Amino Acid Reference Chart

A reference chart for the 20 human amino acids and associated properties. 

Code (1): Refers to each amino acid’s single letter code

Code (3): Refers to each amino acid’s three letter code

pK_a: Refers to the negative logarithm of thedissociation constant for the functional group of the amino acid. Also known asthe pH below which the group is protonated. This can change based on the environment of the amino acid.

pI: Refers to the pH at the amino acid isoelectric point

Property: Often divided into “polar” and “nonpolar” groups; here we provided a more descriptive note on the amino acid functional group chemical and charge properties.

Essential: Refers to whether the amino acid must be obtained from the diet (essential) or can be synthesized in the body (non-essential).