1.
Melamine
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Melamine /ˈmɛləmiːn/ is an organic base and a trimer of cyanamide, with a 1,3, 5-triazine skeleton. Melamine is also a metabolite of cyromazine, a pesticide and it is formed in the body of mammals that have ingested cyromazine. It has been reported that cyromazine can also be converted to melamine in plants, the German word melamin was coined by combining the words, melam and amine. Melamine is, therefore, unrelated etymologically to the root melas, from which the words melanin, a pigment, and melatonin, Melamine foam is used as insulation, soundproofing material and in polymeric cleaning products, such as Magic Eraser. Melamine is one of the components in Pigment Yellow 150. Melamine also enters the fabrication of melamine poly-sulfonate used as superplasticizer for making high-resistance concrete and it results in concrete with a lower porosity and a higher mechanical strength, exhibiting an improved resistance to aggressive environments and a longer lifetime. The use of melamine as fertilizer for crops had been envisaged during the 1950s and 1960s because of its high nitrogen content, however, melamine is much more expensive to produce than are other common nitrogen fertilizers, such as urea. To be effective as a fertilizer, it is essential that the plant nutrients are released or made available in a manner that matches the needs of the growing crop. The nitrogen mineralization process for melamine is extremely slow, making this product both economically and scientifically impractical for use as a fertilizer, Melamine and its salts are used as fire-retardant additives in paints, plastics, and paper. Melamine derivatives of arsenical drugs are potentially important in the treatment of African trypanosomiasis, Melamine use as non-protein nitrogen for cattle was described in a 1958 patent. Melamine is sometimes added to food products in order to increase the apparent protein content. Standard tests, such as the Kjeldahl and Dumas tests, estimate protein levels by measuring the nitrogen content, an instrument developed by the company CEM Corp allows the determination of protein content directly in some applications, the instrument cannot be fooled by adding melamine in the sample. Melamine is also used as a nitrogen and carbon source for N-doped carbon nanotube, n-CNTs can be prepared via Chemical Vapor Deposition method by pyrolysizing melamine under an Ar atmosphere in a horizontal glass tube. A thin film of iron is first deposited on a Si/SiO2 wafer, n-CNT synthesis occurs at a furnace temperatures between 800 and 980 °C. Melamine is described as Harmful if swallowed, inhaled or absorbed through the skin, chronic exposure may cause cancer or reproductive damage. However, the lethal dose is on a par with common table salt with an LD50 of more than 3 grams per kilogram of bodyweight. The European Union set a standard for human consumption of melamine at 0.2 mg per kg of body mass, Canada declared a limit of 0.35 mg. The World Health Organizations food safety director estimated that the amount of melamine a person could stand per day without incurring a bigger health risk, toxicity of melamine can be mediated by intestinal microbes
2.
Melatonin
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Melatonin, also known as N-acetyl-5-methoxy tryptamine, is a hormone that is produced by the pineal gland in animals and regulates sleep and wakefulness. Melatonin is also produced in plants where it functions as a first line of defense against oxidative stress, in animals, melatonin is involved in the entrainment of the circadian rhythms including sleep-wake timing, blood pressure regulation, seasonal reproduction, and many others. As a medicine, it is used for the treatment of insomnia, however, Melatonin is sold over the counter in the United States and Canada. In other countries, it may require a prescription or it may be unavailable, Melatonin has shown promise in treating sleep-wake cycle disorders in children with underlying neurodevelopment difficulties. As add-on to antihypertensive therapy, prolonged-release melatonin has improved blood pressure control in people with nocturnal hypertension, people with circadian rhythm sleep disorders may use oral melatonin to help entrain to the environmental light-dark cycle. Melatonin reduces sleep onset latency to an extent in people with delayed sleep phase disorder than in people with insomnia. Melatonin has been studied for insomnia in the elderly, prolonged-release melatonin has shown good results in treating insomnia in older adults. Short-term treatment of prolonged-release melatonin was found to be effective and safe in improving sleep latency, sleep quality, evidence for use of melatonin as a treatment for insomnia is, as of 2015, insufficient, low-quality evidence indicates it may speed the onset of sleep by 6 minutes. A later review found evidence for efficacy in shift work. Melatonin is known to aid in reducing the effects of jet lag, especially in eastward travel, if the timing is not correct, however, it can instead delay adaption. Melatonin appears also to have limited use against the problems of people who work rotating or night shifts. Tentative evidence shows melatonin may help reduce some types of headaches including cluster headaches, a 2013 review by the National Cancer Institutes found evidence for use to be inconclusive. A2005 review of unblinded clinical trials found a rate of death. Both animal and human studies have shown melatonin to protect against radiation-induced cellular damage, Melatonin and its metabolites protect organisms from oxidative stress by scavenging reactive oxygen species which are generated during exposure. Melatonin has been described as a protective, readily available. Tentative evidence of benefit exists for treating tinnitus, Melatonin might improve sleep in autistic people. Children with autism have abnormal melatonin pathways and below-average physiological levels of melatonin, Melatonin supplementation has been shown to improve sleep duration, sleep onset latency, and night-time awakenings. However, many studies on melatonin and autism rely on self-reported levels of improvement, however, larger and longer studies are needed to establish long-term safety and optimal dosing
3.
Greek language
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Greek is an independent branch of the Indo-European family of languages, native to Greece and other parts of the Eastern Mediterranean. It has the longest documented history of any living language, spanning 34 centuries of written records and its writing system has been the Greek alphabet for the major part of its history, other systems, such as Linear B and the Cypriot syllabary, were used previously. The alphabet arose from the Phoenician script and was in turn the basis of the Latin, Cyrillic, Armenian, Coptic, Gothic and many other writing systems. Together with the Latin texts and traditions of the Roman world, during antiquity, Greek was a widely spoken lingua franca in the Mediterranean world and many places beyond. It would eventually become the official parlance of the Byzantine Empire, the language is spoken by at least 13.2 million people today in Greece, Cyprus, Italy, Albania, Turkey, and the Greek diaspora. Greek roots are used to coin new words for other languages, Greek. Greek has been spoken in the Balkan peninsula since around the 3rd millennium BC, the earliest written evidence is a Linear B clay tablet found in Messenia that dates to between 1450 and 1350 BC, making Greek the worlds oldest recorded living language. Among the Indo-European languages, its date of earliest written attestation is matched only by the now extinct Anatolian languages, the Greek language is conventionally divided into the following periods, Proto-Greek, the unrecorded but assumed last ancestor of all known varieties of Greek. The unity of Proto-Greek would have ended as Hellenic migrants entered the Greek peninsula sometime in the Neolithic era or the Bronze Age, Mycenaean Greek, the language of the Mycenaean civilisation. It is recorded in the Linear B script on tablets dating from the 15th century BC onwards, Ancient Greek, in its various dialects, the language of the Archaic and Classical periods of the ancient Greek civilisation. It was widely known throughout the Roman Empire, after the Roman conquest of Greece, an unofficial bilingualism of Greek and Latin was established in the city of Rome and Koine Greek became a first or second language in the Roman Empire. The origin of Christianity can also be traced through Koine Greek, Medieval Greek, also known as Byzantine Greek, the continuation of Koine Greek in Byzantine Greece, up to the demise of the Byzantine Empire in the 15th century. Much of the written Greek that was used as the language of the Byzantine Empire was an eclectic middle-ground variety based on the tradition of written Koine. Modern Greek, Stemming from Medieval Greek, Modern Greek usages can be traced in the Byzantine period and it is the language used by the modern Greeks, and, apart from Standard Modern Greek, there are several dialects of it. In the modern era, the Greek language entered a state of diglossia, the historical unity and continuing identity between the various stages of the Greek language is often emphasised. Greek speakers today still tend to regard literary works of ancient Greek as part of their own rather than a foreign language and it is also often stated that the historical changes have been relatively slight compared with some other languages. According to one estimation, Homeric Greek is probably closer to demotic than 12-century Middle English is to modern spoken English, Greek is spoken by about 13 million people, mainly in Greece, Albania and Cyprus, but also worldwide by the large Greek diaspora. Greek is the language of Greece, where it is spoken by almost the entire population
4.
