Tertiary structure is not directly dependent on . tertiary structure is not directly dependent on . bonds between sulfur atoms hydrophobic interactions hydrogen bonds ionic bonds peptide bonds
The correct answer and explanation is:
Correct Answer: Peptide bonds
Explanation (300 words):
The tertiary structure of a protein refers to the overall three-dimensional folding of a single polypeptide chain. This level of structure is stabilized by various interactions among the side chains (R groups) of amino acids. These interactions include:
- Hydrophobic interactions: Nonpolar side chains tend to avoid water and cluster together in the interior of the protein.
- Hydrogen bonds: Occur between polar side chains or between side chains and the backbone.
- Ionic bonds (salt bridges): Form between positively and negatively charged side chains.
- Disulfide bonds: Covalent bonds formed between sulfur atoms of cysteine residues.
All of these interactions and bonds contribute to maintaining the unique three-dimensional shape necessary for a protein’s function.
However, peptide bonds are not directly involved in determining the tertiary structure. Peptide bonds are covalent bonds that link amino acids together to form the primary structure of the protein — the linear sequence of amino acids. These bonds form between the amino group of one amino acid and the carboxyl group of another during a condensation reaction, resulting in the formation of a polypeptide chain.
While the sequence created by peptide bonds certainly affects what kinds of interactions can occur later (thereby influencing the final shape indirectly), peptide bonds themselves are not part of the interactions that stabilize tertiary structure. They are fixed structural connections that define the primary structure.
To summarize, tertiary structure arises from interactions among side chains, not from the peptide backbone. Therefore, peptide bonds are not directly responsible for the folding and stabilization that define the tertiary structure of a protein.
Thus, the correct answer is: Peptide bonds.