\[E=\frac{RT}{zF}\ln\left(\frac{C_o}{C_i}\right)\]
Variables
ENernst potential (V)
Runiversal gas constant (J/mol·K)
Tabsolute temperature (K)
zionic charge number
FFaraday constant (C/mol)
Coextracellular ion concentration
Ciintracellular ion concentration
Description
What is this formula?
The Nernst equation calculates the equilibrium electrical potential generated by the concentration gradient of a specific ion across a membrane.
When to use it
Use this formula in biophysics, physiology, neuroscience, or electrochemistry when analyzing ion transport and membrane potentials.
Example
Calculate the potassium equilibrium potential at:
T=310 K
z=1
Co=5 mmol/L
Ci=140 mmol/L
Constants:
R=8.314 J/mol·K
F=96485 C/mol
Formula:
E=((R*T)/(z*F))*ln(Co/Ci)
Substitution:
E=((8.314*310)/(1*96485))*ln(5/140)
Result:
E≈-0.089 V
The equilibrium potential is approximately -89 mV.
Applications
- Neuron membrane analysis
- Cardiac electrophysiology
- Ion channel studies
- Cellular biophysics
- Electrochemical systems