How to memorize the amino acids (+ free Anki deck)

Don’t learn them alphabetically. Learn the codes by their rules: six use their first letter (C, H, I, M, S, V), five took a shared letter because they’re the most common (A, G, L, P, T), and the other nine have reasons you can remember. Then learn the few groups exams love, and drill everything with spaced repetition. The free deck below has all of it.

The codes have rules

The one-letter codes look random until you know how they were chosen. The official IUPAC rules explain all of it:

• First letter, no clash: C cysteine, H histidine, I isoleucine, M methionine, S serine, V valine.
• Shared first letters went to the most common, simplest one: A alanine, G glycine, L leucine, P proline, T threonine.
• Said out loud: F for “Fenylalanine”, R for “aRginine”.
• W for tryptophan, because of its bulky double ring.
• Pairs: D and E for aspartic and glutamic acid, N and Q for asparagine and glutamine.
• K lysine and Y tyrosine: letters close to their initials that were still free.

That’s 20 codes from six rules. Learn the rules once and most codes stop needing memory.

All 20 at a glance

The groups exams ask about

• Negative at body pH: aspartate (D) and glutamate (E).
• Positive at body pH: lysine (K) and arginine (R). Histidine (H) is only partly charged.
• Aromatic: phenylalanine (F), tyrosine (Y) and tryptophan (W).

Textbooks sort the rest (polar or nonpolar) slightly differently, so learn the version your course uses.

My exams asked about all three: the codes, the structures and the groups.

The essential nine

Essential means your body can’t make them, so they have to come from food. MedlinePlus lists nine: histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan and valine. It counts arginine, cysteine, glutamine, tyrosine, glycine, proline and serine as conditionally essential.

The classic mnemonic “PVT TIM HALL” has ten letters because it includes arginine. If your exam says nine, leave the A out.

Free Anki deck

The deck has 70 cards: every amino acid both ways (name to codes, codes to name), essential or not for all 20, and the groups above as cloze cards. We imported it into Anki to check it.

What about the structures?

The deck covers names, codes and groups, not drawings. For structures, draw each one by hand a few times, starting from glycine and adding to the side chain, then make image occlusion cards from your own drawings.

I went straight to Anki cards for mine. If you’re in med school, here’s how I make cards from whole lectures.