Biological active Alkaline earth metal ions

Role of alkaline earth metal ions in biological system

1. ROLE OF ALKALINE EARTH METAL IONS IN BIOLOGICAL SYSTEM VARINDER KHEPAR PhD CHEMISTRY

2. ELEMENTS IN OUR BODY Consider the content of the elements in the body of an average healthy person (weighing 70 kg). The content of the rest of metals does not exceed one gram particularly Cu –0.11 g and Mn – 0.02 g

3. DIETARY SOURCE OF CALCIUM Calcium is a critical element in all animals and human beings. A healthy human adult has about 1.05 kg Ca, of which 99% exists as phosphates resembling the mineral hydroxyapatite , Ca10(PO4)6(OH)2 , in bones and teeth. The primary dietary source of Ca is milk (65-76%), with smaller amounts derived from meat, fish and eggs (5-10%), and still less from non-dairy foods such as nuts, fruits, beans etc.

4. CALCIUM Ca 2+ ions play an important role in biological processes. Calcium also plays a significant role in skeletal formation. With phosphorus in the mineral hydroxyapatite C5 (PO4)3OH, it is the major constituent of bones, teeth and shells. In addition to skeletal role, Ca 2+ plays many biochemical roles such as: It acts as a messenger for hormonal action It acts as a trigger for muscular contraction It acts as initiation of blood clotting It also plays a role in the stabilization of protein structure It helps in the maintenance of rhythm of heart

5. CALCIUM PUMP Ca 2+ plays an important role in muscles. It triggers a signal that stimulates muscles to contract. In the normal state, the concentration in the intracellular fluids is very low. Their concentration in intra cellular fluids is about 10,000 times less than their concentration in the extracellular fluids. The maintenance of low calcium concentration in the intra cellular fluids is done by biochemical process called as calcium pump. Concentration: Outside of Cell [Ca 2+ ] = 0.001 M Inside Cell [Ca 2+ ] = 10 -7 M Ca 2+ - ATPase in Cell Membrane controls concentration

6. ROLE OF Ca 2+ IN TRANSPORT The nerve pulses include the SR( sarcoplasmic reticulum) membrane quickly release the large amount of Ca 2+ which trigger muscle contraction. Therefore, Ca+ ions act as intermediary between the nerve impulse and muscle contraction. Relaxation of the muscle requires that Ca concentration be reduced to their resting levels. This is accompanied by ATP driven Ca 2+ transport protein called Ca + - ATPase .

7. Just like Na + -K + - ATPase is the integral part of N + -K + pump, similarly, Ca 2+ - ATPase is also an integral part of Ca 2+ pump. The phosphorylation by Ca 2+ and dephosphorylation by Mg 2+ completes the cycle. During the cycle two Ca 2+ are transported for each ATP hydrolysed. The very high affinity of At Pase for Ca 2+ helps it to effectively transport Ca 2+ from cytosol (where [Cu2+]<10-5 M) into sarcoplasmic reticulum, SR (where [Ca2+] about 10-2 M)

8. DEFICIENCY In case of excess Ca 2+ , it comes in to the blood as ca is rejected by cell and its salts are not soluble. So excess of calcium leads to the formation of stones ( due to calcium oxalate, rich in tomatoes ), hardening of arteries, and cataracts in the eye. The decrease of Ca 2+ content in blood due to dietary deficiency or from an insufficiency of parathyroid hormone may lead to a disease called tetany and weakens the bones.

9. MAGNESIUM Magnesium, an abundant element in the earth’s crust, is vital to both plant and animal life. Chlorophyll pigment in plants is a Mg- porphyrin complex All enzymatic reaction in animals that are catalyzed by ATP (Adenosine Triphosphate ) require Mg as a cofactor. Oxidative phosphorylation , DNA transcription, RNA function, protein synthesis and critical cell membrane functions are all dependent upon optimal Mg concentrations. An average human being holds about 35g of Mg, of which approximately 99% is either intracellular or it is present in bones.

