>Facilitated diffusion </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Active transport </li></ul></ul></ul></ul><ul><ul><ul><li>Non-carrier mediated </li></ul></ul></ul><ul><ul><ul><ul><li>Diffusion </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Osmosis </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Bulk flow (pressure gradients) </li></ul></ul></ul></ul><ul><ul><ul><li>Vesicle mediated </li></ul></ul></ul><ul><ul><ul><ul><li>Exocytosis </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Endocytosis </li></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>Pinocytosis </li></ul></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>phagocytosis </li></ul></ul></ul></ul></ul>www.freelivedoctor.com
  • 9. Transport across cell membrane <ul><ul><li>Based on energy requirements </li></ul></ul><ul><ul><ul><li>Passive transport </li></ul></ul></ul><ul><ul><ul><ul><li>Based on concentration gradient </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Does not use metabolic energy </li></ul></ul></ul></ul><ul><ul><ul><li>Active transport </li></ul></ul></ul><ul><ul><ul><ul><li>Against a gragient </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Uses metabolic energy </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Involves specific carriers </li></ul></ul></ul></ul>www.freelivedoctor.com
  • 10. Diffusion and Osmosis <ul><li>Cell membrane separates ICF from ECF. </li></ul><ul><li>Cell membrane is selectively permeable. </li></ul><ul><li>Mechanisms to transport molecules and ions through the cell membrane: </li></ul><ul><ul><li>Carrier mediated transport </li></ul></ul><ul><ul><li>Non-carrier mediated transport </li></ul></ul>www.freelivedoctor.com
  • 11. Diffusion and Osmosis <ul><li>Energy requirements for transport through the cell membrane: </li></ul><ul><ul><li>Passive transport: </li></ul></ul><ul><ul><ul><li>Net movement down a concentration gradient. </li></ul></ul></ul><ul><ul><li>Active transport: </li></ul></ul><ul><ul><ul><li>Net movement against a concentration gradient. </li></ul></ul></ul><ul><ul><ul><li>Requires energy. </li></ul></ul></ul>www.freelivedoctor.com
  • 12. Diffusion <ul><li>Physical process that occurs: </li></ul><ul><ul><li>Concentration difference across the membrane </li></ul></ul><ul><ul><li>Membrane is permeable to the diffusing substance. </li></ul></ul><ul><li>Molecules/ions are in constant state of random motion due to their thermal energy. </li></ul><ul><ul><li>Eliminates a concentration gradient and distributes the molecules uniformly. </li></ul></ul>www.freelivedoctor.com
  • 13. Diffusion Slide number: 1 www.freelivedoctor.com Solute Solvent
  • 14. Diffusion Slide number: 2 www.freelivedoctor.com Solute Solvent
  • 15. Diffusion Slide number: 3 www.freelivedoctor.com
  • 16. Diffusion Slide number: 4 www.freelivedoctor.com
  • 17. Diffusion Through Cell Membrane <ul><li>Cell membrane permeable to: </li></ul><ul><ul><li>Non-polar molecules (0 2 ) </li></ul></ul><ul><ul><li>Lipid soluble molecules (steroids) </li></ul></ul><ul><ul><li>Small polar covalent bonds (C0 2 ) </li></ul></ul><ul><ul><li>H 2 0 (small size, lack charge) </li></ul></ul><ul><li>Cell membrane impermeable to: </li></ul><ul><ul><li>Large polar molecules (glucose) </li></ul></ul><ul><ul><li>Charged inorganic ions (Na + ) </li></ul></ul>www.freelivedoctor.com
  • 18. Rate of Diffusion <ul><li>Dependent upon: </li></ul><ul><ul><li>The magnitude of concentration gradient. </li></ul></ul><ul><ul><ul><li>Driving force of diffusion. </li></ul></ul></ul><ul><ul><li>Permeability of the membrane. </li></ul></ul><ul><ul><ul><li>Neuronal cell membrane 20 x more permeable to K + than Na + . </li></ul></ul></ul><ul><ul><li>Temperature. </li></ul></ul><ul><ul><ul><li>Higher temperature, faster diffusion rate. </li></ul></ul></ul><ul><ul><li>Surface area of the membrane. </li></ul></ul><ul><ul><ul><li>Microvilli increase surface area. </li></ul></ul></ul>www.freelivedoctor.com
  • 19. Osmosis <ul><li>Net diffusion of H 2 0 across a selectively permeable membrane. </li></ul><ul><li>2 requirements for osmosis: </li></ul><ul><ul><li>Must be difference in solute concentration on the 2 sides of the membrane. </li></ul></ul><ul><ul><li>Membrane must be impermeable to the </li></ul></ul><ul><ul><li>solute. </li></ul></ul><ul><ul><li>Osmotically active solutes : solutes that cannot pass freely through the membrane. </li></ul></ul>www.freelivedoctor.com
  • 20. Effects of Osmosis <ul><li>Movement of H 2 0 form high concentration of H 2 0 to lower concentration of H 2 0. </li></ul>www.freelivedoctor.com
