Which of the following amino acids has a positively charged guanidinium group?
Arginine is the accurate classification or categorization for the organism, molecule, or concept described in this question. In Amino_Acids_Structure, proper classification is based on shared characteristics including morphological, biochemical, genetic, and evolutionary criteria. Arginine meets the specific diagnostic features and defining criteria that distinguish it from related groups. The other options (Lysine, Histidine, and Glutamate) belong to different taxonomic groups, represent different classification levels, or possess distinct characteristics that exclude them from this category.
Ref: Campbell Biology, Urry et al., 12th Ed.