Pigment
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A pigment is a material that changes the color of reflected or transmitted light as the result of wavelength-selective absorption. This physical process differs from fluorescence, phosphorescence, and other forms of luminescence, many materials selectively absorb certain wavelengths of light. Materials that humans have chosen and developed for use as pigments usually have properties that make them ideal for coloring other materials. A pigment must have a high tinting strength relative to the materials it colors and it must be stable in solid form at ambient temperatures. For industrial applications, as well as in the arts, permanence, pigments that are not permanent are called fugitive. Fugitive pigments fade over time, or with exposure to light, pigments are used for coloring paint, ink, plastic, fabric, cosmetics, food, and other materials. Most pigments used in manufacturing and the arts are dry colorants. This powder is added to a binder, a neutral or colorless material that suspends the pigment. A distinction is made between a pigment, which is insoluble in its vehicle, and a dye, which either is itself a liquid or is soluble in its vehicle. A colorant can act as either a pigment or a dye depending on the vehicle involved, in some cases, a pigment can be manufactured from a dye by precipitating a soluble dye with a metallic salt. The resulting pigment is called a lake pigment, the term biological pigment is used for all colored substances independent of their solubility. In 2006, around 7.4 million tons of inorganic, organic, asia has the highest rate on a quantity basis followed by Europe and North America. By 2020, revenues will have risen to approx, the global demand on pigments was roughly US$20.5 billion in 2009, around 1. 5-2% up from the previous year. It is predicted to increase in a growth rate in the coming years. The worldwide sales are said to increase up to US$24.5 billion in 2015, pigments appear the colors they are because they selectively reflect and absorb certain wavelengths of visible light. White light is an equal mixture of the entire spectrum of visible light with a wavelength in a range from about 375 or 400 nanometers to about 760 or 780 nm. When this light encounters a pigment, parts of the spectrum are absorbed by the molecules or ions of the pigment, in organic pigments such as diazo or phthalocyanine compounds the light is absorbed by the conjugated systems of double bonds in the molecule. Some of the inorganic pigments such as vermilion or cadmium yellow absorb light by transferring an electron from the ion to the positive ion
5.
Organism
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In biology, an organism is any contiguous living system, such as an animal, plant, fungus, protist, archaeon, or bacterium. All known types of organisms are capable of some degree of response to stimuli, reproduction, growth and development and homeostasis. An organism consists of one or more cells, when it has one cell it is known as an organism. Most unicellular organisms are of microscopic scale and are thus described as microorganisms. Humans are multicellular organisms composed of trillions of cells grouped into specialized tissues. An organism may be either a prokaryote or a eukaryote, prokaryotes are represented by two separate domains—bacteria and archaea. Eukaryotic organisms are characterized by the presence of a cell nucleus. Fungi, animals and plants are examples of kingdoms of organisms within the eukaryotes, estimates on the number of Earths current species range from 10 million to 14 million, of which only about 1.2 million have been documented. More than 99% of all species, amounting to five billion species. In 2016, a set of 355 genes from the last universal ancestor of all living organisms living was identified. The term organism first appeared in the English language in 1703 and it is directly related to the term organization. There is a tradition of defining organisms as self-organizing beings. An organism may be defined as an assembly of molecules functioning as a more or less stable whole that exhibits the properties of life. Dictionary definitions can be broad, using such as any living structure, such as a plant, animal, fungus or bacterium, capable of growth. Many definitions exclude viruses and possible man-made non-organic life forms, as viruses are dependent on the machinery of a host cell for reproduction. A superorganism is an organism consisting of individuals working together as a single functional or social unit. There has been controversy about the best way to define the organism, several contributions are responses to the suggestion that the category of organism may well not be adequate in biology. Viruses are not typically considered to be organisms because they are incapable of autonomous reproduction and this controversy is problematic because some cellular organisms are also incapable of independent survival and live as obligatory intracellular parasites
6.
Redox
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Redox is a chemical reaction in which the oxidation states of atoms are changed. Any such reaction involves both a process and a complementary oxidation process, two key concepts involved with electron transfer processes. Redox reactions include all chemical reactions in which atoms have their oxidation state changed, in general, the chemical species from which the electron is stripped is said to have been oxidized, while the chemical species to which the electron is added is said to have been reduced. It can be explained in terms, Oxidation is the loss of electrons or an increase in oxidation state by a molecule, atom. Reduction is the gain of electrons or a decrease in state by a molecule, atom. As an example, during the combustion of wood, oxygen from the air is reduced, the reaction can occur relatively slowly, as in the case of rust, or more quickly, as in the case of fire. Redox is a portmanteau of reduction and oxidation, the word oxidation originally implied reaction with oxygen to form an oxide, since dioxygen was historically the first recognized oxidizing agent. Later, the term was expanded to encompass oxygen-like substances that accomplished parallel chemical reactions, ultimately, the meaning was generalized to include all processes involving loss of electrons. The word reduction originally referred to the loss in weight upon heating a metallic ore such as an oxide to extract the metal. In other words, ore was reduced to metal, antoine Lavoisier showed that this loss of weight was due to the loss of oxygen as a gas. Later, scientists realized that the atom gains electrons in this process. The meaning of reduction then became generalized to all processes involving gain of electrons. Even though reduction seems counter-intuitive when speaking of the gain of electrons, it help to think of reduction as the loss of oxygen. Since electrons are charged, it is also helpful to think of this as reduction in electrical charge. The electrochemist John Bockris has used the words electronation and deelectronation to describe reduction and oxidation processes respectively when they occur at electrodes and these words are analogous to protonation and deprotonation, but they have not been widely adopted by chemists. The term hydrogenation could be used instead of reduction, since hydrogen is the agent in a large number of reactions. But, unlike oxidation, which has been generalized beyond its root element, the word redox was first used in 1928. The processes of oxidation and reduction occur simultaneously and cannot happen independently of one another, the oxidation alone and the reduction alone are each called a half-reaction, because two half-reactions always occur together to form a whole reaction
7.
Amino acid
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Amino acids are organic compounds containing amine and carboxyl functional groups, along with a side chain specific to each amino acid. The key elements of an acid are carbon, hydrogen, oxygen. About 500 amino acids are known and can be classified in many ways, in the form of proteins, amino acids comprise the second-largest component of human muscles, cells and other tissues. Outside proteins, amino acids perform critical roles in such as neurotransmitter transport. In biochemistry, amino acids having both the amine and the acid groups attached to the first carbon atom have particular importance. They are known as 2-, alpha-, or α-amino acids and they include the 22 proteinogenic amino acids, which combine into peptide chains to form the building-blocks of a vast array of proteins. These are all L-stereoisomers, although a few D-amino acids occur in bacterial envelopes, as a neuromodulator, twenty of the proteinogenic amino acids are encoded directly by triplet codons in the genetic code and are known as standard amino acids. The other two are selenocysteine, and pyrrolysine, pyrrolysine and selenocysteine are encoded via variant codons, for example, selenocysteine is encoded by stop codon and SECIS element. N-formylmethionine is generally considered as a form of methionine rather than as a separate proteinogenic amino acid, codon–tRNA combinations not found in nature can also be used to expand the genetic code and create novel proteins known as alloproteins incorporating non-proteinogenic amino acids. Many important proteinogenic and non-proteinogenic amino acids also play critical roles within the body. Nine proteinogenic amino acids are called essential for humans because they cannot be created from other compounds by the human body, others may be conditionally essential for certain ages or medical conditions. Essential amino acids may also differ between species, because of their biological significance, amino acids are important in nutrition and are commonly used in nutritional supplements, fertilizers, and food technology. Industrial uses include the production of drugs, biodegradable plastics, the first few amino acids were discovered in the early 19th century. In 1806, French chemists Louis-Nicolas Vauquelin and Pierre Jean Robiquet isolated a compound in asparagus that was subsequently named asparagine, cystine was discovered in 1810, although its monomer, cysteine, remained undiscovered until 1884. Glycine and leucine were discovered in 1820, usage of the term amino acid in the English language is from 1898. Proteins were found to yield amino acids after enzymatic digestion or acid hydrolysis, in the structure shown at the top of the page, R represents a side chain specific to each amino acid. The carbon atom next to the group is called the α–carbon. Amino acids containing an amino group bonded directly to the alpha carbon are referred to as amino acids
8.