  • 21. H 2 0 moves by osmosis into the lower H 2 0 concentration until equilibrium is reached (270 g/l glucose). www.freelivedoctor.com
  • 22. <ul><li>The force that would have to be exerted to prevent osmosis. </li></ul><ul><li>Indicates how strongly the solution “draws” H 2 0 into it by osmosis. </li></ul>www.freelivedoctor.com
  • 23. www.freelivedoctor.com
  • 24. Molality and Osmolality <ul><li>Ratio of solute to H 2 0 critical to osmosis. </li></ul><ul><li>Use molality (1.0 m): </li></ul><ul><ul><li>1 mole of solute is dissolved in 1 kg H 2 0. </li></ul></ul><ul><li>Osmolality (Osm): </li></ul><ul><ul><li>Total molality of a solution. </li></ul></ul><ul><li>Plasma osmolality = 300 mOsm/l. </li></ul>www.freelivedoctor.com
  • 25. <ul><li>NaCl ionized when dissolved in H 2 0 forms 1 mole of Na + and 1 mole of Cl - , thus has a concentration of 2 Osm. </li></ul><ul><li>Glucose when dissolved in H 2 0 forms 1 mole, thus has a concentration of 1 Osm. </li></ul>www.freelivedoctor.com
  • 26. Tonicity <ul><li>The effect of a solution on the osmotic movement of H 2 0. </li></ul><ul><li>Isotonic: </li></ul><ul><ul><li>Equal tension to plasma. </li></ul></ul><ul><ul><li>RBCs will not gain or lose H 2 0. </li></ul></ul>www.freelivedoctor.com
  • 27. Tonicity <ul><li>Hypotonic: </li></ul><ul><ul><li>Osmotically active solutes in a lower osmolality and osmotic pressure than plasma. </li></ul></ul><ul><ul><li>RBC will hemolyse. </li></ul></ul><ul><li>Hypertonic: </li></ul><ul><ul><li>Osmotically active solutes in a higher osmolality and osmotic pressure than plasma. </li></ul></ul><ul><ul><li>RBC will crenate. </li></ul></ul>www.freelivedoctor.com
  • 28. Regulation of Plasma Osmolality <ul><li>Maintained in narrow range. </li></ul><ul><li>Reguatory Mechanisms: </li></ul><ul><li>Osmoreceptors stimulate hypothalamus: </li></ul><ul><ul><li>ADH released. </li></ul></ul><ul><ul><li>Thirst increased. </li></ul></ul>www.freelivedoctor.com
  • 29. Carrier-Mediated Transport <ul><li>Transport across cell membrane by protein carriers. </li></ul><ul><li>Characteristics of protein carriers: </li></ul><ul><ul><li>Specificity: </li></ul></ul><ul><ul><ul><li>Interact with specific molecule only. </li></ul></ul></ul><ul><ul><li>Competition: </li></ul></ul><ul><ul><ul><li>Molecules with similar chemical structures compete for carrier site. </li></ul></ul></ul><ul><ul><li>Saturation: </li></ul></ul><ul><ul><ul><li>Carrier sites filled. </li></ul></ul></ul>www.freelivedoctor.com
  • 30. <ul><li>Transport maximum (Tm): </li></ul><ul><ul><li>Carriers have become saturated. </li></ul></ul><ul><li>Competition: </li></ul><ul><ul><li>Molecules X and Y compete for same carrier. </li></ul></ul>www.freelivedoctor.com
  • 31. Facilitated Diffusion <ul><li>Facilitated diffusion: </li></ul><ul><li>Passive: </li></ul><ul><ul><li>ATP not needed. Powered by thermal energy. </li></ul></ul><ul><ul><li>Involves transport of substance through cell membrane from higher to lower concentration. </li></ul></ul>www.freelivedoctor.com
  • 32. www.freelivedoctor.com
  • 33. Facilitated diffusion Slide number: 1 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Region of lower concentration Region of higher concentration www.freelivedoctor.com Cell membrane Protein carrier molecule Transported substance
  • 34. Facilitated diffusion Slide number: 2 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Region of lower concentration Region of higher concentration www.freelivedoctor.com Cell membrane Protein carrier molecule
  • 35. Facilitated diffusion Slide number: 3 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Region of lower concentration Region of higher concentration www.freelivedoctor.com Protein carrier molecule Transported substance
  • 36. Active Transport <ul><li>Movement of molecules and ions against their concentration gradients. </li></ul><ul><ul><li>From lower to higher concentrations. </li></ul></ul><ul><li>Requires ATP. </li></ul><ul><li>2 Types of Active Transport: </li></ul><ul><ul><li>Primary </li></ul></ul><ul><ul><li>Secondary </li></ul></ul>www.freelivedoctor.com
  • 37. Primary Active Transport <ul><li>ATP directly required for the function of the carriers. </li></ul><ul><li>Molecule or ion binds to carrier site. </li></ul><ul><li>Binding stimulates phosphorylation (breakdown of ATP). </li></ul><ul><li>Conformational change moves molecule to other side of membrane. </li></ul>www.freelivedoctor.com
