Cl equil-v:
Only chloride may cross a membrane separating two compartments.
At a temperature of 26∘C, the concentrations of chloride ions are:
intracellular: 70
extracellular: 485
What is the equilibrium potential?
Give a numeric answer within 1%, in mV.
To calculate the equilibrium potential (Eᵢ), we can use the Nernst equation:
Eᵢ = (RT/zF) * ln([Cᵢ]/[Cₒ])
Where:
- Eᵢ is the equilibrium potential
- R is the ideal gas constant (8.314 J/(mol·K))
- T is the temperature in Kelvin
- z is the valence of the ion (charge)
- F is the Faraday constant (96500 C/mol)
- [Cᵢ] is the intracellular concentration of the ion
- [Cₒ] is the extracellular concentration of the ion
First, let's convert the temperature from Celsius to Kelvin:
T = 26°C + 273.15 = 299.15 K
The valence (z) of chloride ion (Cl⁻) is -1.
Now, we can plug the values into the equation:
Eᵢ = (8.314 J/(mol·K) * 299.15 K / (-1 * 96500 C/mol)) * ln(70/485)
Calculating this equation, we get:
Eᵢ ≈ -65.81 mV
Therefore, the equilibrium potential for chloride ions, assuming no other ions are present and Cl⁻ is the only ion able to cross the membrane, is approximately -65.81 mV.
Please note that the Nernst equation assumes ideal conditions and may not fully capture the complexities of biological systems.