Biochemistry

Nickel. Its content in the Earth's crust is 5.8-10 ’ 3 % by weight. Nickel and its compounds are highly toxic. The toxic dose of nickel for rats is 50 mg. Volatile nickel compounds, in particular, its tetracarbonyl Ni(CO) 4 , which is three times more toxic than CO (carbon monoxide), are especially harmful. General nickel poisoning is manifested in salivation, vomiting, convulsions. Nickel is able to lower the content of ascorbic acid (vitamin C) in the body. There is an assumption about the carcinogenic properties of this element. Wearing watches andjewelry containing nickel can cause skin damage - nickel dermatitis. Lithium. In the Earth's crust it contains 3.2- 10 ’ 3 % of the total mass. In the animal and human body, lithium is concentrated in the liver, kidneys, and blood plasma. The physiological role of lithium is associated with its effect on the breakdown of carbohydrates. The inhibitory effect of lithium on thyroid function was also noted. Lithium deficiency in animals leads to an increase in blood cholesterol. The toxic effect of lithium on the human body was discovered. Its excess can cause a violation of the excretory function of the kidneys and cardiac activity, this is accompanied by a drop in blood pressure, and in severe cases a coma. Other chemical elements with high biological activity Some chemical elements are quite regularly found in biological environments, but our knowledge is still insufficient to judge their physiological role with confidence. They deserve attention, since a lot of experimental data has been accumulated on the biological activity of these elements, in particular, on their effect on human and animal health. Arsenic is a rare element in the Earth's crust (1.7- IO" 4 % by weight). In biological media As is present in ultramicroscopic amounts. Ail arsenic compounds are poisonous to humans and animals, especially white arsenic, or arsenic anhydride As 2 O 3 , which causes fatal poisoning at a dose of 60-70 mg. The physiological activity of As is due to its ability to chemically bind to sulfhydryl groups (-SH), which are part of amino acids and proteins. This interaction leads to a violation (blocking) of a number of biochemical processes, which underlies poisoning by arsenic and other heavy metals (mercury, lead, antimony, etc.), called thiol poisons. Acute arsenic poisoning usually occurs when toxic doses of As 2 O 3 are ingested. Symptoms of poisoning - nausea, vomiting, impaired function of the peripheral and central nervous system, in severe cases, there is a violation of blood circulation, which ends in death. Arsenic compounds can be fixed for a long time in bones, liver, hair, and skin. 19