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22 Cards in this Set
- Front
- Back
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Why are proteins necessary to increase permeability?
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Ion and other transporters regulate molecule concentrations on each side.
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Membrane potential (Vm - voltage of membrane) dependent on what?
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K+ permeability
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What is resting potential?
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-70 mV
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What are the four factors contributing to the resting membrane potential?
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1. [cations] + [anions] = 0 for both inside and outside cell.
2. Selective permeability due to presence of ion channels. 3. Osmotic neutrality where [solutes]in = [solutes]out 4. Active transport of Na+ and K+ |
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When is Gibbs-Donnan equilibrium achieved?
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[solutes] inside = [solutes] outside
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Describe the diffusion rate of ion channels and why?
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FAST b/c molecules don't bind to anything.
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What type of transport channels are always open.
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Passive ion channels
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Equation for Nernst Eq.
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Resting potential on ion
= (RT/zF) ln ([solutes]outside / [solutes]inside) |
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Equation for membrane resting potential for ions specific in mammal at 37 C.
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z 61.5 mV log ([ion]outside/[ion]inside)
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Active transport of Na+ and K+ contributes how many mV to the resting membrane potential?
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Approx. 3mV
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Increasing potassium potential outside the cell will lead to what in Vm? why? What happens to these cells?
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Depolarization
b/c Vm seeks more positive Ek Cells get hyperexcitability |
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Low potassium concentration outside leads to what? and what physical manifestation?
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Hyperpolarization and paralysis
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What is the Goldman-Hodgkins-Katz eq.
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NOTE Permeability variables and lack of z
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Equilibrium potential for sodium
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-60 mV
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Equilibrium potential for potassium
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+90 mV
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Equilibrium potential for calcium
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+120 mV
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Equilibrium potential for chloride
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-75 mV
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What is the reversal potential?
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E(ion)
Max potential due to diffusion of single ionic species |
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Ratio of K+ inside over outside
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40
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Ratio of Na+ outside over inside
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10
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Ratio of Cl- outside over inside
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10
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Why is the typical resting membrane potential (Vm) a steady state potential and not an equilibrium potential?
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Because energy is required to maintain it.
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