Alanine - The second simplest amino acid, but used the most in proteins.

Arginine - Amino acid often used at the active sites of enzymes. Asparagine - Amide derivative of aspartic acid.

Asparagine - Amide derivative of aspartic acid.

Aspartic Acid - Important intermediate in the citric acid cycle.

Cysteine - Thiol containing amino acid involved in active sites and protein tertiary structure determination.

Glutamic Acid - Negatively charged amino acid found on the surface of proteins.

Glutamine - The only amino acid with the ability to easily cross the barrier between blood and brain tissue.

Glycine - Simplest amino acid that also acts as a neurotransmitter antagonist.

Histidine - Amino acid responsible for histamine biosynthesis.

Isoleucine - Hydrophobic amino acid used almost exclusively in protein and enzyme construction.

Leucine - Another hydrophobic amino acid used almost exclusively in protein and enzyme construction.

Lysine - An essential amino acid with a positive charge on the aliphatic side chain.

Methionine - An essential amino acid that helps initiate protein synthesis.

Phenylalanine - Most common aromatic amino acid found in proteins.

Proline - Cyclic aliphatic amino acid used in the synthesis of collagen.

Serine - Amino acid alcohol found in the active site of serine proteases.

Threonine - Amino acid alcohol involved in porphyrin metabolism.

Tryptophan - Aromatic amino acid used the least frequently in proteins.

Tyrosine - Hydroxyphenyl amino acid that is used to build neurotransmitters and hormones.

Valine - Hydrophobic aliphatic amino acid used to hold proteins together.