This is a nutrition through the life cycle 6th edition pdf article. Follow the link for more information. This article is about the class of chemicals.
Many important proteinogenic and non-proteinogenic amino acids have biological functions. The first few amino acids were discovered in the early 19th century. The unity of the chemical category was recognized by Wurtz in 1865, but he gave no particular name to it. 20 common amino acids is about 2. 20 common α-amino acids is about 9.
But at pH between 2. Amino acids exist as zwitterions also in the solid phase, and crystallize with salt-like properties unlike typical organic acids or amines. The variation in titration curves when the amino acids can be grouped by category. With the exception of tyrosine, using titration to distinguish among hydrophobic amino acids is problematic.