Which of the following is an example of secondary structure in proteins?

The identification of α-helices and β-sheets as an example of secondary structure in proteins is accurate because these structures represent specific arrangements of amino acids in a polypeptide chain that contribute to the overall stability of the protein. Secondary structures are characterized by regular patterns of hydrogen bonding that occur between the backbone atoms in the polypeptide chain.

In α-helices, the carbonyl oxygen of one amino acid forms hydrogen bonds with the amide hydrogen of an amino acid four residues earlier in the sequence, leading to a coiled structure. In contrast, β-sheets consist of strands of amino acids aligned side by side, stabilized by hydrogen bonds between the backbone carbonyl and amide groups of adjacent strands.

These secondary structural elements are crucial for the protein's overall shape and function, serving as foundational building blocks for the more complex tertiary and quaternary structures that arise from interactions among multiple polypeptides or with other molecules.