Final answer:
Secondary structures in proteins, such as the α-helix and β-pleated sheet, are stabilized by hydrogen bonds within the polypeptide backbone and are pivotal for protein function but do not include side chain interactions.
Step-by-step explanation:
The secondary structures of a polypeptide chain refer to the local, regular structures stabilized by hydrogen bonds between atoms in the peptide backbone, primarily involving the carbonyl and amino groups. The most common types of secondary structures are the α-helix and the β-pleated sheet. In an α-helix, hydrogen bonds form between the oxygen of a carbonyl group and the hydrogen of an amino group four residues down the chain, creating a right-handed spiral. In contrast, β-pleated sheets are formed when the polypeptide chain folds back on itself, or between adjacent chains, with hydrogen bonds stabilizing the sheet structure. These secondary structures are crucial for the protein's functionality but do not include the side-chain interactions which contribute to the tertiary structure of the protein.