Proteins are biomolecules composed of alpha- amino acids. An alpha-amino acid has a general formula R-underset(underset(NH_(2))(|))(C)-COOH. The amino acids polymerise and form an amide linkage (peptide linkage) between two monomeric amino acid units. The polymerisation takes place as follows H_(2)N-overset(overset(R_(1))(|))(CH)-underset(underset(O)(||))(C)-OH+H- underset(darr underset((-2H_(2)O))("Polymerisation"))(HN-overset(overset(R_(2))(|))(CH)-underset(underset(O)(||))(C))-OH+H-NH- overset(overset(R_(3))(|))(CH)-underset(underset(O)(||))(C)-OH Two or more similar amino acids can also polymerise, for example a dimer will be like. H_(2)N- overset(overset(R)(||))(CH)-underset(underset(O)(||))(C)-NH-overset(overset(R)(||))(CH)-underset(underset(O)(||))(C)-OH. In the above trimer, if R_(1)=H , R_(2)=CH_(3) & R_(3)=Ph then total number of optically active stereoisomers will be :