Which functional group is involved in the formation of disulfide bridges in proteins?

• A. Amino (–NH_2)
• B. Thiol (–SH)
• C. Carboxyl (–COOH)
• D. Hydroxyl (–OH)

Answer: (B)

Verified step by step guidance

1. Understand the context: Disulfide bridges are covalent bonds that stabilize the tertiary and quaternary structure of proteins. These bonds are formed between specific functional groups in amino acids.
2. Identify the amino acid responsible: The thiol group (–SH) is found in the side chain of the amino acid cysteine. This group is crucial for forming disulfide bridges.
3. Explain the chemical reaction: Two thiol groups from cysteine residues undergo oxidation to form a disulfide bond (–S–S–). This reaction involves the removal of hydrogen atoms from the thiol groups.
4. Compare functional groups: Amino (–NH_2), carboxyl (–COOH), and hydroxyl (–OH) groups do not participate in disulfide bridge formation. Only the thiol group (–SH) has the chemical properties required for this reaction.
5. Conclude: The functional group involved in the formation of disulfide bridges in proteins is the thiol group (–SH), specifically from cysteine residues.