3-5 plant transport systems

3-5 plant transport systems - P LANT TRANSPORT SYSTE MS L...

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PLANT TRANSPORT SYSTEMS LIFE 35 35.1.1 Water moves through a membrane by osmosis -The greater the solute concentration of a solution , the more negative its solute potential , and the greater the tendency of water to move into it from another solution of lower solute concentration (and less negative solute potential -As water enters a plant cell due to its negative solute potential , the entry of more water is increasingly resisted by an opposing pressure potential (called turgor pressure in plants ) cell wall prevents lysis water enters plant cells by osmosis until the pressure potential exactly balances the solute potential = turgid (has significant positive pressure potential) -overall tendency of a solution to take up water from pure water, across a membrane = water potential ( ) ψ . The water potential of a solution is simply the sum of its (negative) solute potential ( ψ s ) and its (usually positive) pressure potential ( ψ p ): ψ = ψ s + ψ p -Over longer distances (i.e. xylem vessels and phloem sieve tubes ), the flow of water and dissolved solutes is driven by a gradient of pressure potential , not a gradient of water potential . The movement of a solution due to a difference in pressure potential between two parts of a plant is called bulk flow 35.1.2 Aquaporins facilitate movement of water across membranes - Aquaporins are membrane channel proteins through which water can move without interacting with the hydrophobic environment of the membrane’s phospholipid bilayer (passive) 35.1.3 Uptake of mineral ions requires membrane transport proteins - Mineral ions , which carry electric charges, generally cannot move across a membrane unless they are aided by transport proteins (i.e. ion channels and carrier proteins ). The ions would otherwise be blocked by the hydrophobic
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This note was uploaded on 09/02/2009 for the course BIO 315H taught by Professor Payne during the Spring '08 term at University of Texas at Austin.

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3-5 plant transport systems - P LANT TRANSPORT SYSTE MS L...

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