This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Physiology
Equilibrium potential for an ion is calculated using: 
Select and explain. 
A. Gibbs-Donnan equation, B. Nerst equation, C. Goldman equation, D. None
B: Nerst equation
Answer: B: Nerst equation 
Explanation: B i.e. Nernst equation Equilibrium potential (i.e., membrane potential at which equilibrium b/w concentration & electrical gradient exist) for any (one) univalent ion is calculated by Nernst equationQ and for several different ions by Goldmann- Hodgkin-katz equation.