Question

Why do heavy metals, like Hg2+ and Pb2+, cause poisoning? How does an antidote, like milk or raw egg white, work?

Answer 1

Heavy metal ions cause poisoning as they dissolve in blood and transfered to different organs, where they accumulate and show strong affinity towards Sulfur found in protein (Enzymes).By reacting with sulfhydral groups present in enzymes, they deactivate/denature them and can alter the metabolic processes.

Heavy metal salts act to denature proteins in much the same manner as acids and bases. Since salts are ionic they disrupt salt bridges in proteins. The reaction of a heavy metal salt with a protein usually leads to an insoluble metal protein salt. This same reaction is used in reverse in cases of acute heavy metal poisoning. In such a situation, a person may have swallowed a significant quantity of a heavy metal salt. As an antidote, a protein such as milk or egg whites may be administered to precipitate the poisonous salt. Then an emetic is given to induce vomiting so that the precipitated metal protein is discharged from the body.