Questions: The alpha helix and beta pleated sheet are examples of protein A primary structure. (B) quaternary structure. (C) tertiary structure. (D) gamma structure. (E) secondary structure.

The answer is (E): secondary structure.

Explanation for each option:

A. Primary structure: This refers to the linear sequence of amino acids in a protein chain. It does not describe the folding or spatial arrangement of the protein.

B. Quaternary structure: This refers to the arrangement and interaction of multiple protein subunits in a multi-subunit complex. It is a higher level of organization than secondary structure.

C. Tertiary structure: This refers to the overall three-dimensional shape of a single protein molecule, including how its secondary structures (alpha helices and beta sheets) fold and interact with each other.

D. Gamma structure: This is not a recognized term in the context of protein structure.

E. Secondary structure: This refers to the local folding patterns within a protein, such as alpha helices and beta pleated sheets, which are stabilized by hydrogen bonds.

Summary: The alpha helix and beta pleated sheet are examples of secondary structure in proteins.