Which sentence best explains how the R group (side chain) determines an amino acid's unique chemical behavior?

The R group differs among amino acids and confers properties such as size, charge, polarity, and ability to form special bonds, thereby influencing local interactions and overall protein structure.

The R group always donates a proton, making all amino acids acidic and indistinguishable in terms of folding tendencies and interactions.

The R group contains the peptide bond that links adjacent amino acids and therefore determines whether amino acids can be incorporated into proteins.

The R group is identical for all amino acids except glycine, so primary sequence is the only determinant of tertiary structure.