What does tertiary structure refer to in proteins?

Tertiary structure in proteins refers specifically to the three-dimensional folded structure that arises from the interactions among the various side chains of amino acids in a polypeptide chain. These interactions, which can include hydrogen bonds, ionic bonds, hydrophobic interactions, and van der Waals forces, contribute to the overall shape and functionality of the protein.

Understanding tertiary structure is crucial because it is essential for the protein's function; the specific three-dimensional shape determines how the protein interacts with other molecules. For instance, enzymes' active sites are shaped to fit their substrates precisely, making the conformation that constitutes the tertiary structure vital for biological activity.

In contrast, the arrangement of amino acids relates more to the primary structure, while interactions of multiple protein subunits pertain to quaternary structure. The sequence of nucleotides in a gene is unrelated to protein structure, as it pertains to genetic information rather than the folding and structure of the resulting protein.