Compounds that exhibit this property are said to be chiral. The central carbon atom is said to asymmetric and the two possible forms are said to be stereoisomers or enantiomers Fig. See the following site for more on chiral molecules in nature. The carbon atoms have all been given Greek letter names and any atom attached to on of these core carbon atoms also adopts that name. Other examples of this nomenclature will be presented when studying the individual amino acids.
All amino acids are weak acids with two or more ionizable groups.
Because they are weak acids they serve to buffer the biological fluids. Figure 3 . See the following site for the stereo chemical structures, three letter code and single letter code. These structures do not show the proper ionization states of the amino acids. The next site talks a bit about the properties of the individual amino acids and indicates which ones are essential and those that humans can synthesize.