**3.7. Qualitative screening of proteins and amino acids**

Proteins are involved in all physiological processes that take place in all living cells. Proteins are colloidal, do not diffuse through the plasma membrane, are irreversible coagulated upon heating and are insoluble in neutral salts [30].

Amino acids are amphoteric phytocompounds, highly reactive, with an amino and carboxylic acid moiety, therefore, being mostly water soluble.
