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)*log₁₀([ion]_out/[ion]_in), where z is the ion's valence.

This song was originally written for Biology 220 at UW-Seattle, then improved for Biology 351 at UW-Bothell. 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!

• karaoke (by Monty Harper)

• MP3 (by Monty Harper)

• music video

• sheet music (with melody play-back)

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 follow-up activity could be to answer the study questions below. A more extensive interaction with the song might entail (A) learning to sing it, using an audio file and/or sheet music as a guide, and/or (B) illustrating it with pictures, bodily poses, and/or bodily movements. The latter activity could begin with students identifying the most important or most challenging content of the song, and deciding how to illustrate that particular content.

(1) The Nernst equation calculates the equilibrium potential, also known as the Nernst potential. What is that and why is it important in the nervous system?

(2) The song refers to a quotient. What is a quotient?

(3) Does the constant of 58 mV remain the same for all temperatures?

(4) What is ion valence?

(5) What units are carried by the equilibrium potential (E)?

(6) What does the value of E mean?

(7) For many cells, the equilibrium potential of potassium (K⁺) is about -90 mV. For this case, what is the "perfect opposition of the gradients" to which the song refers?

(8) Considering the specific content covered by this song, is there anything important that is missing, unclear, or misleading? If so, what?