Where do hydrogen bonds form in a protein's secondary structure?

In a protein's secondary structure, hydrogen bonds are crucial for stabilizing specific shapes like alpha helices and beta sheets. These bonds form specifically between the hydrogen atom of the amine group (NH) of one amino acid and the oxygen atom of the carbonyl group (C=O) of another. This interaction occurs within the backbone of the protein, rather than involving the side chains or the primary sequence of amino acids directly.

The formation of these hydrogen bonds is what enables the protein to fold into its secondary structure, providing it with necessary stability and facilitating functional conformations. The other choices refer to configurations that do not directly contribute to the hydrogen bonding patterns that characterize secondary structure. Non-polar side chains, for example, do not engage in hydrogen bonding as they lack the polar functional groups needed for such interactions.