The  secondary structure of a protein is generated by hydrogen bonds between atoms of the polypeptide backbone.
A hydrogen bond is an intramolecular attraction between a hydrogen atom in one molecule and an electronegative atom (e.g., oxygen) of another molecule.The most common types of secondary structures in proteins are alpha helices and beta sheets.In alpha helices, the carbonyl group of one amino acid is bonded to the amino group of another amino acid spaced four residues apart in the polypeptide chain.In beta-sheets, different regions of the polypeptide line up next to each other, thereby these protein regions interact by hydrogen bonds.
In conclusion, the secondary structure of a protein is generated by hydrogen bonds between atoms of the polypeptide backbone.
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