Final answer:
Tertiary structures in proteins are formed due to the interaction of side chains via hydrophobic interactions, ionic bonding, hydrogen bonding, and disulfide linkages, as well as the folding of secondary structures like alpha-helices and beta-pleated sheets.
Step-by-step explanation:
The tertiary structure of proteins is crucial for their function, and it arises due to two primary reasons. First, the interaction of side chains (R-groups) from the primary amino acid sequence creates the complex three-dimensional shape. This involves a variety of chemical interactions such as hydrophobic interactions, ionic bonding, hydrogen bonding, and disulfide linkages. These forces act to stabilize the overall structure, which is essential for the protein's biological function. Second, the tertiary structure is influenced by the folding of secondary structures like α-helices and β-pleated sheets, which are themselves held together by hydrogen bonds. These secondary structures fold onto each other, further contributing to the overall three-dimensional conformation of the protein.