Alpha helices and beta sheets are associated with which protein structural level?

Alpha helices and beta sheets are critical features of the secondary structure of proteins. Secondary structure refers to local folding patterns that occur due to hydrogen bonding between the backbone atoms in the polypeptide chain. In an alpha helix, the structure coils in a right-handed spiral, stabilized by hydrogen bonds between every fourth amino acid. Meanwhile, beta sheets consist of strands of amino acids lying adjacent to each other, forming a sheet-like arrangement stabilized by hydrogen bonds between the backbone of different strands.

These structures are distinct from the primary structure, which is simply the linear sequence of amino acids in a polypeptide chain. The tertiary structure refers to the overall three-dimensional shape of a single polypeptide chain that arises from interactions among various side chains, and quaternary structure pertains to the assembly of multiple polypeptide chains into a functional protein complex. Thus, alpha helices and beta sheets are hallmark features specifically associated with the secondary level of protein structure.