Ease Into Prep with an MCAT^® Question of the Day

C is the correct answer.

The α-helix is held together primarily by hydrogen bonds between the carboxyl groups and amino groups of amino acids. Disulfide bridges, choice (A), and hydrophobic effects, choice (B), are primarily involved in tertiary structures, not secondary. Even if they were charged, the side chains of amino acids are too far apart to participate in strong interactions in secondary structure.