The amino acids are small molecules, monomers of peptides and proteins. They are crystalline, almost all sweet and present isomerism, since they have an asymmetric carbon linked to four different radicals (except in the case of glycine or glycine). These radicals are:
- A carboxyl group (-COOH), acidic.
- An amino group (-NH2), basic.
- A hydrogen.
- A radical, characteristic of each amino acid, and which gives it its own characteristics. They serve as criteria for the classification of amino acids.
The carboxyl group is always at one end, but the amino group can occupy different positions. Thus, α, β, γ,… amino acids are distinguished, depending on the position of the amino group with respect to the carbon of the carboxyl group. In nature, both the amino and the carboxyl groups are attached to the same carbon , so they are amino acids of type α or α-amino acids.