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Cell Biology 7 - transport 2 nd

Cell Biology 7 - transport 2 nd. Sung Youn Lee, PhD. Student Veterinary collage, Room 320 02 450 3719, 016 293 6059 leevet@paran.com. Cell membrane. Osmosis. Water can freely diffuse across membranes in the direction of lower to higher osmolarity. Osmotic pressure Van ’ t Hoff ’ s law.

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Cell Biology 7 - transport 2 nd

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  1. Cell Biology 7- transport 2nd Sung Youn Lee, PhD. Student Veterinary collage, Room 320 02 450 3719, 016 293 6059 leevet@paran.com

  2. Cell membrane

  3. Osmosis • Water can freely diffuse across membranes in the direction of lower to higher osmolarity.

  4. Osmotic pressureVan’t Hoff’s law • Osmotic pressure (∏) = iRTc • i=number of ions (glucose 1, NaCl 2, MgCl2 3) • R=ideal gas constant (8.3145 J/mol K ) • T=absolute temperature (K=C+273.16 ) • C=molar concentration

  5. Osmolarity • Osmolarity=Φic=0.93x2x0.154 =0.286osm/L

  6. Tonicity • Isotonic fluid = 0.3osm/L • NaCl ; 0.15mole/L=(23+35.5)x0.15 =58.5x0.15=8.8g/L ≒ 0.9% NaCl • Glucose(C6H12O6)=(12x6+1x12+16x6)x0.3 =(72+12+96)=180x0.3=54g/L ≒ 0.5% dextrose

  7. RBC behave as Almost perfect Osmometer.

  8. Homeostasis • The major osmotic particle in extracellular fluids or plasma is Na+ ion. • Na+ is maintained at high concentrations in the extracellular fluid by Na/K-ATPase. • If Na/K-ATPase is inhibited by ouabain such that it can no longer pump Na out into the extracelluar fluid, cells swell and then lyse.

  9. Donnan effect and its relation to water flow • These impermeable anion (protein & RNA) cause a redistribution of permeable anions in a manner predicted by Donnan and Gibbs. • To maintain electroneutrality

  10. Donnan effect • After these events, the concentration of protein-, Cl-, and K+ will be higher in compartment A, therefore, water will flow toward compartment A. • For this same reason, the Donnan effect tends to cause water to flow into cells but is balanced by active outward pumping of ions by Na/K-ATPase.

  11. Na+ Na+

  12. Thank you for your attention ~

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