Hemoglobin is largely α-helical; which statement about α-helix stabilization is most accurate for this protein?
- Hydrogen bonds form between backbone C=O and N–H groups along the helix (correct answer)
- Hydrogen bonds form primarily between charged side chains across the helix core
- Covalent bonds between adjacent residues lock the helix into place
- Ionic bonds between N-terminus groups create the helical twist
Explanation: This question tests the understanding of secondary protein structures, specifically stabilization in α-helical proteins like hemoglobin. Secondary structures are stabilized by hydrogen bonds: α-helices form between the backbone amide hydrogen and carbonyl oxygen four residues apart, while β-sheets involve hydrogen bonds between strands. Here, the emphasis is on how hydrogen bonds maintain the α-helix in hemoglobin. The correct answer notes that hydrogen bonds form between backbone C=O and N–H groups along the helix, crucial for structural integrity. A common distractor might emphasize side-chain or covalent bonds, which are not primary for secondary structure. Teaching strategies include comparing hemoglobin's subunits to show conserved helical motifs. Encouraging analysis of mutations affecting helices deepens understanding of stability and disease implications.