Final answer:
The sentence refers to the tertiary structure of a protein, which involves disulfide bonds that connect cysteine residues within a single polypeptide chain to stabilize its three-dimensional shape.
Step-by-step explanation:
The tertiary structure of a protein is what the sentence is referring to when mentioning disulfide bonds between cysteines that stabilize the protein's structure. Disulfide bonds are a form of covalent bond that is vital in maintaining the overall shape and functional integrity of a protein, particularly those formed from a single polypeptide chain. Disulfide bonds formed between cysteines play a key role in stabilizing the tertiary structure of the protein. Disulfide bonds are covalent bonds formed between sulfur atoms in the polypeptide chain. These bonds create strong linkages that help maintain the three-dimensional shape of the protein.
In the tertiary structure, amino acids far apart in the primary sequence can be brought together to form a compact, three-dimensional configuration. This is facilitated by interactions such as hydrogen bonding, ionic bonding, hydrophobic interactions, and in the case of cysteine residues, the formation of disulfide bridges. These interactions are crucial in shaping the protein into its functional form. While a protein's quaternary structure involves multiple polypeptide chains, the disulfide bond-stabilized structure mentioned in the sentence relates directly to a single polypeptide chain, hence it's part of the tertiary structure.