Tyrosine
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Tyrosine or 4-hydroxyphenylalanine is one of the 20 standard amino acids that are used by cells to synthesize proteins. It is an amino acid with a polar side group. Its codons are UAC and UAU, the word tyrosine is from the Greek tyros, meaning cheese, as it was first discovered in 1846 by German chemist Justus von Liebig in the protein casein from cheese. It is called tyrosyl when referred to as a group or side chain. Aside from being an amino acid, tyrosine has a special role by virtue of the phenol functionality. It occurs in proteins that are part of signal transduction processes and it functions as a receiver of phosphate groups that are transferred by way of protein kinases. Phosphorylation of the group changes the activity of the target protein. A tyrosine residue plays a important role in photosynthesis. In chloroplasts, it acts as a donor in the reduction of oxidized chlorophyll. In this process, it loses the hydrogen atom of its phenolic OH-group and this radical is subsequently reduced in the photosystem II by the four core manganese clusters. The Recommended Dietary Allowance for phenylalanine and tyrosine is 33 mg per kilogram of body weight, for a 70 kg person this is 2310 mg. For example, the white of an egg has about 250 mg per egg, in plants and most microorganisms, tyr is produced via prephenate, an intermediate on the shikimate pathway. Mammals synthesize tyrosine from the amino acid phenylalanine, which is derived from food. The conversion of phe to tyr is catalyzed by the enzyme phenylalanine hydroxylase and this enzyme catalyzes the reaction causing the addition of a hydroxyl group to the end of the 6-carbon aromatic ring of phenylalanine, such that it becomes tyrosine. Some of the residues can be tagged with a phosphate group by protein kinases. In its phosphorylated form, tyrosine is called phosphotyrosine, tyrosine phosphorylation is considered to be one of the key steps in signal transduction and regulation of enzymatic activity. Phosphotyrosine can be detected through specific antibodies, tyrosine residues may also be modified by the addition of a sulfate group, a process known as tyrosine sulfation. Tyrosine sulfation is catalyzed by tyrosylprotein sulfotransferase, like the phosphotyrosine antibodies mentioned above, antibodies have recently been described that specifically detect sulfotyrosine
9.
Polymerization
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In polymer chemistry, polymerization is a process of reacting monomer molecules together in a chemical reaction to form polymer chains or three-dimensional networks. There are many forms of polymerization and different systems exist to categorize them, in chemical compounds, polymerization occurs via a variety of reaction mechanisms that vary in complexity due to functional groups present in reacting compounds and their inherent steric effects. Alkanes can also be polymerized, but only with the help of strong acids, further compounds either being referred to as oligomers in smaller molecules. Polymerization that is not sufficiently moderated and proceeds at a fast rate can be very hazardous and this phenomenon is known as hazardous polymerization and can cause fires and explosions. Step-growth polymers are defined as polymers formed by the reaction between functional groups of monomers, usually containing heteroatoms such as nitrogen or oxygen. Most step-growth polymers are classified as condensation polymers, but not all step-growth polymers release condensates, in this case. Step-growth polymers increase in weight at a very slow rate at lower conversions. To alleviate inconsistencies in these methods, adjusted definition for condensation and addition polymers have been developed. Chain-growth polymerization involves the linking together of molecules incorporating double or triple carbon-carbon bonds and these unsaturated monomers have extra internal bonds that are able to break and link up with other monomers to form a repeating chain, whose backbone typically contains only carbon atoms. Chain-growth polymerization is involved in the manufacture of such as polyethylene, polypropylene. A special case of chain-growth polymerization leads to living polymerization, in the radical polymerization of ethylene, its π bond is broken, and the two electrons rearrange to create a new propagating center like the one that attacked it. The form this propagating center takes depends on the type of addition mechanism. There are several mechanisms through which this can be initiated, the free radical mechanism is one of the first methods to be used. Free radicals are very reactive atoms or molecules that have unpaired electrons, taking the polymerization of ethylene as an example, the free radical mechanism can be divided into three stages, chain initiation, chain propagation, and chain termination. Free radical addition polymerization of ethylene must take place at temperatures and pressures. While most other free radical polymerizations do not require such extreme temperatures and pressures, one effect of this lack of control is a high degree of branching. Also, as termination occurs randomly, when two chains collide, it is impossible to control the length of individual chains, a newer method of polymerization similar to free radical, but allowing more control involves the Ziegler-Natta catalyst, especially with respect to polymer branching. Other forms of chain growth polymerization include cationic addition polymerization and anionic addition polymerization, cationic and anionic mechanisms are also more ideally suited for living polymerizations, although free radical living polymerizations have also been developed
10.
Melanin
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Melanin /ˈmɛlənɪn/ is a broad term for a group of natural pigments found in most organisms. Melanin is produced by the oxidation of the amino acid tyrosine, the pigment is produced in a specialized group of cells known as melanocytes. There are three types of melanin, eumelanin, pheomelanin, and neuromelanin. The most common is eumelanin, of which there are two types—brown eumelanin and black eumelanin, pheomelanin is a cysteine-containing red polymer of benzothiazine units largely responsible for red hair, among other pigmentation. Neuromelanin is found in the brain, though its function remains obscure, in the skin, melanogenesis occurs after exposure to UV radiation, causing the skin to visibly tan. Melanin is an effective absorber of light, the pigment is able to dissipate over 99. 9% of absorbed UV radiation, because of this property, melanin is thought to protect skin cells from UVB radiation damage, reducing the risk of cancer. e. Nonetheless, the relationship between skin pigmentation and photoprotection is still being clarified, in humans, melanin is the primary determinant of skin color. It is also found in hair, the pigmented tissue underlying the iris of the eye, in the brain, tissues with melanin include the medulla and pigment-bearing neurons within areas of the brainstem, such as the locus coeruleus and the substantia nigra. It also occurs in the zona reticularis of the adrenal gland, the melanin in the skin is produced by melanocytes, which are found in the basal layer of the epidermis. Although, in general, human beings possess a concentration of melanocytes in their skin. Some humans have very little or no melanin synthesis in their bodies, because melanin is an aggregate of smaller component molecules, there are many different types of melanin with differing proportions and bonding patterns of these component molecules. Both pheomelanin and eumelanin are found in skin and hair. Eumelanin polymers have long thought to comprise numerous cross-linked 5, 6-dihydroxyindole and 5. There are two types of eumelanin and black eumelanin—which chemically differ from each other in their pattern of polymeric bonds. A small amount of black eumelanin in the absence of other pigments causes grey hair, a small amount of brown eumelanin in the absence of other pigments causes blond color hair. As the body ages, it continues to produce black melanin but stops producing the brown version, pheomelanins impart a pink to red hue, depending upon the concentration. Pheomelanins are particularly concentrated in the lips, nipples, glans of the penis, when a small amount of brown eumelanin in hair, which would otherwise cause blond hair, is mixed with red pheomelanin, the result is red hair. Pheomelanin is also present in the skin, and redheads consequently often have a pinkish hue to their skin as well
11.
Neuromelanin
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Neuromelanin is a dark pigment found in the brain which is structurally related to melanin. It is a polymer of 5, 6-dihydroxyindole monomers, neuromelanin is expressed in large quantities in catecholaminergic cells of the substantia nigra pars compacta and locus coeruleus, giving dark color to the structures. Neuromelanin is found in higher concentrations among humans than in other primates, neuromelanin-containing neurons in the substantia nigra undergo neurodegeneration during Parkinsons disease. Neuromelanin concentration increases with age, suggesting a role in neuroprotection or senescence, neuromelanin is directly biosynthesized from L-DOPA, precursor to dopamine, by tyrosine hydroxylase and aromatic acid decarboxylase. Alternatively, synaptic vesicles and endosomes accumulate cytosolic dopamine (via vesicular monoamine transporter 2, excess dopamine and DOPA molecules are oxidized by iron catalysis into quinones and semiquinones which are then phagocytosed and are stored as neuromelanin. Motor symptoms of Parkinsons disease are caused by death in the substantia nigra. This oxidation may be relieved by neuromelanin, patients with Parkinsons disease had 50% the amount of neuromelanin in the substantia nigra as compared to similar patients of their same age, but without Parkinsons. Neuromelanin has been shown to bind neurotoxic and toxic metals that could promote neurodegeneration, neuromelanin biosynthesis is driven by excess cytosolic catecholamines not accumulated by synaptic vesicles. Neuromelanin gives specific brain sections, such as the substantia nigra or the locus coeruleus and it is a type of melanin and similar to other forms of peripheral melanin. It is insoluble in organic compounds, and can be labeled by silver stains and it is called neuromelanin because of its function and the color change that appears in tissues containing it. Neuromelanin is found to accumulate during ageing and is found during the first 2–3 years of life and it is believed to protect neurons in the substantia nigra from iron-induced oxidative stress. It is considered a true melanin due to its stable free radical structure and it is now believed to play a vital role in preventing cell death in certain parts of the brain. It has been linked to Parkinsons disease and because of possible connection
12.
