cell2-membrane_potentials-lectures

# Cell2-membrane_poten - Membrane potentials Membrane potential of cells Every plant and animal cell has a voltage across its plasma membrane called

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1 Membrane potentials Membrane potential of cells Every plant and animal cell has a voltage across its plasma membrane called a membrane potential : ~-70mV (-50 to –100mV) inside . Excitable cells (muscles, neurons) need large changes in their MP in order to function: Non-excitable cells need small changes in their MP in order to function e.g. pancreatic beta-cells, guard cells.

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2 Maintaining membrane potential of Every cell has a voltage across its plasma membrane called a membrane potential: ~-70mV (-50 to –100mV) inside . OUT [K + ] 5 m M [Na + ] 150 m M [Cl ] 120 m M IN [K + ] 140 m M [Na + ] 15 m M [Cl ] 10 m M [A ] 100 m M OUTSIDE CELL Na + K + NaK pump K channel Na channel INSIDE CELL Maintaining membrane potential of The equilibrium potential ( E ion ) is the membrane potential for that particular ion to be at equilibrium. It can be calculated using the Nernst equation: E ion = 60 mV (log[ion] outside /[ion] inside ) –90 mV 140 m M 5 m M KCI KCI K + Cl K channel Membrane selectively permeable to K + Membrane selectively permeable to Na + +62 mV 15 m M NaCI Cl 150 m M NaCI Na + Na channel
3 Maintaining membrane potential of Ions strive to be at equilibrium, but there is more K+ diffusion since there are more K+ leak channels : K + > Cl- > Na + >>Ca2+: K + diffuses out of the cell: membrane potential nears E K+ ; Some Cl- diffuses in, and organic anions trapped inside the cell contribute to the – membrane potential; active transport of K+ restores steady-state levels . • depolarization: more + MP;

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## This note was uploaded on 03/30/2010 for the course BIOLOGY 326 taught by Professor James during the Spring '10 term at York University.

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Cell2-membrane_poten - Membrane potentials Membrane potential of cells Every plant and animal cell has a voltage across its plasma membrane called

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