Potassium Reversal Potential Lab Report

This experiment was performed in order to test if Potassium reversal potential is a good predictor of membrane potential. We predicted that even though there are many ions in and around a cell, reversal potassium of Potassium will give a good estimate of the membrane potential. In order to test our hypothesis, we measured the membrane potential across crayfish muscle fibers that were submerged in different saline solutions containing varied potassium concentrations. We also calculated the reversal potential of Potassium for those concentrations using Nernst equation. After running a t-test between the recorded membrane potential and calculated Nernst values, we found out that they were significantly different. For lower potassium concentrations, membrane potential was better predicted by Sodium reversal potential, and for higher Potassium concentration, Chloride reversal potential was a better predictor of the membrane potential. Rather than calculating different reversal potentials for

The reversal potential for an ion calculated using Nernst equation predicts the membrane potential if the membrane was completely permeable to that ion and not at all to others. So, in our experiment, if the difference in potentials recorded and potentials calculated from Nernst equation is not significant, we can conclude that K+ ions are primary predictors of the membrane potential. If the difference is significant, we can conclude that other ions are also involved in determining the membrane potential of a cell, and that Nernst equation might not be the best in predicting the membrane potentials. A better equation that takes into consideration the contributions of other ions as well, such as the Goldman equation, should be used while predicting membrane