Identifying Protein Amino Acid Interactions

Steps:

• Pair X features polar side chains (e.g., serine-oxygen or nitrogen), enabling hydrogen bonding via shared electrons.
• Pair Y shows nonpolar side chains (e.g., leucine or valine), leading to hydrophobic interactions to minimize water contact.
• Pair Z displays oppositely charged side chains (e.g., aspartate-lysine), forming an ionic bond through electrostatic attraction.
• Match these to option B: hydrogen bond for X, hydrophobic for Y, ionic for Z.

Why B is correct:

• Aligns with amino acid properties: polar groups H-bond, nonpolar aggregate hydrophobically, charged pairs attract ionically per Coulomb's law.

Why the others are wrong:

• A: Misassigns X as hydrophobic; polar chains form H-bonds, not avoid water.
• C: Swaps X and Y; X is polar (H-bond), Y nonpolar (hydrophobic).
• D: Identical to C, so same mismatch on X and Y assignments.

Final answer: B