10. DIETARY SOURCES OF Mg High Mg Dietary sources include green leaves, nuts, sea foods and vegetables. Meat has intermediate Mg content. Deficiency of Mg causes convulsions and excess causes anaesthetic feeling.

11. BIOLOGICAL ROLE OF Mg 2+ Mg 2+  is the fourth-most-abundant metal  ion in cells Chlorophyll In photosynthetic organisms, Mg 2+  has the additional vital role of being the coordinating ion in the chlorophyll molecule. This role was discovered by Richard Willstätter , who received the Nobel Prize in Chemistry 1915 for the purification and structure of chlorophyll binding with six number of carbon.

12. Enzymes Mg 2+  interacts with substrates, enzymes as part of the active site. Mg 2+  interacts with substrates through inner sphere coordination, stabilises the anions or reactive intermediates, and bind to ATP and activate the molecule to nucleophilic attack . ATP (adenosine triphosphate ), the main source of energy in cells, must be bound to a magnesium ion in order to be biologically active.

13. Nucleic acids Nucleic acids have an important range of interactions with Mg 2 + The binding of Mg 2+  to DNA and RNA  stabilises structure Ribosomes  contain large amounts of Mg 2+  and provide the stabilisation to the complex of ribo -protein

14. BARIUM Barium has no biological role. The British Pharmaceutical Codex from 1907 indicates that barium chloride [" barii chloridum ", BaCl 2 . 2H 2 O] has a stimulant action on the heart and other muscles. Barium   sulphide ( BaS ) was used as a depilatory agent (removes hair).

15. Barium enema : Barium is a white, ‘radio-opaque’ powder that is visible with x-rays. It is used to demonstrate the structure and the function of the organs that make up the digestive tract, such as the stomach, small bowel and large bowel. A liquid that contains barium (a silver-white metallic compound) is put into the rectum. The barium coats the large bowel and X-rays are taken. This test may show what part of the bowel is blocked.

16. BARIUM MEAL You will be asked to drink the barium so the radiologist can observe your swallowing and evaluate the structure of your oesophagus . During a barium meal you will be asked to drink a mixture that is fizzy, or two substances. These drinks contain ingredients that cause gas to be produced, which expands your stomach and the duodenum. When the gas is combined with the barium it creates a coating on the inside of your stomach and allows the radiologist to evaluate the stomach lining. Many people feel the urge to burp during this part of the examination.

17. BERYLLIUM   Beryllium has no known biological role, and its dust causes chronic inflammation of the lungs and shortage of breath. Brief exposure to a lot of beryllium, or long exposure to a little, will bring lung condition which is known as berylliosis .

18. STRONTIUM In biological systems, calcium is substituted to a small extent by strontium . In the human body, most of the absorbed strontium is deposited in the bones. The ratio of strontium to calcium in human bones is between 1:1000 and 1:2000, roughly in the same range as in the blood serum . The average human has an intake of about two milligrams of strontium a day

19. But strontium ranelate also increases the risk of serious cardiovascular disorders S trontium has been shown to inhibit sensory irritation when applied topically to the skin Those with a personal or family history of blood clotting disorders are advised to avoid strontium

20. RADIUM Radium has no known biological role. It is toxic due to its radioactivity.  Radium  is present in all uranium ores, and could be extracted as a by-product of uranium  refining. Radium-223 is sometimes used to treat prostate cancer that has spread to the bones. Because bones contain calcium and radium is in the same group as calcium, it can be used to target cancerous bone cells. It gives off alpha particles that can kill the cancerous cells. Radium used to be used in luminous paints, for example in clock and watch dials. Although the alpha rays could not pass through the glass or metal of the watch casing, it is now considered to be too hazardous to be used in this way.

21. COLOUR ON FLAME

22. REFRENCES https://epathshala.nic.in https://en.wikipedia.org/wiki/Calcium_in_biology https://en.wikipedia.org/wiki/Magnesium_in_biology Jauhar S P (2016) Inorganic chemistry. Modern publishers, Pp 146-82. https://courses.lumenlearning.com