Final answer:
Adjacent polypeptides interact through H-bonding in the secondary structure, forming either an alpha-helix or a beta-pleated sheet which are critical for protein function.
Step-by-step explanation:
Structures are formed where adjacent polypeptides interact through H-bonding between the peptide bonds of the secondary structure. This can take the form of an alpha-helix or a beta-pleated sheet, and is maintained by hydrogen bonds between amino acids in different regions of the original polypeptide strand. The secondary structure is crucial in the overall folding and function of a protein molecule.The answer to this question is b) Secondary structure. Secondary structure refers to the local folding patterns within a polypeptide chain, such as alpha-helices and beta-pleated sheets. These secondary structures are held together by hydrogen bonds between the peptide bonds of adjacent amino acids.
This is different from the primary structure (a), which is the sequence of amino acids in the polypeptide chain, and the tertiary structure (c), which is the overall 3D shape of a protein molecule.
Quaternary structure (d) refers to the interactions between multiple polypeptide chains to form a functional protein complex.