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21 4. Content in the body and the biological role of d‑ elements: metal-containing enzymes. 5. Compounds of d ‑block elements as medicaments. 6. Medico-biological significance of elements of the p ‑block. 7. Compounds of elements of the p ‑block as medicines. Homework exercises. 1. Ba2+ ions are toxic to the body. Why is the radiopaque substance BaSO4 taken inside for X‑ray diagnostics of digestive tract diseases without fear? 2. The drugs NaHCO 3  or MgO are used under an increased acidity of gastric juice. What drug has a lesser side effect and why? 3. It is known that many soluble compounds of heavy metals (Ag, Hg, Cd, Ni, Zn, Cu) exert a toxic effect on living organisms. What is the basis for the toxic effect of these compounds? Explain the chemical mechanism of this process. 4. What substance – O 2  or CO – does form stronger coordination bond with the Fe  2+ ion of hemoglobin? 5. Explain, why the ion of Fe  2+ does not change the degree of oxidation during oxygenation (addition of an oxygen molecule)? 6. Which complex of platinum: trans - or cis -isomers of dichlorodiamine platinum (ΙΙΙ) has a therapeutic effect in case of oncological diseases? Explain the mechanism of that process. 7. What is the basis for the antiseptic effect of orthoboric acid and sodium tetraborate (borax)? Write an equation for the chemistry of the pharmacological action of the borax. 8. Aluminum phosphate AlPO 4  is poorly soluble in water. What is the significance of the formation of this phosphate in the body in life? 9. The chemical mechanism of the toxic effect of Pb  2+ ions are complicated. What reaction can you write to confirm the toxic effect of the ion on blood? 10. Nitrite ions causes oxygen deficiency in the blood. Write a chemical equation for this process. 11. Write the equations for the reactions of determining arsenic to biological material (Marsh’s test). 12. Sodium thiosulfate is used in medicine as a counter-toxic agent for poisoning by compounds oflead, mercury, cyanides. Write chemical equations for this process. 13. What reaction does take place on the skin’s surface in the treatment of scabies with a solution of sodium thiosulfate?