ContractileVacuole

ContractileVacuole - 9/22/10 Contrac0le vacuole • ...

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Unformatted text preview: 9/22/10 Contrac0le vacuole •  Osmo0c component πcytoplasm >πout Notes on contrac0le vacuole Contrac0le vacuole •  Osmo0c component –  Small vesicles near plasma membrane πcytoplasm = πvesicle Plasma membrane Water enters cell by osmosis across semipermeable plasma membrane Plasma membrane cytoplasm vesicles Contrac0le vacuole •  Osmo0c component cytoplasm –  Small vesicles near plasma membrane –  Load vesicles with salt transport salt vesicles 1 9/22/10 Contrac0le vacuole Contrac0le vacuole •  Osmo0c component •  Transi0on –  Small vesicles near plasma membrane –  Load vesicles with salt –  Water follows salt, vesicle swells –  Water dilutes out salt, so that πvesicle πcytoplasm H2O –  Decrease Pw of vesicle membrane Contrac0le vacuole Contrac0le vacuole •  Transi0on •  Transi0on –  Decrease Pw of vesicle membrane –  Transport salt out salt transport –  Decrease Pw of vesicle membrane –  Transport salt out –  Cvesicle decreases πcytoplasm > πvesicle –  Water cannot follow quickly 2 9/22/10 Contrac0le vacuole •  Mechanical pump –  Vesicle associates with ac0n microfibrils at plasma membrane Contrac0le vacuole •  Mechanical pump –  Vesicle fuses to plasma membrane –  Ac0n contracts –  Forces water out by bulk flow Contrac0le vacuole •  Mechanical pump –  Vesicle migrates to plasma membrane –  Associates with ac0n microfibrils –  Vesicle fuses to plasma membrane Contrac0le vacuole •  Mechanical pump –  Water leaves by bulk flow –  Carries solutes with it –  Decreases volume of cell 3 9/22/10 Contrac0le vacuole •  Mechanical pump –  Decreases volume of cell –  Because πvesicle < πcytoplasm, raises πinside. Steps of process •  Isosmo0c water movement –  Salt transport alters π –  Water follows rapidly because Pw is high. •  Decrease in Pw •  Bulk flow Steps of process •  Isosmo0c water movement •  Decrease in Pw –  Vesicle contents can now alter π –  Can be maintained out of equilibrium for a 0me •  Bulk flow Steps of process •  Isosmo0c water movement •  Decrease in Pw –  Vesicle out of equilibrium •  Bulk flow –  Non ­osmo0c movement=>not driven by Δπ –  Moves vesicle contents quickly past cytoplasm so they don’t have 0me to come to equilibrium. 4 ...
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This note was uploaded on 09/16/2011 for the course BIO 203 taught by Professor Loretz during the Fall '09 term at SUNY Buffalo.

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