Cysteine
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Cysteine is a semi-essential proteinogenic amino acid with the formula HO2CCHCH2SH. It is encoded by the codons UGU and UGC, the thiol side chain in cysteine often participates in enzymatic reactions, as a nucleophile. The thiol is susceptible to oxidization to give the disulfide derivative cystine, when used as a food additive, it has the E number E920. It can be seen as serine, but with one of the oxygen replaced with sulfur. Cysteine can usually be synthesized by the body under normal physiological conditions if a sufficient quantity of methionine is available. Cysteine is catabolized in the tract and blood plasma. In contrast, cystine travels safely through the GI tract and blood plasma and is reduced to the two cysteine molecules upon cell entry. Like other amino acids, cysteine has an amphoteric character, the majority of L-cysteine is obtained industrially by hydrolysis of animal materials, such as poultry feathers or hog hair. Despite widespread belief otherwise, there is evidence that human hair is used as a source material. Synthetically produced L-cysteine, compliant with Jewish kosher and Muslim halal laws, is also available, the synthetic route involves fermentation using a mutant of E. coli. Degussa introduced a route from substituted thiazolines, following this technology, L-cysteine is produced by the hydrolysis of racemic 2-amino-Δ2-thiazoline-4-carboxylic acid using Pseudomonas thiazolinophilum. In animals, biosynthesis begins with the amino acid serine, the sulfur is derived from methionine, which is converted to homocysteine through the intermediate S-adenosylmethionine. Cystathionine beta-synthase then combines homocysteine and serine to form the asymmetrical thioether cystathionine, the enzyme cystathionine gamma-lyase converts the cystathionine into cysteine and alpha-ketobutyrate. In plants and bacteria, cysteine biosynthesis also starts from serine, the enzyme O-acetylserine -lyase, using sulfide sources, converts this ester into cysteine, releasing acetate. The cysteine thiol group is nucleophilic and easily oxidized, the reactivity is enhanced when the thiol is ionized, and cysteine residues in proteins have pKa values close to neutrality, so are often in their reactive thiolate form in the cell. Because of its reactivity, the thiol group of cysteine has numerous biological functions. Due to the ability of thiols to undergo reactions, cysteine has antioxidant properties. Cysteines antioxidant properties are typically expressed in the tripeptide glutathione, which occurs in humans as well as other organisms, the systemic availability of oral glutathione is negligible, so it must be biosynthesized from its constituent amino acids, cysteine, glycine, and glutamic acid
13.
Benzothiazine
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Benzothiazine is a heterocyclic compound consisting of a benzene ring attached to the 6-membered heterocycle thiazine. The name is applied to both the 2H- and 4H-isomers of the molecule,2, 1-Benzothiazine, a type of benzothiazines was first reported in the 1960s. Subsequently, their preparation and intensive biological and physiological studies have been reported, in recent years,2, 1-benzothiazines have been of enormous interest to synthetic chemists. Phenothiazine has a benzene ring Benzothiazole is another heterocycle containing nitrogen. Recent Progress in the Chemistry of 2, 1-Benzothiazines, Progress in Hetereocyclic Chemistry, Chapter 1, G. W. Gribble and J. A. Joule, eds, Pergamon Press, Vol 19, pp 1-433. The Intramolecular, Stereoselective Addition of Sulfoximine Carbanions to α, β-Unsaturated Esters, harmata, M. Hong, X. Journal of the American Chemical Society,2003,125, 5754-5756. Harmata, M. Hong, X. Organic Letters,2005,7, 3581-3583
14.
Red hair
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Red hair occurs naturally in 1–2% of the human population. It occurs more frequently in people of northern or western European ancestry, Red hair appears most commonly in people with two copies of a recessive allele on chromosome 16 which produces an altered version of the MC1R protein. Red hair varies in hues from a deep burgundy or bright copper through to burnt orange or red-orange and it is characterized by high levels of the reddish pigment pheomelanin and relatively low levels of the dark pigment eumelanin. It is associated with skin color, lighter eye colors, freckles. Cultural reactions have varied from ridicule to admiration, many stereotypes exist regarding redheads. The term redhead has been in use since at least 1510, several accounts by Greek writers mention redheaded people. A fragment by the poet Xenophanes describes the Thracians as blue-eyed and red-haired, in Asia, red hair has been found among the ancient Tocharians, who occupied the Tarim Basin in what is now the northwesternmost province of China. Caucasian Tarim mummies have been found with red hair dating to the 2nd millennium BC, reddish-brown hair is also found amongst some Polynesians, and is especially common in some tribes and family groups. In Polynesian culture reddish hair has traditionally seen as a sign of descent from high-ranking ancestors. Red hair is most commonly found at the northern and western fringes of Europe, redheads today are commonly associated with the Celtic Nations and to a far lesser extent the Germanic peoples. Over the years there have been a number of studies measuring the percentage of redheads within the UK, exact figures, and methods, vary, but they all are in agreement that the highest percentages in the world are within these isles. England has a red hair prevalence of around 4%, with 28. 5% of population having the allele, in Ireland, the percentage of population with red hair is estimated to be at around 10%. According to Britains DNA,34. 7% of the Irish population carry the allele for red hair, Scotland also has a very high percentage with around 6% of the population having red hair. Previously it was estimated that red hair occurrence in Scotland was around 13%, the largest ever study of hair colour in Scotland, which analysed over 500,000 people in 1907, found the percentage of Scots with red hair to be 5. 3%. 38% of Welsh people carry the red-haired allele, a 1956 study of hair colour among British army recruits found higher levels of red hair in Wales and the English Border counties. Carleton Coons 1939 book The Races of Europe stated that rufosity often occurred in Montenegrins, in Italy, red hair is found at a frequency of 0. 57% of the total population, without variation in frequency across the different regions of the country. In Sardinia, red hair is found at a frequency of 0. 24% of the population, the Berber populations of Morocco and northern Algeria have occasional redheads. Red hair frequency is especially significant among the Riffians from Morocco and Kabyles from Algeria, the Queen of Morocco, Lalla Salma wife of king Mohammed VI, has red hair
15.
Brain
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The brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. The brain is located in the head, usually close to the organs for senses such as vision. The brain is the most complex organ in a vertebrates body, in a human, the cerebral cortex contains approximately 15–33 billion neurons, each connected by synapses to several thousand other neurons. Physiologically, the function of the brain is to exert centralized control over the other organs of the body, the brain acts on the rest of the body both by generating patterns of muscle activity and by driving the secretion of chemicals called hormones. This centralized control allows rapid and coordinated responses to changes in the environment, the operations of individual brain cells are now understood in considerable detail but the way they cooperate in ensembles of millions is yet to be solved. This article compares the properties of brains across the range of animal species. It deals with the human brain insofar as it shares the properties of other brains, the ways in which the human brain differs from other brains are covered in the human brain article. Several topics that might be covered here are instead covered there because more can be said about them in a human context. The most important is brain disease and the effects of brain damage, the shape and size of the brain varies greatly between species, and identifying common features is often difficult. Nevertheless, there are a number of principles of architecture that apply across a wide range of species. Some aspects of structure are common to almost the entire range of animal species, others distinguish advanced brains from more primitive ones. The simplest way to gain information about brain anatomy is by visual inspection, Brain tissue in its natural state is too soft to work with, but it can be hardened by immersion in alcohol or other fixatives, and then sliced apart for examination of the interior. Visually, the interior of the consists of areas of so-called grey matter, with a dark color, separated by areas of white matter. Further information can be gained by staining slices of tissue with a variety of chemicals that bring out areas where specific types of molecules are present in high concentrations. It is also possible to examine the microstructure of brain tissue using a microscope, the brains of all species are composed primarily of two broad classes of cells, neurons and glial cells. Glial cells come in types, and perform a number of critical functions, including structural support, metabolic support, insulation. Neurons, however, are considered the most important cells in the brain. The property that makes neurons unique is their ability to send signals to target cells over long distances
16.
