(A )The alpha helix is a right-handed coiled structure formed by hydrogen bonds between the amino and carboxyl groups of the peptide bond.

(B) The alpha helix is stabilized by the optimal geometry of the hydrogen bonds, which maximizes the number of stabilizing interactions.

(C) The alpha helix is characterized by a specific amino acid sequence that includes high proportions of alanine, leucine, glutamic acid, and lysine.

(D) The alpha helix is one of the most common secondary structures found in proteins, contributing to their overall stability and function.

Solution

Option C is incorrect.

While it is true that the alpha helix is characterized by a specific amino acid sequence, it is not accurate to state that it includes high proportions of alanine, leucine, glutamic acid, and lysine. Instead, amino acids with small, nonpolar side chains such as alanine, leucine, and valine are more likely to form alpha helices. Amino acids like proline and glycine are less likely to form alpha helices due to their structural properties.