5. The table below shows the intracellular and extracellular concentrations of s

Question

5. The table below shows the intracellular and extracellular concentrations of several ions in a cell at rest, along with the relative membrane permeability of the cell to the ions Intracellular Extracellular Membrane Concentration Concentration Permeability (mM) 140 15 4 0.0001 (mM) 4 145 110 5 ion At rest Na+ Cl- Ca++ 0.05 0.1 0 a. What is the equilibrium potential of calcium, in mV? b. What is the resting membrane potential of the cell, in mV? c. Suppose that the cell contains ligand gated calcium channels. When calcium binds

Explanation / Answer

1. +134 mV

2. -70 mV

3. calcium will move out from the cell because of active transport.This will occur to maintain the steep calcium electrochemical gradient across the cell membrane.

4. The calcium channel will remain closed at resting membrane potential. But when it opens the membrane gets depolarized. The GHK equation states the ionic flux across the membrane as a function of transmembrane potential and the concentration of the ion inside and outside of the cell.If the outside concentration is more the ions will move out through a channel as the membrane permeability for calcium is zero.That is justified with GHK equation statement.

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