The Nernst Equation
by Greg Crowther
Find the concentrations of ions out and in;
Figure out the quotient, and take the log (base 10).
Multiply by a constant like 58 mV;
Divide by ion valence to find potential E.
At the voltage you have found (says Walther Nernst),
There's no flux in or out (says Walther Nernst)!
This song reminds students of the Nernst equation for calculating an ion's equilibrium potential. In its simplest form, the Nernst equation says that, at 20 degrees Celsius (293 Kelvin), for a given ion, E_{ion} = (58 mV/z)*log_{10}([ion]_{out}/[ion]_{in}), where z is the ion's valence (electric charge). Note that the "constant" of 58 millivolts is only constant for a temperature of 20 degrees C; you can use a value of 61 mV for a temperature of 37 degrees C.
This song was written for BIOL 220 at the University of Washington. The melody is loosely based on "I Want You Back" as recorded by the Jackson 5. (The words "says Walther Nernst" correspond to the words "I want you back" in the original.)
• MP3 (demo)
• score (with melody playback)
• video
