A Level Biology Practice Exam 2025 – 400 Free Practice Questions to Pass the Exam

The correct choice highlights the characteristic features of secondary structure in proteins, which refers specifically to the localized folding and coiling patterns within the polypeptide chain. These structures are primarily stabilized by hydrogen bonds that occur between the backbone of the amino acids. Common types of secondary structures include alpha-helices and beta-pleated sheets.

In contrast, the sequence of amino acids in the chain describes the primary structure, while the overall three-dimensional shape pertains to the tertiary structure of the protein. The interactions between multiple polypeptide chains are indicative of quaternary structure. Understanding these distinctions is crucial for grasping how proteins achieve their functional forms.