Question

Indicate whether the following statements are true or false. If a statement is false, explain why it is false.

A. Van der Waals interactions and hydrophobic interactions are two ways to describe the same type of weak forces that help proteins fold.
B. A large number of noncovalent interactions is required to hold two regions of a polypeptide chain together in a stable conformation.
C. A single polypeptide tends to adopt 3-4 different conformations, which all have equivalent free-energy values (G).

Answer 1

Van der Waals and hydrophobic interactions are not the same; van der Waals are temporary electrostatic attractions, hydrophobic are due to avoidance of water. Noncovalent interactions are necessary to maintain stable protein conformations. A single polypeptide usually adopts a single low-energy conformation for proper function.

Step-by-step explanation:

Statement A is false. Van der Waals interactions and hydrophobic interactions are not the same. While van der Waals interactions occur due to temporary fluctuations in electron density that lead to weak electrostatic attractions between nearby molecules, hydrophobic interactions occur when nonpolar molecules or groups avoid contact with water and aggregate together. These interactions stabilize the protein structure by minimizing the energy cost of exposing nonpolar surfaces to an aqueous environment.

Statement B is true. A large number of noncovalent interactions, including hydrogen bonds, ionic bonds, van der Waals forces, and hydrophobic interactions, work together to maintain the stable conformation of a polypeptide chain in a protein.

Statement C is false. Typically, a single polypeptide does not adopt multiple conformations with equivalent free-energy values. A polypeptide chain will generally fold into a single, most stable three-dimensional structure known as the native conformation, which has the lowest free energy. It is this specific conformation that allows the protein to function properly.