Chemistry - Biomolecules Question with Solution | TestHub

The primary structure of a protein refers to the linear sequence of amino acids.

The secondary structure refers to the local folded structures that form within a polypeptide due to interactions between atoms of the backbone. The most common types of secondary structures are the $\alpha$-helix and the $\beta$-pleated sheet.

The tertiary structure is the overall three-dimensional structure of a polypeptide.

The quaternary structure is the arrangement of multiple folded protein or coiling protein molecules in a multi-subunit complex.

Therefore, the $\alpha$-helix is found in the secondary structure of proteins.

Answer: Secondary structure