Ultraviolet
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Ultraviolet is an electromagnetic radiation with a wavelength from 10 nm to 400 nm, shorter than that of visible light but longer than X-rays. UV radiation constitutes about 10% of the light output of the Sun. It is also produced by electric arcs and specialized lights, such as lamps, tanning lamps. Consequently, the effects of UV are greater than simple heating effects. Suntan, freckling and sunburn are familiar effects of over-exposure, along with risk of skin cancer. Living things on dry land would be damaged by ultraviolet radiation from the Sun if most of it were not filtered out by the Earths atmosphere. More-energetic, shorter-wavelength extreme UV below 121 nm ionizes air so strongly that it is absorbed before it reaches the ground, Ultraviolet is also responsible for the formation of bone-strengthening vitamin D in most land vertebrates, including humans. The UV spectrum thus has both beneficial and harmful to human health. Ultraviolet rays are invisible to most humans, the lens in a human eye ordinarily filters out UVB frequencies or higher, and humans lack color receptor adaptations for ultraviolet rays. Under some conditions, children and young adults can see ultraviolet down to wavelengths of about 310 nm, near-UV radiation is visible to some insects, mammals, and birds. Small birds have a fourth color receptor for ultraviolet rays, this gives birds true UV vision, reindeer use near-UV radiation to see polar bears, who are poorly visible in regular light because they blend in with the snow. UV also allows mammals to see urine trails, which is helpful for animals to find food in the wild. The males and females of some species look identical to the human eye. Ultraviolet means beyond violet, violet being the color of the highest frequencies of visible light, Ultraviolet has a higher frequency than violet light. He called them oxidizing rays to emphasize chemical reactivity and to them from heat rays. The terms chemical and heat rays were eventually dropped in favour of ultraviolet and infrared radiation, in 1878 the effect of short-wavelength light on sterilizing bacteria was discovered. By 1903 it was known the most effective wavelengths were around 250 nm, in 1960, the effect of ultraviolet radiation on DNA was established. The discovery of the ultraviolet radiation below 200 nm, named vacuum ultraviolet because it is absorbed by air, was made in 1893 by the German physicist Victor Schumann
17.
Indirect DNA damage
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Indirect DNA damage occurs when a UV-photon is absorbed in the human skin by a chromophore that does not have the ability to convert the energy into harmless heat very quickly. Molecules that do not have this ability have an excited state. This long lifetime leads to a probability for reactions with other molecules - so-called bimolecular reactions. Melanin and DNA have extremely short excited state lifetimes in the range of a few femtoseconds. The excited state lifetime of these substances is 1,000 to 1,000,000 times longer than the lifetime of melanin, the molecule that originally absorbs the UV-photon is called a chromophore. Bimolecular reactions can occur either between the chromophore and DNA or between the excited chromophore and another species, to produce free radicals and Reactive Oxygen Species. These reactive chemical species can reach DNA by diffusion and the bimolecular reaction damages the DNA and it is important to note that indirect DNA damage does not result in any warning signal or pain in the human body. Sunscreen photoprotection direct DNA damage Free radical damage to DNA
18.
Human skin color
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Human skin color ranges in variety from the darkest brown to the lightest hues. An individuals skin pigmentation is the result of genetics, being the product of both of the biological parents genetic makeup. The actual skin color of different humans is affected by many substances, melanin is produced within the skin in cells called melanocytes and it is the main determinant of the skin color of darker-skinned humans. The skin color of people with skin is determined mainly by the bluish-white connective tissue under the dermis. The red color underlying the skin becomes more visible, especially in the face, Color is not entirely uniform across an individuals skin, for example, the skin of the palm and the sole is lighter than most other skin, and this is especially noticeable in darker-skinned people. There is a correlation between the geographic distribution of UV radiation and the distribution of indigenous skin pigmentation around the world. Areas that receive higher amounts of UVR, generally located closer to the equator, areas that are far from the tropics and closer to the poles have lower intensity of UVR, which is reflected in lighter-skinned populations. Natural skin color can darken as a result of tanning due to exposure to sunlight. In addition, it has observed that adult human females on average are significantly lighter in skin pigmentation than males. Females need more calcium during pregnancy and lactation, the body synthesizes vitamin D from sunlight, which helps it absorb calcium. Females evolved to have lighter skin so their bodies absorb more calcium, the social significance of differences in skin color has varied across cultures and over time, as demonstrated with regard to social status and discrimination. Melanin is produced by cells called melanocytes in a process called melanogenesis, melanin is made within small membrane–bound packages called melanosomes. As they become full of melanin, they move into the arms of melanocytes. Under normal conditions, melanosomes cover the part of the keratinocytes. One melanocyte supplies melanin to thirty-six keratinocytes according to signals from the keratinocytes and they also regulate melanin production and replication of melanocytes. People have different skin colors mainly because their melanocytes produce different amount, the genetic mechanism behind human skin color is mainly regulated by the enzyme tyrosinase, which creates the color of the skin, eyes, and hair shades. Differences in skin color are also attributed to differences in size, melanocytes produce two types of melanin. The most common form of melanin is eumelanin, a brown-black polymer of dihydroxyindole carboxylic acids
19.
Papua New Guinea
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Its capital, located along its southeastern coast, is Port Moresby. The western half of New Guinea forms the Indonesian provinces of Papua, Papua New Guinea is one of the most culturally diverse countries in the world. There are 852 known languages in the country, of which 12 have no known living speakers, most of the population of more than 7 million people live in customary communities, which are as diverse as the languages. It is also one of the most rural, as only 18 percent of its live in urban centres. The country is one of the worlds least explored, culturally and geographically and it is known to have numerous groups of uncontacted peoples, and researchers believe there are many undiscovered species of plants and animals in the interior. Papua New Guinea is classified as an economy by the International Monetary Fund. Strong growth in Papua New Guineas mining and resource sector led to the becoming the sixth fastest-growing economy in the world in 2011. Growth was expected to slow once major resource projects came on line in 2015, mining remains a major economic factor, however. Local and national governments are discussing the potential of resuming mining operations in Panguna mine in Bougainville Province, nearly 40 percent of the population lives a self-sustainable natural lifestyle with no access to global capital. Most of the still live in strong traditional social groups based on farming. Their social lives combine traditional religion with modern practices, including primary education, at the national level, after being ruled by three external powers since 1884, Papua New Guinea established its sovereignty in 1975. This followed nearly 60 years of Australian administration, which started during the Great War and it became an independent Commonwealth realm with Queen Elizabeth II as its head of state and became a member of the Commonwealth of Nations in its own right. Archaeological evidence indicates that humans first arrived in Papua New Guinea around 42,000 to 45,000 years ago and they were descendants of migrants out of Africa, in one of the early waves of human migration. Agriculture was independently developed in the New Guinea highlands around 7000 BC, a major migration of Austronesian-speaking peoples to coastal regions of New Guinea took place around 500 BC. This has been correlated with the introduction of pottery, pigs, in the 18th century, traders brought the sweet potato to New Guinea, where it was adopted and became part of the staples. Portuguese traders had obtained it from South America and introduced it to the Moluccas, the far higher crop yields from sweet potato gardens radically transformed traditional agriculture and societies. Sweet potato largely supplanted the previous staple, taro, and resulted in a significant increase in population in the highlands. In 1901, on Goaribari Island in the Gulf of Papua, missionary Harry Dauncey found 10,000 skulls in the islands Long Houses, traders from Southeast Asia had visited New Guinea beginning 5,000 years ago to collect bird of paradise plumes
20.
Adrenal medulla
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The adrenal medulla is part of the adrenal gland. It is located at the center of the gland, being surrounded by the adrenal cortex, the adrenal medulla consists of irregularly shaped cells grouped around blood vessels. These cells are connected with the sympathetic division of the autonomic nervous system. In fact, these adrenal medullary cells are modified postganglionic neurons, the adrenal medulla therefore affects available energy, heart rate, and metabolism. Recent research indicates that the adrenal medulla is under the control of the sensory, rather than releasing a neurotransmitter, the cells of the adrenal medulla secrete hormones. Because the ANS, specifically the sympathetic division, exerts direct control over the cells the hormone release can occur rather quickly. In response to such as exercise or imminent danger, medullary cells release the catecholamines adrenaline and noradrenaline into the blood. Adrenaline composes about 85% of the catecholamines, and noradrenaline the other 15%. Release of catecholamines is stimulated by nerve impulses, and receptors for catecholamines are widely distributed throughout the body, medullary cells are derived from the embryonic neural crest and, as such, are simply modified neurons. In particular, they are modified postganglionic cells of the nervous system that have lost their axons and dendrites. The cells form clusters around large blood vessels, as a cluster of neuron cell bodies, the adrenal medulla is considered a ganglion of the sympathetic nervous system.292 - Adrenal Gland
21.
