Which of the following describes the overall three-dimensional folding of a polypeptide?

A) Primary structure

B) Secondary structure

C) Quaternary structure

D) Tertiary structure

E) None of the above

Answer: D. Tertiary structure

The tertiary structure of proteins refers to three-dimensional folding of polymer chain. The tertiary structure of a protein indicates the complete three-dimensional arrangement of its polypeptide chain in space. This is usually steadied by outdoor polar hydrophilic hydrogen and ionic bond interactions, and internal hydrophobic interactions flanked by nonpolar amino acid side chains.