If compartment A represents the inside of a cell and compartment B the extracellular fluid, then with [K]i = 100 mM and [K]o = 10 mM as in the example above calculate the equilibrium potential for potassium.
If compartment A represents the inside of a cell and compartment B the extracellular fluid, then with [K]i = 100 mM and [K]o = 10 mM as in the example above calculate the equilibrium potential for potassium.
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To calculate the equilibrium potential for potassium (K⁺), you can use the Nernst equation, which is given by:
[ E_{K} = frac{RT}{zF} ln left( frac{[K]_{o}}{[K]_{i}} right) ]
Where:
– ( E_{K} ) is the equilibrium potential for potassium.
– ( R ) is the universal gas constant (8.314 J/(mol·K)).
– ( T ) is the temperature in Kelvin (usually 310 K for physiological conditions).
– ( z ) is the charge of the ion (+1 for K⁺).
– ( F ) is Faraday’s constant (96485 C/mol).
For simplicity, at physiological temperature (37°C or 310 K), you can also use the simplified version of the Nernst equation:
[
E_{K} approx 61.5 , text{mV} cdot log left( frac{[K]_{o}}{[K]_{i}} right)
]
Plugging in the values:
– ([K]_{o} = 10 , text{mM})
– ([K]_{i} = 100 , text{mM})
We get:
[
E_{K} approx 61.5 , text{m