(by Eric Vesper, taken from a girl on the track team's im profile)
The simplest of acids has got to be Glycine
And if it's a long one, it's probably Lysine
Alanine's simple, its has just one methyl
Valine is bigger; it's one methylethyl
And Aspartic Acid has one CH2 there
But if it's Glutamic, why then there are two there
Tryptophan, Tyrosine both have their rings
And, too, Phenylalanine, one of those things
If you like hydroxyls then Serine's your chain
And, if that one's taken, Threonine remains
Arginine has an abundance of N's
Just like Asparagine (Glutamine's friend)
Cysteine has sulfur, pK eight-point-three
Methionine's sulfur binds with CH3
Histidine flip-flops when mildly acid
Leucine is bulky and also quite placid
Then there's Isoleusine, which branches quite early
And finally Proline, whose structure's quite squirrelly.
So if it's an acid whose name is one we know
Chances are good the acid's amino