Selenium in the context of Direct current

A nutrient is a substance used by an organism to survive, grow and reproduce. The requirement for dietary nutrient intake applies to animals, plants, fungi and protists. Nutrients can be incorporated into cells for metabolic purposes or excreted by cells to create non-cellular structures such as hair, scales, feathers, or exoskeletons. Some nutrients can be metabolically converted into smaller molecules in the process of releasing energy such as for carbohydrates, lipids, proteins and fermentation products (ethanol or vinegar) leading to end-products of water and carbon dioxide. All organisms require water. Essential nutrients for animals are the energy sources, some of the amino acids that are combined to create proteins, a subset of fatty acids, vitamins and certain minerals. Plants require more diverse minerals absorbed through roots, plus carbon dioxide and oxygen absorbed through leaves. Fungi live on dead or living organic matter and meet nutrient needs from their host.

Different types of organisms have different essential nutrients. Ascorbic acid (vitamin C) is essential to humans and some animal species but most other animals and many plants are able to synthesize it. Nutrients may be organic or inorganic: organic compounds include most compounds containing carbon, while all other chemicals are inorganic. Inorganic nutrients include nutrients such as iron, selenium, and zinc, while organic nutrients include, protein, fats, sugars and vitamins.

In the context of nutrition, a mineral is a chemical element. Some "minerals" are essential for life, but most are not. Minerals are one of the four groups of essential nutrients; the others are vitamins, essential fatty acids, and essential amino acids. The five major minerals in the human body are calcium, phosphorus, potassium, sodium, and magnesium. The remaining minerals are called "trace elements". The generally accepted trace elements are iron, chlorine, cobalt, copper, zinc, manganese, molybdenum, iodine, selenium, and bromine; there is some evidence that there may be more.

The four organogenic elements, namely carbon, hydrogen, oxygen, and nitrogen (CHON), that comprise roughly 96% of the human body by weight, are usually not considered as minerals (nutrient). In fact, in nutrition, the term "mineral" refers more generally to all the other functional and structural elements found in living organisms.

The word metalloid comes from the Latin metallum ("metal") and the Greek oeidḗs ("resembling in form or appearance"). However, there is no standard definition of a metalloid and no complete agreement on which elements are metalloids. Despite the lack of specificity, the term remains in use in the literature.

The six commonly recognised metalloids are boron, silicon, germanium, arsenic, antimony and tellurium. Five elements are less frequently so classified: carbon, aluminium, selenium, polonium and astatine. On a standard periodic table, all eleven elements are in a diagonal region of the p-block extending from boron at the upper left to astatine at lower right. Some periodic tables include a dividing line between metals and nonmetals, and the metalloids may be found close to this line.

The chalcogens (/ˈkælkədʒənz/, KAL-kə-jənz) are the chemical elements in group 16 of the periodic table. This group is also known as the oxygen family. Group 16 consists of the elements oxygen (O), sulfur (S), selenium (Se), tellurium (Te), and the radioactive elements polonium (Po) and livermorium (Lv). Often, oxygen is treated separately from the other chalcogens, sometimes even excluded from the scope of the term "chalcogen" altogether, due to its very different chemical behavior from sulfur, selenium, tellurium, and polonium. The word "chalcogen" means "ore-forming"; chalcogens got their name because protoscientists and early scientists could discern that these essences (which science would later reveal to be chemical elements) were involved in ore formation.

Sulfur has been known since antiquity, and oxygen was recognized as an element in the 18th century. Selenium, tellurium and polonium were discovered in the 19th century, and livermorium in 2000. All of the chalcogens have six valence electrons, leaving them two electrons short of a full outer shell. Their most common oxidation states are −2, +2, +4, and +6. They have relatively small atomic radii, especially the lighter ones.

Organosulfur chemistry is the study of the properties and synthesis of organosulfur compounds, which are organic compounds that contain sulfur. They are often associated with foul odors, but many of the sweetest compounds known are organosulfur derivatives, e.g., saccharin. Nature abounds with organosulfur compounds—sulfur is vital for life. Of the 20 common amino acids, two (cysteine and methionine) are organosulfur compounds, and the antibiotics penicillin and sulfa drugs both contain sulfur. While sulfur-containing antibiotics save many lives, sulfur mustard is a deadly chemical warfare agent. Fossil fuels, coal, petroleum, and natural gas, which are derived from ancient organisms, necessarily contain organosulfur compounds, the removal of which is a major focus of oil refineries.

Sulfur shares the chalcogen group with oxygen, selenium, and tellurium, and it is expected that organosulfur compounds have similarities with carbon–oxygen, carbon–selenium, and carbon–tellurium compounds.

Balneotherapy (Latin: balneum "bath") is a method of treating diseases by bathing, a traditional medicine technique usually practiced at spas. Since ancient times, humans have used hot springs, public baths and thermal medicine for therapeutic effects. While it is considered distinct from hydrotherapy, there are some overlaps in practice and in underlying principles. Balneotherapy may involve hot or cold water, massage through moving water, relaxation, or stimulation. Many mineral waters at spas are rich in particular minerals such as silica, sulfur, selenium, and radium. Medicinal clays are also widely used, a practice known as 'fangotherapy'.

Tellurium is a chemical element; it has the symbol Te and atomic number 52. It is a brittle, mildly toxic, rare, silver-white metalloid. Tellurium is chemically related to selenium and sulfur, all three of which are chalcogens. It is occasionally found in its native form as elemental crystals. Tellurium is far more common in the universe as a whole than on Earth. Its extreme rarity in the Earth's crust, comparable to that of platinum, is due partly to its formation of a volatile hydride that caused tellurium to be lost to space as a gas during the hot nebular formation of Earth.

