A Guide to the Twenty Common Amino Acids

Vocabulary flashcards covering the 20 common amino acids, their side-chain categories, essential status, single and three-letter codes, and special notations.

Amino Acids

Building blocks of proteins in living organisms. There are over $500$ amino acids found in nature, but the human genetic code directly encodes $20$.

Essential Amino Acids

Amino acids that cannot be synthesized in the body and must be obtained from the diet.

Non-Essential Amino Acids

Amino acids that can be synthesized within the body.

Selenocysteine

An amino acid often referred to as the $21\text{st}$ amino acid, which is encoded in a special manner.

asx (B)

The code used when distinguishing between asparagine and aspartic acid is difficult.

glx (Z)

The code used when distinguishing between glutamine and glutamic acid is difficult.

Alanine

An aliphatic, non-essential amino acid with the three-letter code ala and single-letter code A.

Glycine

An aliphatic, non-essential amino acid with the three-letter code gly and single-letter code G.

Isoleucine

An aliphatic, essential amino acid with the three-letter code ile and single-letter code I.

Leucine

An aliphatic, essential amino acid with the three-letter code leu and single-letter code L.

Proline

An aliphatic, non-essential amino acid with the three-letter code pro and single-letter code P.

Valine

An aliphatic, essential amino acid with the three-letter code val and single-letter code V.

Phenylalanine

An aromatic, essential amino acid with the three-letter code phe and single-letter code F.

Tryptophan

An aromatic, essential amino acid with the three-letter code trp and single-letter code W.

Tyrosine

An aromatic, non-essential amino acid with the three-letter code tyr and single-letter code Y.

Aspartic Acid

An acidic, non-essential amino acid with the three-letter code asp and single-letter code D.

Glutamic Acid

An acidic, non-essential amino acid with the three-letter code glu and single-letter code E.

Arginine

A basic, non-essential amino acid with the three-letter code arg and single-letter code R.

Histidine

A basic, essential amino acid with the three-letter code his and single-letter code H.

Lysine

A basic, essential amino acid with the three-letter code lys and single-letter code K.

Serine

A hydroxylic, non-essential amino acid with the three-letter code ser and single-letter code S.

Threonine

A hydroxylic, essential amino acid with the three-letter code thr and single-letter code T.

Cysteine

A sulfur-containing, non-essential amino acid with the three-letter code cys and single-letter code C.

Methionine

A sulfur-containing, essential amino acid with the three-letter code met and single-letter code M.

Asparagine

An amidic, non-essential amino acid with the three-letter code asn and single-letter code N.

Glutamine

An amidic, non-essential amino acid with the three-letter code gln and single-letter code Q.

Guide to the Twenty Common Amino Acids Chart

A reference chart showing chemical structures, single-letter and three-letter codes, side-chain classifications, and essential status for the $20$ common amino acids directly encoded by the human genetic code.