Final answer:
The initial regular folding of a polypeptide represents its secondary structure, predominantly the alpha-helix and beta-pleated sheet, stabilized by hydrogen bonds.
Step-by-step explanation:
The initial folding of a polypeptide into a regular repeating shape represents its secondary structure. This structure forms from hydrogen bonding of the peptide backbone, which causes the amino acids to fold into patterns such as the α-helix and β-pleated sheet. These hydrogen bonds typically form between the oxygen atom in the carbonyl group of one amino acid and another amino acid that is four residues away. The stability and pattern of these structures are critical for the protein's overall function and shape.