A muscle cell has an intracellular of 14 mM and an extracellular of 140 mM. Assuming that 2.3 /F = 60 mV, what would the membrane potential be if the muscle cell membrane were permeable only to Na+?
Nernst equation Used to calculate the equilibrium potential for a single ion. In applying the Nernst equation, we assume that the membrane is freely permeable to that ion alone. ENa+ = 2.3 /zF log Ce/Ci ENa+ = 60 mV log 140/14 = 60 mV log 10 ENa+= 60 mV. Notice that the signs were ignored and that the higher concentration was simply placed in the numerator to simplify the log calculation. To determine whether ENa+ is +60 mV or -60 mV,- Use the intuitive approach= Na+ will diffuse from extracellular to intracellular fluid down its concentration gradient, making the cell interior positive.
+80 mV
-60 mV
-80 mV
+60 mV
Cell Membrane and transpo protiens