Final answer:
The initial folding of a polypeptide chain into a regular repeating shape is known as its secondary structure, driven by hydrogen bonding in the peptide backbone forming structures like the α-helix and β-pleated sheet.
Step-by-step explanation:
The initial folding of a polypeptide into a regular repeating shape represents its secondary structure. This folding is primarily the result of hydrogen bonding between elements of the peptide backbone. These hydrogen bonds cause the amino acids to fold into repeating patterns such as the α-helix and β-pleated sheet structures. The secondary structure is a crucial organizational level following the primary structure, which is the linear sequence of amino acids. Subsequent folding into the tertiary structure involves interactions between the amino acid side chains further leading to the protein's three-dimensional shape, which is essential for its function.