selenium as a element

8/8/2019 Selenium as a Element

http://slidepdf.com/reader/full/selenium-as-a-element 1/16



Selenium as a elementy Chemical element with atomic number 34,atomic mass

78.96.y It is non metal chemically related to sulfur and tellurium

and rarely occurs in it element state.y In its stable form the selenium is dense purpulish grey in

color .y Structurally trigonal polymer chain steep rhombohedrons

crystals.y Trace amount is necessary for cellular function , seleniumsalts are toxic in large amounts.

y Toxic for humans working in coal industry.



HI STORY

y In 1817 the selenium is discovered by JONS JAKOB BERZELIUS.He found the element associated with Telliurium obtained in aproduct of sulfuric acid production.

y Because of the toxic feature in large amounts for humans andanimals. It was recognized as an important veternary toxin.y Later in 1954, it was identified that the presence of selenium had

a Specific biological functions in micro organisms.y In 1957, Essentiality for mammalian life was discovered.y In 1970s, it was shown to be present in two independent sets of

enzymes.y During 1980s, it was discovered that selenocystine presence in

proteins.



OCCURRENCEy Selenium occurs naturally in organic forms such as

selenide, selenate and selenite.y In soil selenium most oftenly occurs in soluble formsuch as selenate(analogous to sulfate) which are

leached into rivers easily by runoff.



NATURAL FOOD SOURCE OFSELENIUM

Natural food sources high in selenium includey cereals(e.g.. corn, wheat and rice)y nuts(Brazil nuts, walnuts)y legumes(soya bean)y Animal products-Beef, chicken, egg, cheese.y Sea food-Tuna.y And other sources are oats, cods and turkey.



B IOCH EMICAL ROLE OF SELENIUMIN ANIMALSy Selenium is an essential micro nutrients for animals

and component of the unusual amino acidsselenocysteine, selenomethionine.y In humans it functions as co-factor for reduction of

antioxidant enzyme such as gluctathione peroxidases

and certain forms of thioredoxin reductase.



B IOCH EMICAL ROLE OF SELENIUMIN PLANTSy It occurs as a bystander mineral.y Sometimes in toxic preparations in forage i.e., some plants

may accumulate selenium as a defense against being eatenby animals.y Some plants like LOCOWEED which need selenium which

are used as indicator for selenium presence in soil.HIG H LEVEL Se INDICATOR

Astragalus species.Prince s plume (Stanlya spp..) Woody asters (Xylorhiza spp..)False golden weed (Oonopsis spp..)



DEFICIENCY DISEASES OF

SELENIUMKESHAN DISEASEKASHIN-BECK DISEASE

MYXEDEMATOUS ENDEMIC CRETINISM



KESH AN DISEASEy

It was identified in the year 1935 .y The most susceptible were young

and middle aged women.y It occurred in hilly and

mountainous regions wherethere is low soil salinization.

y Morphological changes Heart isthe main target organ, deficiency causes necrosis of myocardium.

y Membrane structure such asmitochondria or Sarcolemma areaffected earlier than otherorganelles.



KASHI N-B ECK DISEASE

y Identified by Kashin (1859-1860)Beck(1899-1906).

y This is an endemic disease which shows degeneration andnecrosis of cartilage tissues.

y CLINICAL MANIFESTATION-Fatigue, joints stiffness,limitation of flexion of fingers .



MYXEDEMATOUS ENDEMIC

CRETINISMy It shows Mental Retardation

along with muscle pain, weakness, loss of pigment inhair and skin, and whiteningof the nail beds.



TOXICITY OF SELENIUMy Although Se is an eventually trace element, it is toxic if taken in

excess. Exceeding the tolerable upper intake level of 400micrograms per day can lead to selenosis.

SYMPTOMS OF SELENOSISG arlic odor on the breathG astro intestinal disordersHair loss Whitening of nailsFatigueIrritability Neurological damageExtreme cases Cirrhosis of liver, Pulmonary edena and death



P REVENTION OF SELENIUM

DEFFIICIENCYy Purify drinking water by filtration.y Diversification of food habits in variety and source.y Exchange of staple grains among different areas.y Intake of soya beans and animal foods to get more Se,

Vitamin E, Methionine and other nutrients.y Oral administration of Sodium Selenite tablet 20 40

micrograms.



CONCLUSIONy It is present in protein Selenoprotein.y Major role of Selenium is to maintain glutathione

peroxidase activity.y Selenium deficiency or toxicity depends on the

concentration of Selenium present in soil or water or foods.y Selenium deficiency causes Keshan and Kashin Beck

disease in humans.y

Toxicity of Selenium causes loss of hair, skin lesions andabnormalities of Nervous system.y Oral Administration of sodium selenite tablet will prevent

Selenium deficiency.



TH ANK YOU

selenium as a element

Documents