Answer:
Tertiary protein structure results mainly from various interactions and bonds between the side chains (R groups) of the amino acids that make up the protein. The primary interactions and bonds that contribute to tertiary structure include:
Hydrogen bonds: These occur between polar side chains and contribute significantly to the stability of the protein's tertiary structure.
Ionic bonds (salt bridges): These are formed between positively and negatively charged side chains.
Hydrophobic interactions: Nonpolar side chains tend to cluster together in the interior of the protein, away from the aqueous environment, which helps stabilize the protein structure.
Disulfide bonds (disulfide bridges): These are covalent bonds that form between the sulfur atoms of cysteine residues, creating strong links that stabilize the protein's structure.
Van der Waals forces: These are weak, non-specific interactions between nonpolar side chains that contribute to the overall stability of the protein.
Among these interactions, disulfide bonds are particularly strong covalent bonds, while the other interactions are non-covalent but collectively provide significant stability to the protein's tertiary structure.