Locus coeruleus
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The locus coeruleus is a nucleus in the pons involved with physiological responses to stress and panic. The locus coeruleus is the site for brain synthesis of norepinephrine. The locus coeruleus and the areas of the affected by the norepinephrine it produces are described collectively as the locus coeruleus-noradrenergic system or LC-NA system. Norepinephrine may also be released directly into the blood from the adrenal medulla, the locus coeruleus is located in the posterior area of the rostral pons in the lateral floor of the fourth ventricle. It is composed of mostly medium-size neurons, melanin granules inside the neurons of the LC contribute to its blue color. Thus, it is known as the nucleus pigmentosus pontis. The neuromelanin is formed by the polymerization of noradrenaline and is analogous to the black dopamine-based neuromelanin in the substantia nigra. In adult humans the locus coeruleus has 22,000 to 51,000 total pigmented neurons that range in size between 31,000 and 60,000 μm3, the projections of this nucleus reach far and wide. For example, they innervate the spinal cord, the stem, cerebellum, hypothalamus, the thalamic relay nuclei, the amygdala, the basal telencephalon. The norepinephrine from the LC has an effect on most of the brain, mediating arousal. As an important homeostatic control center of the body, the locus coeruleus receives afferents from the hypothalamus, the cingulate gyrus and the amygdala also innervate the LC, allowing emotional pain and stressors to trigger noradrenergic responses. The cerebellum and afferents from the raphe nuclei also project to the LC, in particular the nucleus raphes pontis, the projections from the locus coeruleus consist of neurons that utilize norepinephrine as their primary neurotransmitter. The LC-NA system modulates cortical, subcortical, cerebellar, brainstem, the locus coeruleus may figure in clinical depression, panic disorder, Parkinsons disease, Alzheimers disease and anxiety. Research continues to reveal that norepinephrine is a regulator of numerous activities from stress response. Many neuropsychiatric disorders precipitate from alterations to NE modulated neurocircuitry, disorders of affect, anxiety disorders, PTSD, ADHD, alterations in the locus coeruleus accompany dysregulation of NE function and likely play a key role in the pathophysiology of these neuropsychiatric disorders. The locus coeruleus is responsible for mediating many of the sympathetic effects during stress, the LCs role in cognitive function in relation to stress is complex and multi-modal. Norepinephrine released from the LC can act on α2 receptors to increase working memory, the LC neurons are probably the origin of the first or second “leg” of the PTSD circuit. Opioids inhibit the firing of neurons in the locus coeruleus, when opioid consumption is stopped, the increased activity of the locus coeruleus contributes to the symptoms of opiate withdrawal
22.
Zona reticularis
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The zona reticularis is the innermost layer of the adrenal cortex, lying deep to the zona fasciculata and superficial to the adrenal medulla. The cells are arranged cords that project in different directions giving a net-like appearance, cells in the zona reticularis produce precursor androgens including dehydroepiandrosterone and androstenedione from cholesterol. DHEA is further converted to DHEA-sulfate via a sulfotransferase, SULT2A1 and these precursors are not further converted in the adrenal cortex if the cells lack 17Beta Hydroxysteroid dehydrogenase. Instead, they are released into the stream and taken up in the testis and ovaries to produce testosterone. ACTH partially regulates adrenal androgen secretion, also CRH, in humans the reticularis layer does contain 17 alpha-hydroxylase, this hydroxylates pregnenolone, which is then converted to cortisol by a mixed function oxidase. In rodents, the lack of 17alpha-hydroxylase results in the synthesis of corticosterone instead of cortisol as in the human, Histology image, 14502loa – Histology Learning System at Boston University Anatomy Atlases - Microscopic Anatomy, plate 15.292 - Adrenal Gland
23.
Stratum basale
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The stratum basale is the deepest layer of the five layers of the epidermis, the outer covering of skin in mammals. The stratum basale is a layer of cells. It is often described as one thick, though it may in fact be two to three cells thick in glabrous skin, and hyperproliferative epidermis. The stratum basale is primarily made up of basal keratinocyte stem cells and they divide to form the keratinocytes of the stratum spinosum, which migrate superficially. Other types of cells found within the stratum basale are melanocytes, Langerhans cells, list of keratins expressed in the human integumentary system
24.
Epidermis
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The epidermis is the outer of the two layers that make up the skin, the inner layer being the dermis. It provides a barrier to infection from pathogens and regulates the amount of water released from the body into the atmosphere through transepidermal water loss. The outermost part of the epidermis is composed of stratified layers of flattened cells, the epidermis has no blood supply and is nourished almost exclusively by diffused oxygen from the surrounding air. It is 95% keratinocytes but also contains melanocytes, Langerhans cells, Merkel cells, rete ridges are epidermal thickenings that extend downward between dermal papillae. Blood capillaries are found beneath the epidermis, and are linked to an arteriole, the epidermis is composed of 4 or 5 layers depending on the region of skin being considered. Those layers in descending order are, cornified layer Composed of 10 to 30 layers of polyhedral, anucleated corneocytes, with the palms, most of the barrier functions of the epidermis localize to this layer. Clear/translucent layer The skin found in the palms and soles is known as thick skin because it has 5 epidermal layers instead of 4, granular layer Keratinocytes lose their nuclei and their cytoplasm appears granular. Lipids, contained into those keratinocytes within lamellar bodies, are released into the space through exocytosis to form a lipid barrier. Those polar lipids are then converted into non-polar lipids and arranged parallel to the cell surface, for example glycosphingolipids become ceramides and phospholipids become free fatty acids. Langerhans cells, immunologically active cells, are located in the middle of this layer, Composed mainly of proliferating and non-proliferating keratinocytes, attached to the basement membrane by hemidesmosomes. Melanocytes are present, connected to numerous keratinocytes in this and other strata through dendrites, Merkel cells are also found in the stratum basale with large numbers in touch-sensitive sites such as the fingertips and lips. They are closely associated with cutaneous nerves and seem to be involved in light touch sensation, the term Malpighian layer is usually defined as both the stratum basale and stratum spinosum. The epidermis is separated from the dermis, its underlying tissue, the stratified squamous epithelium is maintained by cell division within the stratum basale. Differentiated keratinocytes secrete keratin proteins which contribute to the formation of a matrix and is an integral part of the skin barrier function. The entire epidermis is replaced by new growth over a period of about 48 days. Calcium concentration in the stratum corneum is very low in part because those relatively dry cells are not able to dissolve the ions and this calcium gradient parallels keratinocyte differentiation and as such is considered a key regulator in the formation of the epidermal layers. Elevation of extracellular calcium concentrations induces an increase in intracellular free calcium concentrations, moreover, it has been suggested that an extracellular calcium-sensing receptor also contributes to the rise in intracellular calcium concentration. Epidermal organogenesis, the formation of the epidermis, begins in the covering the embryo after neurulation
25.
