Each amino acid has a different what that contributes to its properties?

• A. Backbone
• B. R group
• C. Peptide bond
• D. Nucleic acid

Answer: (B)

The side chain (the R group) of an amino acid is what gives each one its distinct properties. This variation in size, polarity, and charge among the side chains determines how an amino acid behaves in water, how it interacts with other residues, and how it influences protein folding and function. The backbone part of every amino acid and the peptide bonds that join them are the same across all amino acids, so they don’t account for the differences in properties. Nucleic acid is not part of amino acid structure. For example, some side chains are nonpolar and hydrophobic, others are polar, and some carry a charge at physiological pH, which all drives the diverse chemistry of proteins.