Question

1. Using the Nernst equation, calculate the equilibrium potential for Ca21 and for Cl2 from the following sets of data: a. Given [Ca21]o 5 1 mM, [Ca21]i 5 100 nM, find ECa21 b. Given [Cl2]o 5 110 mM, [Cl2]i 5 10 mM, find ECl2

Answer 1

Answer : The value of $E_{Ca^{2+}}=-61mV$ and $E_{Cl^{-1}}=-31.8mV$

Explanation :

To calculate the equilibrium potential we are using Nernst equation:

$E_{ion}=\frac{61}{z}\times \log (\frac{C_o}{C_i})$

where,

$E_{ion}$  = equilibrium potential

z = valency of ion

$C_o$ = concentration of the ion outside the cell

$C_i$ = concentration of the ion inside the cell

Part a :

Given:

z = valency of ion $Ca^{2+}$ = 2

$C_o$ = concentration of the ion outside the cell = 1 mM

$C_i$ = concentration of the ion inside the cell = 100 mM

$E_{Ca^{2+}}=\frac{61}{2}\times \log (\frac{1mM}{100mM})$

$E_{Ca^{2+}}=-61mV$

Part b :

Given:

z = valency of ion $Cl^{-1}$ = 1

$C_o$ = concentration of the ion outside the cell = 110 mM

$C_i$ = concentration of the ion inside the cell = 10 mM

$E_{Cl^{-1}}=\frac{61}{2}\times \log (\frac{110mM}{10mM})$

$E_{Cl^{-1}}=-31.8mV$