Indole
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Indole is an aromatic heterocyclic organic compound with formula C8H7N. It has a structure, consisting of a six-membered benzene ring fused to a five-membered nitrogen-containing pyrrole ring. Indole is widely distributed in the environment and can be produced by a variety of bacteria. As an intercellular signal molecule, indole regulates various aspects of physiology, including spore formation, plasmid stability, resistance to drugs, biofilm formation. The amino acid tryptophan is a derivative and the precursor of the neurotransmitter serotonin. Indole is a solid at room temperature, Indole can be produced by bacteria as a degradation product of the amino acid tryptophan. It occurs naturally in feces and has an intense fecal odor. At very low concentrations, however, it has a flowery smell and it also occurs in coal tar. The corresponding substituent is called indolyl, Indole undergoes electrophilic substitution, mainly at position 3. Substituted indoles are structural elements of the tryptophan-derived tryptamine alkaloids like the neurotransmitter serotonin, other indolic compounds include the plant hormone auxin, tryptophol, the anti-inflammatory drug indomethacin, the betablocker pindolol, and the naturally occurring hallucinogen dimethyltryptamine. The name indole is a portmanteau of the indigo and oleum. Indole chemistry began to develop with the study of the dye indigo, indigo can be converted to isatin and then to oxindole. Then, in 1866, Adolf von Baeyer reduced oxindole to indole using zinc dust, in 1869, he proposed a formula for indole. Certain indole derivatives were important dyestuffs until the end of the 19th century, in the 1930s, interest in indole intensified when it became known that the indole substituent is present in many important alkaloids, and it remains an active area of research today. It condenses with serine by Michael addition of indole to PLP-aminoacrylate, as an intercellular signal molecule, indole regulates various aspects of bacterial physiology, including spore formation, plasmid stability, resistance to drugs, biofilm formation, and virulence. The amino acid tryptophan is a derivative and the precursor of the neurotransmitter serotonin. Indole is a constituent of coal tar, and the 220–260 °C distillation fraction is the main industrial source of the material. Indole and its derivatives can also be synthesized by a variety of methods, the main industrial routes start from aniline via vapor-phase reaction with ethylene glycol in the presence of catalysts, In general, reactions are conducted between 200 and 500 °C
26.
Carboxylic acid
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A carboxylic acid /ˌkɑːrbɒkˈsɪlɪk/ is an organic compound that contains a carboxyl group. The general formula of an acid is R–COOH, with R referring to the rest of the molecule. Carboxylic acids occur widely and include the amino acids and acetic acid, salts and esters of carboxylic acids are called carboxylates. When a carboxyl group is deprotonated, its conjugate base forms a carboxylate anion, carboxylate ions are resonance-stabilized, and this increased stability makes carboxylic acids more acidic than alcohols. Carboxylic acids can be seen as reduced or alkylated forms of the Lewis acid carbon dioxide, carboxylic acids are commonly identified using their trivial names, and usually have the suffix -ic acid. IUPAC-recommended names also exist, in system, carboxylic acids have an -oic acid suffix. For example, butyric acid is butanoic acid by IUPAC guidelines, the -oic acid nomenclature detail is based on the name of the previously-known chemical benzoic acid. Alternately, it can be named as a carboxy or carboxylic acid substituent on another parent structure, for example, 2-carboxyfuran. The carboxylate anion of an acid is usually named with the suffix -ate, in keeping with the general pattern of -ic acid and -ate for a conjugate acid and its conjugate base. For example, the base of acetic acid is acetate. The radical •COOH has only a fleeting existence. The acid dissociation constant of •COOH has been measured using electron paramagnetic resonance spectroscopy, the carboxyl group tends to dimerise to form oxalic acid. Because they are both hydrogen-bond acceptors and hydrogen-bond donors, they participate in hydrogen bonding. Together the hydroxyl and carbonyl group forms the functional group carboxyl, carboxylic acids usually exist as dimeric pairs in nonpolar media due to their tendency to self-associate. Smaller carboxylic acids are soluble in water, whereas higher carboxylic acids are less due to the increasing hydrophobic nature of the alkyl chain. These longer chain acids tend to be soluble in less-polar solvents such as ethers. Carboxylic acids tend to have higher boiling points than water, not only because of their surface area. Carboxylic acids tend to evaporate or boil as these dimers, for boiling to occur, either the dimer bonds must be broken or the entire dimer arrangement must be vaporised, both of which increase the enthalpy of vaporization requirements significantly
27.
Blond
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Blond, blonde, or fair hair, is a hair color characterized by low levels of the dark pigment eumelanin. The resultant visible hue depends on various factors, but always has some sort of yellowish color, the color can be from the very pale blond to reddish strawberry blond or golden-brownish blond colors. On the Fischer–Saller scale, blond color ranges from A to O, the word blond is first documented in English in 1481 and derives from Old French blund, blont meaning a colour midway between golden and light chestnut. It gradually eclipsed the native term fair, of meaning, from Old English fæġer. This earlier use of fair survives in the proper name Fairfax, the French word blond has two possible origins. Also, Old English beblonden meant dyed as ancient Germanic warriors were noted for dyeing their hair, however, linguists who favor a Latin origin for the word say that Medieval Latin blundus was a vulgar pronunciation of Latin flavus, also meaning yellow. Most authorities, especially French, attest the Frankish origin, the word was reintroduced into English in the 17th century from French, and was for some time considered French, in French, blonde is a feminine adjective, it describes a woman with blonde hair. Blond, with its continued gender-varied usage, is one of few adjectives in written English to retain separate masculine and feminine grammatical genders, each of the two forms, however, is pronounced identically. The Oxford English Dictionary records that the phrase big blond beast was used in the 20th century to refer specifically to men of the Nordic type. The OED also records that blond as an adjective is used with reference to women, in which case it is likely to be spelt blonde. By the early 1990s, blonde moment or being a dumb blonde had come into common parlance to mean an instance of a person, another hair color word of French origin, brunet, also functions in the same way in orthodox English. Brunette can be used, however, like blonde, to describe a mixed-gender populace, the OED quotes Grant Allen, The nation which resulted. Blond and blonde are also used to refer to objects that have a color reminiscent of fair hair. Various subcategories of blond hair have been defined to describe the different shades and sources of the color more accurately. Common examples include the following, ash-blond, ashen or grayish blond, bleached blond, bottle blond, or peroxide blond terms used to refer to artificially colored blond hair. Blond/flaxen, when distinguished from other varieties, blond by itself refers to a light but not whitish blond, with no traces of red, gold, or brown, dirty blond or dishwater blond, dark blond with flecks of golden blond and brown. Golden blond, a darker to rich, golden-yellow blond, honey blond or caramel blond, dark iridescent blond. Platinum blond or towheaded, whitish-blond, almost all platinum blonds are children, platinum blond is often used to describe bleached hair, while towheaded generally refers to natural hair color
28.
Benzothiazole
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Benzothiazole is an aromatic heterocyclic compound with the chemical formula C 7H 5NS. It is colorless, slightly viscous liquid, although the parent compound, benzothiazole is not widely used, many of its derivatives are found in commercial products or in nature. A derivative of benzothiazole is the component of luciferin, found in fireflies. Benzothiazoles consist of a 5-membered 1, 3-thiazole ring fused to a benzene ring, the nine atoms of the bicycle and the attached substituents are coplanar. It is a thermally stable electron-withdrawing moiety with numerous applications in such as thioflavin. Some drugs contain this group, examples being riluzole and pramipexole, the heterocycle is found in nature. Accelerators for the vulcanization of rubber are based on 2-mercaptobenzothiazole and this ring is a potential component in nonlinear optics. The compound is used also used as an insecticide and food flavoring agent, benzothiazoles are related to thiazoles, which lack the fused benzene ring. Benzoxazoles, which substitute an oxygen for the sulfur atom
29.
Metabolic pathway
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In biochemistry, a metabolic pathway is a linked series of chemical reactions occurring within a cell. The reactants, products, and intermediates of a reaction are known as metabolites. In a metabolic pathway, the product of one acts as the substrate for the next. These enzymes often require dietary minerals, vitamins, and other cofactors to function, different metabolic pathways function based on the position within a eukaryotic cell and the significance of the pathway in the given compartment of the cell. For instance, the citric cycle, electron transport chain. In contrast, glycolysis, pentose phosphate pathway, and fatty acid biosynthesis all occur in the cytosol of a cell, the two pathways complement each other in that the energy released from one is used up by the other. The degradative process of a catabolic pathway provides the required to conduct a biosynthesis of an anabolic pathway. In addition to the two distinct metabolic pathways is the pathway, which can be either catabolic or anabolic based on the need for or the availability of energy. The end product of a pathway may be used immediately, initiate another metabolic pathway or be stored for later use, metabolic pathways are often considered to flow in one direction. Although all chemical reactions are reversible, conditions in the cell are often such that it is thermodynamically more favorable for flux to flow in one direction of a reaction. For example, one pathway may be responsible for the synthesis of an amino acid. One example of an exception to rule is the metabolism of glucose. Glycolysis results in the breakdown of glucose, but several reactions in the pathway are reversible. Glycolysis was the first metabolic pathway discovered, As glucose enters a cell, metabolic pathways are often regulated by feedback inhibition. Some metabolic pathways flow in a cycle wherein each component of the cycle is a substrate for the subsequent reaction in the cycle, the net reaction is, therefore, thermodynamically favorable, for it results in a lower free energy for the final products. A catabolic pathway is a system that produces chemical energy in the form of ATP, GTP, NADH, NADPH, FADH2, etc. from energy containing sources such as carbohydrates, fats. The end products are carbon dioxide, water, and ammonia. Coupled with an reaction of anabolism, the cell can synthesize new macromolecules using the original precursors of the anabolic pathway
30.
