Semi-Permeable Membrane

This parody (written by Greg Crowther) is sung to the tune of "Semi-Charmed Life" (written by Stephan Jenkins and performed by Third Eye Blind).

A fundamental concept of cell biology is that of semi-permeable membranes, which let some substances through while preventing others from passing. The semi-permeable nature of cell membranes allows cells to exchange nutrients and wastes with the blood while otherwise maintaining control over their own contents.

Whether a given molecule can get through a cell membrane depends on such factors as the size and polarity of the molecule. In general, relatively small, nonpolar molecules can diffuse directly through the membrane, while other substances must use a channel or transporter for facilitated diffusion or active transport.

The lyrics below are for a highly condensed version of the original song that includes a verse ("Well, it's about time..."), the second pre-chorus ("How do I get through..."), a chorus ("I want something else..."), a short rap bridge ("It's not just a mood..."), and a whole lot of doo-doo-dooting.

Doo-doo-doot, doo-doo-doot-doo,
Doo-doo-doot, doo-doo-doot-doo,
Doo-doo-doot, doo-doo-doot-doo,
Doo-doo-doot!

Well, it's about time to take this script and flip it.
I'm here at the cell membrane full of lipid.
Can't lick it; I wanna skip it.
It repels me, and I'm livid!

You see, the N's and O's I wear
Don't share fair
When it comes to electron pairs.
Look there!
They're hogging electron pairs like an ogre;
The bonds are polar -- game over!

How do I get through
This lipid wall to the cytosol?
How do I get through?
Transporters, give me a call!

I want something else
To get me through this
Semi-permeable membrane, baby, baby!
I want something else;
These lipids need a kiss
Goodbye!

Doo-doo-doot, doo-doo-doot-doo,
Doo-doo-doot, doo-doo-doot-doo,
Doo-doo-doot, doo-doo-doot-doo,
Doo-doo-doot!

I've been labeled
And misconstrued,
But I'm in a polar mood,
With a lipophobic attitude!
It's not rude --
It's biochemistry, dude!

Doo-doo-doot, doo-doo-doot-doo,
Doo-doo-doot, doo-doo-doot-doo,
Doo-doo-doot, doo-doo-doot-doo,
Doo-doo-doot!

• MP3

• music video

• sheet music

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) What is a semi-permeable membrane, in general? Give a non-biological example of a semi-permeable membrane.

(2) The narrator says that lipid "repels me." Assuming that the narrator is a molecule, what can we infer about its chemical structure? What other details of the song support this idea?

(3) The lyrics include the line, "The N's and O's I wear don't fair share when it comes to electron pairs." What are N's and O's in this context? What does the narrator's statement mean scientifically?

(4) The narrator refers to the cell membrane as a "lipid wall." This isn't a bad two-word description; in what sense is this misleading?

(5) The narrator refers to its own chemical structure as "lipophobic." Provide 1-2 synonyms for this word.

(6) Could the narrator be a protein? Why or why not? Cite evidence from the song.

(Answers may be found on the answers page.)