Question

which of the following levels of protein structure involves more than one polypeptide chain?
primary
quaternary
secondary
tertiary

Explanation:

Protein structure has four levels. Primary is the linear sequence of amino - acids. Secondary involves local folding like alpha - helices and beta - sheets. Tertiary is the 3 - D structure of a single polypeptide chain. Quaternary structure is formed by the association of multiple polypeptide chains.

Answer:

B. quaternary