. For a typical cell that is 100 equation to determine the potential change that

Question

. For a typical cell that is 100 equation to determine the potential change that would be produced by a doubling of the extracellular K+ concentratio times more permeable to K* than to any other ion, use the Goldman n. (Use appropriate concentrations from the previous question). HINTS: Use 58 in the Goldman equation for results in mV or 0.058 for results in V. Because this problem is about change (one value relative to another), you do not need to know the permeabilities of individual ions; you only need to know that PK is 100 times higher than PNa and PCI Be careful how to handle [Ct] because of its negative charge.

Explanation / Answer

Goldman Equation = k*log ( ions outside the membrane/ ions inside the membrane)

Vm = RT/F log {pK (K+)o + pNa (Na+)o +pCl (Cl-)i / pK (K+)i + pNa (Na+)i +pCl (Cl-)o}

Here,
Vm is membrane potential
R is the universal gas constant (8.314 J/K/mol)
T is temperature in Kelvin
F is Faradays constant (96485 C/mol)
px is permeability for the specific ions
(K+) is the ion concentration for Potassium.

The position of Chlorine in and Chlorin out is inverted because it is a negative ion and it reverses the effect on the voltage potential.

Since we are only talking about the movement of only one elemental ions, i.e. Potassium; we do not have to enter the values for Sodium and Chlorine as their permeability would be 0

Let permeability of Na+ and Cl- be 1 each.
Now permeability of K+ will be 100
It is also given that the extracellular concentration of K+ is double the intracellular concentration
The concentrations of Chloride and Sodium ions is also usually higher in the extracellular region compared to the intracellular region at resting potential.

So, putting the values in at Room temperature, assuming the values for Cl and Na with consistent ratios

Vm = 8.314*293/ 96485 log { 100*2 + 1*1.5 + 1*1 / 100*1 + 1*1 + 1*1.6 }

= 0.025 log {1.97}

= 0.00736V

The above potential change is based on assumed values based on the nature of concentration gradients found in a normal cell, as exact values were not given.

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