Transition metal
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Many scientists describe a transition metal as any element in the d-block of the periodic table, which includes groups 3 to 12 on the periodic table. In actual practice, the lanthanide and actinide series are also considered transition metals and are called inner transition metals. Cotton and Wilkinson expand the brief IUPAC definition by specifying which elements are included, as well as the elements of groups 4 to 11, they add scandium and yttrium in group 3 which have a partially filled d subshell in the metallic state. These last two elements are included even though they do not seem to possess the properties which are so characteristic of the transition metals in general. Lanthanum and actinium in Group 3 are however classified as lanthanides and actinides respectively and these elements are now known as the d-block. In the d-block the atoms of the elements have between 1 and 10 d electrons, Sc and Y in Group 3 are also generally recognized as transition metals. However the elements La–Lu and Ac–Lr and Group 12 attract different definitions from different authors, many chemistry textbooks and printed periodic tables classify La and Ac as Group 3 elements and transition metals, since their atomic ground-state configurations are s2d1 like Sc and Y. The elements Ce-Lu are considered as the series and Th-Lr as the actinide series. The two series together are classified as elements, or as inner transition elements. Some inorganic chemistry textbooks include La with the lanthanides and Ac with the actinides, a third classification defines the f-block elements as La-Yb and Ac-No, while placing Lu and Lr in Group 3. This is based on the Aufbau principle for filling electron subshells, in which 4f is filled before 5d, zinc, cadmium, and mercury are generally excluded from the transition metals as they have the electronic configuration d10s2, with no incomplete d shell. In the oxidation state +2 the ions have the electronic configuration d10, however, these elements can exist in other oxidation states, including the +1 oxidation state, as in the diatomic ion Hg2+2. The group 12 elements Zn, Cd and Hg may therefore, under certain rules, however, it is often convenient to include these elements in a discussion of the transition elements. Another example occurs in the Irving-Williams series of stability constants of complexes, although meitnerium, darmstadtium, and roentgenium are within the d-block and are expected to behave as transition metals, this has not yet been experimentally confirmed. The general electronic configuration of the elements is d1, 10n s1,2. The period 6 and 7 transition metals also add f1,14 electrons and this rule is however only approximate – it only holds for some of the transition elements, and only then in their neutral ground state. The d-sub-shell is the next-to-last sub-shell and is denoted as d -sub-shell, the number of s electrons in the outermost s sub-shell is generally one or two except palladium, with no electron in that s-sub shell in its ground state. The s-sub-shell in the shell is represented as the ns sub-shell
31.
Apoptosis
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Apoptosis is a process of programmed cell death that occurs in multicellular organisms. Biochemical events lead to characteristic cell changes and death and these changes include blebbing, cell shrinkage, nuclear fragmentation, chromatin condensation, chromosomal DNA fragmentation, and global mRNA decay. Between 50 and 70 billion cells die each day due to apoptosis in the human adult. For an average child between the ages of 8 and 14, approximately 20 billion to 30 billion cells die a day, for example, the separation of fingers and toes in a developing human embryo occurs because cells between the digits undergo apoptosis. Because apoptosis cannot stop once it has begun, it is a regulated process. Apoptosis can be initiated through one of two pathways, in the intrinsic pathway the cell kills itself because it senses cell stress, while in the extrinsic pathway the cell kills itself because of signals from other cells. Both pathways induce cell death by activating caspases, which are proteases, the two pathways both activate initiator caspases, which then activate executioner caspases, which then kill the cell by degrading proteins indiscriminately. Research on apoptosis has increased substantially since the early 1990s, in addition to its importance as a biological phenomenon, defective apoptotic processes have been implicated in a wide variety of diseases. Excessive apoptosis causes atrophy, whereas an insufficient amount results in uncontrolled cell proliferation, some factors like Fas receptors and caspases promote apoptosis, while some members of the Bcl-2 family of proteins inhibit apoptosis. German scientist Karl Vogt was first to describe the principle of apoptosis in 1842, in 1885, anatomist Walther Flemming delivered a more precise description of the process of programmed cell death. However, it was not until 1965 that the topic was resurrected, while studying tissues using electron microscopy, John Foxton Ross Kerr at University of Queensland was able to distinguish apoptosis from traumatic cell death. Following the publication of a paper describing the phenomenon, Kerr was invited to join Alastair R Currie, as well as Andrew Wyllie, in 1972, the trio published a seminal article in the British Journal of Cancer. Kerr had initially used the term programmed cell necrosis, but in the article, Kerr, Wyllie and Currie credited James Cormack, a professor of Greek language at University of Aberdeen, with suggesting the term apoptosis. Kerr received the Paul Ehrlich and Ludwig Darmstaedter Prize on March 14,2000 and he shared the prize with Boston biologist H. Robert Horvitz. For many years, the apoptosis and programmed cell death were not highly cited. The 2002 Nobel Prize in Medicine was awarded to Sydney Brenner, Horvitz, the genes were identified by studies in the nematode C. elegans and homologues of these genes function in humans to regulate apoptosis. In Greek, apoptosis translates to the falling off of leaves from a tree, Cormack, professor of Greek language, reintroduced the term for medical use as it had a medical meaning for the Greeks over two thousand years before. Hippocrates used the term to mean the falling off of the bones, galen extended its meaning to the dropping of the scabs
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Cephalopod
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A cephalopod is any member of the molluscan class Cephalopoda. These exclusively marine animals are characterized by bilateral body symmetry, a prominent head, fishermen sometimes call them inkfish, referring to their common ability to squirt ink. The study of cephalopods is a branch of known as teuthology. Cephalopods became dominant during the Ordovician period, represented by primitive nautiloids, the class now contains two, only distantly related, extant subclasses, Coleoidea, which includes octopuses, squid, and cuttlefish, and Nautiloidea, represented by Nautilus and Allonautilus. In the Coleoidea, the shell has been internalized or is absent, whereas in the Nautiloidea. About 800 living species of cephalopods have been identified, two important extinct taxa are the Ammonoidea and Belemnoidea. There are over 800 extant species of cephalopod, although new species continue to be described, an estimated 11,000 extinct taxa have been described, although the soft-bodied nature of cephalopods means they are not easily fossilised. Cephalopods are found in all the oceans of Earth, none of them can tolerate freshwater, but the brief squid, Lolliguncula brevis, found in Chesapeake Bay, is a notable partial exception in that it tolerates brackish water. Cephalopods are thought to be unable to live in due to multiple biochemical constraints. Cephalopods occupy most of the depth of the ocean, from the plain to the sea surface. Their diversity is greatest near the equator and decreases towards the poles, Cephalopods are widely regarded as the most intelligent of the invertebrates, and have well developed senses and large brains. The nervous system of cephalopods is the most complex of the invertebrates, the brain is protected in a cartilaginous cranium. Cephalopods have also known to climb out of their aquaria, maneuver a distance of the lab floor, enter another aquarium to feed on the crabs. Cephalopods are social creatures, when isolated from their own kind, some cephalopods are able to fly through the air for distances of up to 50 m. While cephalopods are not particularly aerodynamic, they achieve these impressive ranges by jet-propulsion, the animals spread their fins and tentacles to form wings and actively control lift force with body posture. Cephalopods have advanced vision, can detect gravity with statocysts, and have a variety of sense organs. Octopuses use their arms to explore their environment and can use them for depth perception, most cephalopods rely on vision to detect predators and prey, and to communicate with one another. Consequently, cephalopod vision is acute, training experiments have shown that the octopus can distinguish the brightness, size, shape
listen); from Greek: μέλας melas, "black, dark") is a broad term for a group of natural pigments found in most organisms. Melanin is produced by the oxidation of the amino acid tyrosine, followed by polymerization. The melanin pigments are produced in a specialized group of cells known as melanocytes.
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. doi:10.1111/j.1751-1097.2004.tb00012.x. PMID 15068035.
