Final answer:
Disulfide bonds are strong covalent linkages formed between sulfur atoms of two cysteine side chains within proteins, playing a critical role in maintaining the protein's tertiary structure and integrity.
Step-by-step explanation:
The question addresses the disulfide bonds that are formed in proteins, which are essential for the stability and structure of these biomolecules. Disulfide bonds are strong chemical side bonds that occur when the sulfur atoms in the sulfhydryl (-SH) groups of two cysteine amino acids within a protein are joined through an oxidation reaction. This process forms a covalent linkage known as a disulfide bridge or disulfide linkage (-S-S-), stabilizing the protein's tertiary structure. The formation of cystine from two cysteine molecules is a good example of such a bond. The sulfur-containing amino acids, cysteine, and methionine, play important roles in establishing these covalent bonds, which are crucial for protein integrity and function. Disulfide linkages are not only involved in the intrachain (within the same polypeptide) bonding but also in interchain (between different polypeptides) interactions, such as in the assembly of insulin molecules.
This biochemical phenomenon is exemplified in everyday life, such as when heat from a hair straightener breaks the disulfide bonds in hair, temporarily changing its shape.