What defines the tertiary structure of a protein?

The tertiary structure of a protein is defined by its final three-dimensional shape. This structure results from the complex folding of a single polypeptide chain, influenced by various interactions among its side chains, including hydrogen bonds, ionic bonds, hydrophobic interactions, and disulfide bridges. The unique three-dimensional configuration is critical because it determines the protein's functionality, including how it interacts with other molecules. Proteins must fold correctly to perform their specific biological activities, and this precise folding into tertiary structure is essential for their roles in cellular processes.

Other options describe different aspects of protein structure; for instance, the chain of amino acids refers to the primary structure, the arrangement of multiple polypeptide chains pertains to quaternary structure, and the bonding between amino acids relates to the interactions that stabilize the primary structure. Each of these components plays its role in protein formation, but it is the tertiary structure that defines the overall shape crucial for function.