Answer:
The folding of polypeptide begin during translation of the polypeptide chain. Amino acids interact with each other to form three dimensional tertiary structure and secondary structure elements formed spontaneously as an intermediate before the formation of tertiary structure.
There are two common secondary structure elements formed that are alpha helices(α helix) and beta pleated sheets ( β pleated sheet). Both the structures are attcahed by a hydrogen bond which is present between amino hydrogen and carboxyl oxygen atoms in the peptide backbone.
Hence, the two common elements of secondary structure are alpha helices and beta sheets.