P. The molecule consists of two polypeptide chains joined and folded around one another.

Q. The sequence and number of amino acids in each polypeptide chain.

R. The amino acids in each chain are coiled into αhelix and stabilized by hydrogen bonds. Which order is described by each statement?

• (A) P - Quaternary, Q - Secondary, R - Tertiary.
• (B) P - Primary, Q - Tertiary, R - Secondary.
• (C) P - Secondary, Q - Tertiary, R - Primary.
• (D) P - Quaternary, Q - Primary, R - Secondary.

Solution

P. "The molecule consists of two polypeptide chains joined and folded around one another."

This statement describes the quaternary structure of the protein, which is the arrangement of multiple polypeptide chains (subunits) in the overall protein structure. The quaternary structure is the highest level of protein structure.

Q. "The sequence and number of amino acids in each polypeptide chain."

This statement describes the primary structure of the protein, which is the linear sequence of amino acids in the polypeptide chain. The primary structure is the lowest level of protein structure.

R. "The amino acids in each chain are coiled into αhelix and stabilized by hydrogen bonds."

This statement describes the secondary structure of the protein, which is the local, regular folding of the polypeptide chain into structures like α-helices and βsheets, stabilized by hydrogen bonds. The secondary structure is the second level of protein structure