A different amino acid sequence leads to which change in protein structure?

• A. The same tertiary structure
• B. Different tertiary structure
• C. Different primary structure
• D. No change

Answer: (B)

Amino acid sequence determines how a polypeptide folds into a three‑dimensional shape. The specific side chains set up which interactions can form—hydrophobic packing, hydrogen bonds, ionic interactions, and disulfide bridges. If you change residues, you alter these interactions, which can rearrange the folding pattern and stabilize a different three‑dimensional arrangement. So the result is a different tertiary structure. While changing the sequence is itself a change in the primary structure, the question asks about the resulting structural level, which is the tertiary structure.