Amino Acids Tests

QUALITATIVE ANALYSIS OF AMINO ACIDS AND PROTEINS

Amino acids are molecules containing an amine group, a carboxylic acid group and a side chain that
varies between different amino acids. Amino acids of the general formula RCH(NH2)COOH are
amphoteric, behaving as amines in some reactions and as carboxylic acids in others. At a certain pH
known as the isoelectric point an amino acid has no overall charge, since the number of protonated
ammonium groups (positive charges) and deprotonated carboxylate groups (negative charges) are
equal. Since the amino acids at their isoelectric points have both negative and positive charges, they
are known as zwitterions.
Amino acids are critical to life. They have particularly important functions like being the building
blocks of proteins and being the intermediates in metabolism.
Amino acids are generally classified by the properties of their side chain into four groups. The side
chain can make an amino acid a weak acid or a weak base, and a hydrophile if the side chain is polar
or a hydrophobe if it is nonpolar.