Apentix/AP Biology/Unit 1: Chemistry of Life/Question
AP Biologymediummcq1 pt

When a water-soluble protein folds, most nonpolar side chains cluster in the core while charged side chains remain on the surface. What drives this sorting?

A.The hydrophobic effect, as burying nonpolar groups frees ordered water molecules and lowers free energy
B.Disulfide bonds that chemically glue every nonpolar side chain to another
C.Peptide bonds that bend toward the center of the folded chain
D.Repulsion between water and the positively charged side chains left outside

Explanation

Core Concept

Nonpolar surfaces exposed to water force nearby molecules into cage-like, low-entropy arrangements. Folding that packs these surfaces together in the interior releases those constrained water molecules into bulk solution, a large entropic payoff that stabilizes the folded state. Charged and polar side chains can afford surface exposure because they form favorable hydrogen bonds and ionic contacts with the solvent. Peptide bonds hold the chain together but do not decide this polar-versus-nonpolar placement.

Correct Answer

AThe hydrophobic effect, as burying nonpolar groups frees ordered water molecules and lowers free energy

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