R group.R group determines the unique properties of each amino acid. All amino acids have an amino groups and carboxylic groups, which means that the amino group and carboxylic group do not determine the uniqueness of each amino acid.
A peptide bond is a type of covalent chemical bond linking two amino acids, this is not unique to amino acids. Enzymes are a catalyst that accelerate the chemical reaction. Enzymes are not unique to an amino acids.
1. r group-the r group is what is unique to each amino acid. no two amino acids have identical r groups, although some are very similar (and account for chemical similarities between those amino acids). every amino acid contains one amino group (-nh2) and one carboxylic acid group (-cooh) associated with the central carbon atom of the molecule; so these cannot be the source of any properties unique to each amino acid.
logically, peptide bonds cannot be the correct answer either. the amino acids exhibit characteristic properties as individual molecules. also, the question specifies amino acids and not peptides or proteins.