zoo_523_probset2-08

zoo_523_probset2-08 - Zoo 523 Problem set 2 d ue 2008 Sept...

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Zoo 523 Problem set 2 2008 due Wednesday Sept 17th 1. An artificial membrane has a resistance of 5 X 10 4 ohms. If a current of 0.01 milliamps flows across the membrane, what is the voltage across the membrane? IxR=V (0.01x10 -3 amps) x (5x10 4 ohms) = 0.5 volts=500 mV 2. During a nerve signal, the voltage across the membrane changes by 95 mV. What is the change in charge across the membrane? Q=CV C m =1(μF/cm 2 ) Q=1x10 -6 (F/cm 2 )x0.095V= 9.5x10 -8 Coulombs per cm 2 of membrane 3. A cell membrane permeable only to potassium ions has an internal K ion concentration of 300mM and an external K ion concentration of 20 mM. What is the potential across the membrane? E k = (RT/F) ln([K o ]/[K i ]) At 20 º C, E k =58 x log([K2] / [K1]) E k =58xlog(20/300) E k = approx. -68.21 mV 4. What experiments would you do to show that the lipids in the internal leaflet and the external leaflet of a cell membrane are chemically different?
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First, a cellular membrane must be obtained. This can be done by preparing empty red
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zoo_523_probset2-08 - Zoo 523 Problem set 2 d ue 2008 Sept...

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