Practice Questions

Protein function depends on proper folding into the native three-dimensional structure.

The heme prosthetic group contains Fe²⁺, which reversibly binds oxygen.

β-sheets are classified according to the orientation of adjacent strands.

Histidine's pKa is close to physiological pH, making it ideal for acid-base catalysis.

Chaperones bind exposed hydrophobic regions of unfolded proteins, preventing aggregation and promoting correct folding.

Heat disrupts weak interactions but usually leaves the covalent peptide backbone intact.

Collagen contains the repeating sequence Gly-X-Y. Glycine occurs every third residue, allowing tight packing of the triple helix.

Quaternary structure exists only in proteins composed of more than one polypeptide chain, such as hemoglobin.

The hydrophobic effect causes non-polar side chains to cluster in the interior, minimizing contact with water and stabilizing the folded structure.

In an α-helix, the carbonyl oxygen of residue i hydrogen bonds with the amide hydrogen of residue i+4, producing the stable helical conformation.