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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. - PowerPoint PPT Presentation
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Cell Biology 7Cell Biology 7- transport 2- transport 2ndnd
Cell Biology 7Cell Biology 7- transport 2- transport 2ndnd
Sung Youn Lee, PhD. StudentSung Youn Lee, PhD. StudentVeterinary collage, Room 320Veterinary collage, Room 32002 450 3719, 016 293 605902 450 3719, 016 293 6059
leevet@paran.comleevet@paran.com
Cell membrane
Osmosis• Water can freely diffuse across membra
nes in the direction of lower to higher osmolarity.
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
Osmolarity
• Osmolarity=Φic=0.93x2x0.154 =0.286osm/L
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
RBC behave as Almost perfectOsmometer.
Homeostasis• The major osmotic particle in extracellular flui
ds or plasma is Na+ ion.• Na+ is maintained at high concentrations in t
he extracellular fluid by Na/K-ATPase. • If Na/K-ATPase is inhibited by ouabain such t
hat it can no longer pump Na out into the extracelluar fluid, cells swell and then lyse.
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
Donnan effect• After these events, the concentration of protei
n-, 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.
Na+
Na+
Thank you for your attention ~Thank you for your attention ~
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