311DCh36 - Ch. 36 pg. 764-784; Transport in vascular plants...

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Ch. 36 pg. 764-784; Transport in vascular plants Passive transport – diffusion across a membrane; occurs without using metabolic energy Active transport – pumping of solutes across membranes against their electrochemical gradients; cell expends energy in form of ATP Transport proteins – embedded in membrane that solutes use to pass through the membrane; some bind specifically to certain proteins and others provide selective channels Proton pump – active transport protein; uses energy from ATP to pump hydrogen ions out of the cell; results in a proton gradient with higher H+ on outside; pump contributes to membrane potential; inside more negative than outside and membrane potential can be harnessed to perform cellular work; used to move K+ into the cell Cotransport – a transport protein couples the downhill passage of one solute (H+) to the uphill passage of another (NO3-); moves both in together Chemiosmosis – key feature is a transmembrane proton gradient; links energy releasing processes to energy consuming processes in cells Usually run in contrast to ATP synthases, where in this case we use ATP to pump H+ against its gradient Osmosis – the net uptake or loss of water by a cell is controlled; passive transport of water across a membrane Plants have a cell wall that adds physical pressure Water potential – combined effects of solute concentration and physical pressure are incorporated into a measurement called water potential, abbreviated by psi. Potential – waters capacity to perform work when it moves from a region of higher to lower water potential Megapascals – MPa – units of pressure used to measure water potential 1 MPa = 10 atm Solute potential – proportional to the number of dissolved solute molecules; osmotic potential because solutes affect the direction of osmosis; adding solutes lowers the water potential; solute potential is always negative Pressure potential – physical pressure on a solution; can be positive or negative; cell contents press the plasma membrane against the cell wall called turgor pressure Flaccid – regular cell Concentration on outside > inside then water leaves cell by osmosis and cells protoplast will plasmolyze (shrink) Pure water on outside vs. cell – cell will swell (become turgid)
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This note was uploaded on 02/01/2011 for the course BIO 311D taught by Professor Reichler during the Spring '08 term at University of Texas at Austin.

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311DCh36 - Ch. 36 pg. 764-784; Transport in vascular plants...

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