The Nernst Equation
by Greg Crowther
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.
This song was originally written for Biology 220 at the University of Washington. The melody is based on "I Want You Back" as recorded by the Jackson 5.
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, z, to find potential E.
No net flow goes in or out (forces are balanced)
For whichever individual ion we're talking about.
Two driving forces cancel out (cancel out, baby)!
Perfect opposition of the gradients closes the spout.
This is what we've learnst,
All thanks to Walther Nernst!
• MP3 (by Monty Harper)
• sheet music (with melody playback)
• video
• video for karaoke
Songs like this one can be used during class meetings and/or in homework assignments. Either way, the song will be most impactful if students DO something with it, as opposed to just listening.
An initial, simple followup activity could be to answer the study questions below. A more extensive interaction with the song might entail (A) learning to sing it, using the audio file and/or sheet music as a guide, or (B) designing kinesthetic movements ("dance moves") to embody it. The latter activity should begin with students identifying the most important or most challenging content of the song, and deciding how to illustrate that particular content.
(1) Does the constant of 58 mV remain the same for all temperatures?
(2) What is ion valence?
(3) What units are carried by the equilibrium potential (E)?
(4) What does the value of E mean?
(Answers may be found on the answers page.)
