Question

The three-dimensional shape of a protein is determined by the primary, secondary, tertiary, and in many cases, the quaternary structure of the protein. The following sentence is taken from scientific articles on protein structure. Choose the level of protein structure that applies best to the sentence.

Hydrogen bonds between peptide 'backbone' amino groups and carboxyl groups of one polypeptide and the R-groups of another polypeptide, contribute to the overall function of the protein.

Answer 1

The sentence describes the quaternary structure of proteins, which involves interactions, such as hydrogen bonds, between multiple polypeptide chains that affect the protein's overall function.

Step-by-step explanation:

The level of protein structure described in the sentence is the quaternary structure. It refers to the interactions and bonding, such as hydrogen bonds, between different polypeptide chains, contributing to the protein's function. Quaternary structure involves the assembly of multiple polypeptide subunits, which are often tertiary structures, into a larger complex.

The hydrogen bonds that stabilize the quaternary structure may involve backbone amino groups and carboxyl groups, as well as interactions involving the R-groups (side chains) of the amino acids. This level of structure is critical because it dictates how protein subunits come together and function as a whole, like in the case of hemoglobin, which has two alpha and two beta chains that form its quaternary structure. Hemoglobin's ability to transport oxygen is directly related to the way these subunits interact and stabilize each other through bonds.