Based on Donnan equilibrium, what is the contribution to the resting membrane potential of the concentration imbalance of Potassium ions?[the typical internal Potassium concentration is about 150 mM, the external one about 5 mM; the prefactor for monovalent ions is about 61.5 mV]
Question
Based on Donnan equilibrium, what is the contribution to the resting membrane potential of the concentration imbalance of Potassium ions?[the typical internal Potassium concentration is about 150 mM, the external one about 5 mM; the prefactor for monovalent ions is about 61.5 mV]
Solution
The resting membrane potential contribution of the concentration imbalance of Potassium ions can be calculated using the Nernst equation.
The Nernst equation is: E = RT/zF * ln([ion]out/[ion]in)
Where:
- E is the equilibrium potential
- R is the universal gas constant (8.314 J/(mol*K))
- T is the temperature in Kelvin (assume 298K for room temperature)
- z is the valence of the ion (for Potassium, z=1)
- F is Faraday's constant (96485 C/mol)
- [ion]out and [ion]in are the external and internal concentrations of the ion
Given that the typical internal Potassium concentration is about 150 mM and the external one about 5 mM, and the prefactor for monovalent ions is about 61.5 mV, we can substitute these values into the Nernst equation.
However, since we are dealing with room temperature and monovalent ions, we can simplify the Nernst equation to: E = 61.5 mV * log([ion]out/[ion]in)
Substituting the given values, we get: E = 61.5 mV * log(5 mM / 150 mM)
Solving this equation will give us the contribution to the resting membrane potential of the concentration imbalance of Potassium ions.
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