Amino acids

Click a residue for its structure and pKa ladder.

Nonpolar / hydrophobic · 7

Greasy side chains that cluster in the protein core.

GAVLIMP, or, with the aromatics folded in, "Grandma Always Visits London In May For Winston's Party." London is nowhere near the poles.

Aromatic · 3

Ring side chains. All three absorb ultraviolet light; Trp and Tyr dominate at 280 nm, Trp most strongly.

W F Y. Say it fast: "wifey." You put a ring on it.

Polar, uncharged · 5

Neutral at pH 7 but hydrogen-bonding, so usually on the solvent-facing surface.

Santa's Team Crafts New Quilts: Ser, Thr, Cys, Asn, Gln. Add "Yearly" if you file tyrosine here instead of with the aromatics.

Negatively charged (acidic) · 2

Carboxylate side chains, deprotonated and −1 at pH 7.

Both end in "-ate": aspartATE, glutamATE. And the -ate is the ionized acid.

Positively charged (basic) · 3

Basic side chains. Lys and Arg are positive at pH 7; histidine mostly is not.

Basic HAL: His, Arg, Lys. The knights riding horses, positively noble.

Groupings

Set	Members	Note
Essential PVT TIM HaLL	Phe · Val · Thr · Trp · Ile · Met · His · Arg · Leu · Lys	Nine are strictly essential in adults. The lowercase "a" is the tell: Arginine is only conditionally essential, needed during growth, pregnancy and illness, but the urea cycle makes enough otherwise. In one-letter codes the strict nine spell "WTF HaVe MILK."
Purely ketogenic onLy Lysine and Leucine are pureLy ketogenic	Leu · Lys	Leucine and lysine become acetyl-CoA or acetoacetate. Because pyruvate dehydrogenase is irreversible, acetyl-CoA can never become glucose, the same reason fatty acids cannot.
Glucogenic and ketogenic PITTT	Phe · Ile · Thr · Trp · Tyr	Everything not listed here or above is purely glucogenic. Default to glucogenic and memorize only the exceptions. PITTT spells names (P = Phe, as in PVT TIM HALL); in one-letter codes the set is F I T W Y.
Aromatic W F Y. Say it fast: "wifey." You put a ring on it.	Trp · Phe · Tyr	Tryptophan and tyrosine absorb at 280 nm, which is how protein concentration gets measured.
Sulfur-containing Cys and Met carry the Sulfur, but only Cys's free -SH can cross-link	Cys · Met	Cysteine forms disulfide bonds; methionine's sulfur is locked in a thioether. Methionine is the start codon.
Hydroxyl-containing S-T-Y: Ser, Thr, Tyr, where kinases park their phosphates	Ser · Thr · Tyr	The three residues that get phosphorylated. For the two plain alcohols: "alcohol is a SERious THReat."
Polar, uncharged STaCk QuiN: Ser, Thr, Cys, Gln, Asn	Ser · Thr · Cys · Gln · Asn	Polar side chains that carry no charge at physiological pH, so they hydrogen-bond freely. Ser and Thr take phosphates; Cys forms disulfide bonds; Asn and Gln are the amides of Asp and Glu.
Polar, charged DEHKR, said "decker": D and E acidic, H K R basic	Asp · Glu · His · Lys · Arg	D and E are acidic (negative); H, K and R are basic (positive by class). Also remembered as "Dragons Eat Knights Riding Horses." Histidine is grouped here by chemistry, but is mostly uncharged at physiological pH.
Branched-chain "I Love Vermont" maple syrup: Ile, Leu, Val	Ile · Leu · Val	All three essential, all branched at the side chain. Their shared breakdown enzyme fails in maple syrup urine disease, which makes the urine smell sweet. For the MCAT, know which three are branched.
Quirkily coded QWKYNERD, the "quirky nerd" eight whose one-letter code is not their initial	Gln · Trp · Lys · Tyr · Asn · Glu · Arg · Asp	The other twelve simply use their first letter. Q-tamine, double-ring W, K next to L, tYrosine, asparagiNe, glutEmate, aRginine, asparDic.