  • 38. Na + - K + ATP-ase Pump <ul><li>Primary active transport. </li></ul><ul><li>Carrier protein is also an ATP enzyme that converts ATP to ADP and P i . </li></ul>www.freelivedoctor.com
  • 39. P Extracellular fluid 1. Three sodium ions (Na + ) and adenosine triphosphate (ATP) bind to the carrier protein. 2. The ATP breaks down to adenosine diphosphate (ADP) and a phosphate (P) and releases energy. 3 . The carrier protein changes shape, and the Na + are transported across the membrane. 4 . The Na + diffuse away from the carrier protein. 5 . Two potassium ions (K + ) bind to the carrier protein. 6 . The phosphate is released. 7 . The carrier protein changes shape, transporting K + across the membrane, and the K + diffuse away from the carrier protein. The carrier protein can again bind to Na + and ATP. Cytoplasm Na + ATP K + ADP 1 3 Na + Na + K + P K + 4 5 6 7 www.freelivedoctor.com Breakdown of ATP (releases energy) Carrier protein changes shape (requires energy) 2 Carrier protein resumes original shape ATP binding site Carrier protein
  • 40. Extracellular fluid Three sodium ions (Na + ) and adenosine triphosphate (ATP) bind to the carrier protein. Cytoplasm Na + ATP www.freelivedoctor.com ATP binding site Carrier protein
  • 41. P K + ADP Na + The ATP breaks down to adenosine diphosphate (ADP) and a phosphate (P) and releases energy. www.freelivedoctor.com Breakdown of ATP (releases energy)
  • 42. K + Na + The carrier protein changes shape, and the Na + are transported across the membrane. www.freelivedoctor.com Carrier protein changes shape (requires energy)
  • 43. The Na + diffuse away from the carrier protein. Na + www.freelivedoctor.com
  • 44. Two potassium ions (K + ) bind to the carrier protein. K + www.freelivedoctor.com
  • 45. The phosphate is released. P www.freelivedoctor.com
  • 46. The carrier protein changes shape, transporting K + across the membrane, and the K + diffuse away from the carrier protein. The carrier protein can again bind to Na + and ATP. K + www.freelivedoctor.com Carrier protein resumes original shape
  • 47. Secondary Active Transport <ul><li>Coupled transport. </li></ul><ul><li>Energy needed for uphill movement obtained from downhill transport of Na + . </li></ul>www.freelivedoctor.com
  • 48. Secondary Active Transport <ul><li>Cotransport (symport): </li></ul><ul><ul><li>Molecule or ion moving in the same direction. </li></ul></ul><ul><li>Countertransport (antiport): </li></ul><ul><ul><li>Molecule or ion is moved in the opposite direction. </li></ul></ul>www.freelivedoctor.com
  • 49. Membrane Transport of Glucose <ul><li>Glucose transport is an example of: </li></ul><ul><ul><li>Cotransport </li></ul></ul><ul><ul><li>Primary active transport </li></ul></ul><ul><ul><li>Facilitated diffusion </li></ul></ul>www.freelivedoctor.com
  • 50. Bulk Transport <ul><li>Many large molecules are moved at the same time. </li></ul><ul><ul><li>Exocytosis </li></ul></ul><ul><ul><li>Endocytosis </li></ul></ul>www.freelivedoctor.com
  • 51. <ul><li>Proteins and phosphates are negatively charged at normal cellular pH. </li></ul><ul><li>These anions attract positively charged cations that can diffuse through the membrane pores. </li></ul><ul><li>Membrane more permeable to K + than Na + . </li></ul><ul><ul><li>Concentration gradients for Na + and K + . </li></ul></ul><ul><li>Na + / K + ATP pump 3 Na + out for 2 K + in. </li></ul><ul><li>All contribute to unequal charge across the membrane. </li></ul>Membrane Potential www.freelivedoctor.com
  • 52. www.freelivedoctor.com
  • 53. www.freelivedoctor.com
  • 54. <ul><li>Theoretical voltage produced across the membrane if only 1 ion could diffuse through the membrane. </li></ul><ul><li>Potential difference: </li></ul><ul><li>Magnitude of difference in charge on the 2 sides of the membrane. </li></ul>Equilibrium Potentials www.freelivedoctor.com
  • 55. <ul><li>Potential difference of – 90 mV, if K + were the only diffusible ion. </li></ul>www.freelivedoctor.com
  • 56. Nernst Equation <ul><li>Membrane potential that would exactly balance the diffusion gradient and prevent the net movement of a particular ion. </li></ul><ul><li>Equilibrium potential for K + = - 90 mV. </li></ul><ul><li>Equilibrium potential for Na + = + 65 mV. </li></ul>www.freelivedoctor.com
  • 57. Resting Membrane Potential <ul><li>Resting membrane potential is less than E k because some Na + can also enter the cell. </li></ul><ul><li>The slow rate of Na + efflux is accompanied by slow rate of K + influx. </li></ul><ul><li>- 65 mV </li></ul>www.freelivedoctor.com
  • 58. www.freelivedoctor.com

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