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nmdcat.online June 27, 2026

The critical event that leads to the denaturation of a protein by a heavy metal ion like lead (Pb²⁺) or mercury (Hg²⁺) is the

A. Hydrolysis of the protein's peptide backbone
B. Disruption of the hydrophobic core of the protein
C. Formation of strong bonds with sulfhydryl (-SH) groups of cysteine, altering the protein's structure
✓
D. Oxidation of the protein's carbon skeleton into CO2 and water

📝 Explanation

Heavy metals have high affinity for sulfur. They react with the thiol (-SH) groups of cysteine residues, forming mercaptides. This can block essential catalytic groups, disrupt disulfide bonds (if present), and severely distort the protein's tertiary and quaternary structure, leading to irreversible denaturation.

📖 Additional Information

  • Hydrolysis of the protein's peptide backbone
  • Disruption of the hydrophobic core of the protein
  • Formation of strong bonds with sulfhydryl (-SH) groups of cysteine, altering the protein's structure
  • Oxidation of the protein's carbon skeleton into CO2 and water

Heavy metals have high affinity for sulfur. They react with the thiol (-SH) groups of cysteine residues, forming mercaptides. This can block essential catalytic groups, disrupt disulfide bonds (if present), and severely distort the protein's tertiary and quaternary structure, leading to irreversible denaturation.

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