Christine - Handout 2 key - TA Christine Yen [email protected]

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TA : Christine Yen Section : Monday 11 AM, HSS 1305 [email protected] OH : Tuesday 12-1 PM, Fireside Lounge BIPN 100: Handout 2 Membrane potentials Why is the resting membrane potential negative? Cells are mainly permeable to K+ due to the presence of K+ leak channels that are always open in their membranes. Since K+ cations are continuously leaving the cell, the inside of the cell is more negative relative to the outside of the outside of the cell. Why is the resting membrane potential of a neuron -70 mV as opposed -90 mV? There are also some Na+ leak channels in the cell membrane so the positive charges being brought into the cell due to the influx of Na+ prevents the cell’s Vm from reaching EK+. However, cell’s permeability K+ is much higher than the cell’s permeability to Na+ so Vm is negative at rest. Nernst Equation Write out the Nernst Equation (for physiological conditions) and describe what it is used for. The Nernst Equation is used to determine the equilibrium potential of any ion. Given the concentrations: [K + ] out =35mM and [K + ] in =3.5μM, find the equilibrium potential of K + . Show your work.
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  • Fall '07
  • French

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