Tellurium-bearing compounds were first discovered in 1782 in a gold mine in Kleinschlatten, Transylvania (now Zlatna, Romania) by Austrian mineralogist Franz-Joseph Müller von Reichenstein, although it was Martin Heinrich Klaproth who named the new element in 1798 after the Latin tellus 'earth'. Gold telluride minerals are the most notable natural gold compounds. However, they are not a commercially significant source of tellurium itself, which is normally extracted as a by-product of copper and lead production.

Gold chalcogenides are compounds formed between gold and one of the chalcogens, elements from group 16 of the periodic table: oxygen, sulfur, selenium, or tellurium.

• Gold(III) oxide, Au₂O₃. Decomposes into gold and oxygen above 160 °C, and dissolves in concentrated alkalis to form solutions which probably contain the [Au(OH)₄] ion
• Gold(I) sulfide, Au₂S. Formed by reaction of hydrogen sulfide with gold(I) compounds.
• Gold(III) sulfide, Au₂S₃, claimed material but unsubstantiated.
• Gold tellurides: Au₂Te₃, Au₃Te₅, and AuTe₂ (approximate formulas) are known as non-stoichiometric compounds. They show metallic conductivity. Au₃Te₅ is a superconductor at 1.62 K.

Gold telluride minerals, such as calaverite and krennerite (AuTe₂), petzite (Ag₃AuTe₂), and sylvanite (AgAuTe₂), are minor ores of gold (and tellurium). See telluride minerals for more information.

Ostrich oil is an oil derived from the fat of ostriches. Ostrich oil is composed of 36.51% of saturated fat, 46.75% of monounsaturated fat, and 18.24% of polyunsaturated fat. Ostrich oil contains fatty acids, such as omega-3, omega-6, and omega-9. It also contains vitamins and minerals like vitamin E and selenium, which serve as natural antioxidants. Emu oil in the USA has a similar composition to ostrich oil, but ostrich oil has a higher omega-3 content, containing 2.1% compared to 0.25% in emu oil.

Ostrich oil has antibacterial properties, and is used for various skincare purposes, such as inflammation reduction. Due to the moisturizing properties, ostrich oil is currently used in cosmetic formulations and food chemistry. Ostrich oil is also used in the food industry as it has fatty acids and tocopherols, and a low cholesterol content.

Hydrolysate refers to any product of hydrolysis. Protein hydrolysate has special application in sports medicine because its consumption allows amino acids to be absorbed by the body more rapidly than intact proteins, thus maximizing nutrient delivery to muscle tissues. It is also used in the biotechnology industry as a supplement to cell cultures.In the December 2013 edition of The International Journal of Food Science and Technology, hydrolysate was shown to be rich in L-aspartic acid and the necessary minerals manganese and selenium

Thyroid hormones are two hormones produced and released by the thyroid gland, triiodothyronine (T₃) and thyroxine (T₄). They are tyrosine-based hormones that are primarily responsible for regulation of metabolism. T₃ and T₄ are partially composed of iodine, derived from food. A deficiency of iodine leads to decreased production of T₃ and T₄, enlarges the thyroid tissue and will cause the disease known as simple goitre.

The major form of thyroid hormone in the blood is thyroxine (T₄), whose half-life of around one week is longer than that of T₃. In humans, the ratio of T₄ to T₃ released into the blood is approximately 14:1. T₄ is converted to the active T₃ (three to four times more potent than T₄) within cells by deiodinases (5′-deiodinase). These are further processed by decarboxylation and deiodination to produce iodothyronamine (T₁a) and thyronamine (T₀a). All three isoforms of the deiodinases are selenium-containing enzymes, thus dietary selenium is essential for T₃ production. Calcitonin, a peptide hormone produced and secreted by the thyroid, is usually not included in the meaning of "thyroid hormone".

Organometallic chemistry is the study of organometallic compounds, chemical compounds containing at least one chemical bond between a carbon atom of an organic molecule and a metal, including alkali, alkaline earth, and transition metals, and sometimes broadened to include metalloids like boron, silicon, and selenium, as well. Aside from bonds to organyl fragments or molecules, bonds to 'inorganic' carbon, like carbon monoxide (metal carbonyls), cyanide, or carbide, are generally considered to be organometallic as well. Some related compounds such as transition metal hydrides and metal phosphine complexes are often included in discussions of organometallic compounds, though strictly speaking, they are not necessarily organometallic. The related but distinct term "metalorganic compound" refers to metal-containing compounds lacking direct metal-carbon bonds but which contain organic ligands. Metal β-diketonates, alkoxides, dialkylamides, and metal phosphine complexes are representative members of this class. The field of organometallic chemistry combines aspects of traditional inorganic and organic chemistry.

Organometallic compounds are widely used both stoichiometrically in research and industrial chemical reactions, as well as in the role of catalysts to increase the rates of such reactions (e.g., as in uses of homogeneous catalysis), where target molecules include polymers, pharmaceuticals, and many other types of practical products.

In chemistry, an octatomic element is an element that, at some standard temperature and pressure, is in a configuration of eight atoms bound together (a homonuclear molecule). The canonical example is sulfur, S₈, but red selenium is also an octatomic element stable at room temperature. Octaoxygen is also known, but it is extremely unstable.