Final answer:
The hydrophobic effect is the primary driving force behind the tertiary structure of proteins, along with stabilizing interactions such as ionic and hydrogen bonding, and disulfide linkages.
Step-by-step explanation:
The driving force to which globular proteins adopt and maintain their tertiary structure is primarily the hydrophobic effect. However, tertiary protein structure is stabilized by several interactions, according to figures 7.21, 16.5.5, 19.6.5, 18.8.2, and 19.5.5. These interactions include ionic bonding, hydrogen bonding, disulfide linkages, and dispersion forces. The hydrophobic effect is crucial as hydrophobic amino acid side chains tend to aggregate away from water, which contributes significantly to the folding of the protein into its functional 3D shape. The other interactions further stabilize the structure. Ionic bonds occur between differentially charged amino acid side chains, hydrogen bonds occur between electronegative atoms like oxygen or nitrogen and a hydrogen atom, and disulfide linkages form between the sulfur atoms of two cysteine amino acids through an oxidation reaction.