94-476: Xylitol is a chemical compound with the formula C 5 H 12 O 5 , or HO(CH 2 )(CHOH) 3 (CH 2 )OH; specifically, one particular stereoisomer with that structural formula. It is a colorless or white crystalline solid. It is classified as a polyalcohol and a sugar alcohol , specifically an alditol . Of the common sugar alcohols, only sorbitol is more soluble in water. The name derives from Ancient Greek : ξύλον , xyl[on] 'wood', with
188-543: A Raney nickel catalyst. The conversion changes the sugar (xylose, an aldehyde ) into the primary alcohol , xylitol. Xylitol can also be obtained by industrial fermentation , but this methodology are not as economical as the acid hydrolysis/chromatography route described above. Fermentation is effected by bacteria, fungi, or yeast, especially Candida tropicalis . According to the US Department of Energy , xylitol production by fermentation from discarded biomass
282-424: A chemical compound ; the concept is most readily understood when considering pure chemical substances . It follows from their being composed of fixed proportions of two or more types of atoms that chemical compounds can be converted, via chemical reaction , into compounds or substances each having fewer atoms. A chemical formula is a way of expressing information about the proportions of atoms that constitute
376-473: A molecular mass of 5808 Da . The molecular formula of human insulin is C 257 H 383 N 65 O 77 S 6 . It is a combination of two peptide chains ( dimer ) named an A-chain and a B-chain, which are linked together by two disulfide bonds . The A-chain is composed of 21 amino acids, while the B-chain consists of 30 residues. The linking (interchain) disulfide bonds are formed at cysteine residues between
470-419: A solid-state reaction , or the electron transfer reaction of reactive metals with reactive non-metals, such as halogen gases. Ionic compounds typically have high melting and boiling points , and are hard and brittle . As solids they are almost always electrically insulating , but when melted or dissolved they become highly conductive , because the ions are mobilized. An intermetallic compound
564-472: A ... white Powder ... with Sulphur it will compose a blood-red and volatile Cinaber. And yet out of all these exotick Compounds, we may recover the very same running Mercury. Boyle used the concept of "corpuscles"—or "atomes", as he also called them—to explain how a limited number of elements could combine into a vast number of compounds: If we assigne to the Corpuscles, whereof each Element consists,
658-408: A 110 amino acid-long protein called "preproinsulin". Preproinsulin is translated directly into the rough endoplasmic reticulum (RER), where its signal peptide is removed by signal peptidase to form "proinsulin". As the proinsulin folds , opposite ends of the protein, called the "A-chain" and the "B-chain", are fused together with three disulfide bonds . Folded proinsulin then transits through
752-724: A basic health system . Insulin may have originated more than a billion years ago. The molecular origins of insulin go at least as far back as the simplest unicellular eukaryotes . Apart from animals, insulin-like proteins are also known to exist in fungi and protists . Insulin is produced by beta cells of the pancreatic islets in most vertebrates and by the Brockmann body in some teleost fish . Cone snails : Conus geographus and Conus tulipa , venomous sea snails that hunt small fish, use modified forms of insulin in their venom cocktails. The insulin toxin, closer in structure to fishes' than to snails' native insulin, slows down
846-541: A compound molecule, using the standard chemical symbols with numerical subscripts . Many chemical compounds have a unique CAS number identifier assigned by the Chemical Abstracts Service . Globally, more than 350,000 chemical compounds (including mixtures of chemicals) have been registered for production and use. The term "compound"—with a meaning similar to the modern—has been used at least since 1661 when Robert Boyle's The Sceptical Chymist
940-412: A continuous three-dimensional network, usually in a crystalline structure . Ionic compounds containing basic ions hydroxide (OH ) or oxide (O ) are classified as bases. Ionic compounds without these ions are also known as salts and can be formed by acid–base reactions . Ionic compounds can also be produced from their constituent ions by evaporation of their solvent , precipitation , freezing ,
1034-416: A day of xylitol can cause diarrhea ", tabletop sweeteners (as well as other products containing xylitol) are required to display the warning "Excessive consumption may induce laxative effects". Xylitol has 2.4 kilocalories of food energy per gram of xylitol (10 kilojoules per gram) according to U.S. and E.U. food-labeling regulations. The real value can vary, depending on metabolic factors. Primarily,
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#17327764190551128-2757: A different chemical composition by interaction with a second chemical compound via a chemical reaction . In this process, bonds between atoms are broken in both of the interacting compounds, and then bonds are reformed so that new associations are made between atoms. Schematically, this reaction could be described as AB + CD → AD + CB , where A, B, C, and D are each unique atoms; and AB, AD, CD, and CB are each unique compounds. Insulin 1A7F , 1AI0 , 1AIY , 1B9E , 1BEN , 1EV3 , 1EV6 , 1EVR , 1FU2 , 1FUB , 1G7A , 1G7B , 1GUJ , 1HIQ , 1HIS , 1HIT , 1HLS , 1HTV , 1HUI , 1IOG , 1IOH , 1J73 , 1JCA , 1JCO , 1K3M , 1KMF , 1LKQ , 1LPH , 1MHI , 1MHJ , 1MSO , 1OS3 , 1OS4 , 1Q4V , 1QIY , 1QIZ , 1QJ0 , 1RWE , 1SF1 , 1T1K , 1T1P , 1T1Q , 1TRZ , 1TYL , 1TYM , 1UZ9 , 1VKT , 1W8P , 1XDA , 1XGL , 1XW7 , 1ZEG , 1ZEH , 1ZNJ , 2AIY , 2C8Q , 2C8R , 2CEU , 2H67 , 2HH4 , 2HHO , 2HIU , 2JMN , 2JUM , 2JUU , 2JUV , 2JV1 , 2JZQ , 2K91 , 2K9R , 2KJJ , 2KJU , 2KQQ , 2KXK , 2L1Y , 2L1Z , 2LGB , 2M1D , 2M1E , 2M2M , 2M2N , 2M2O , 2M2P , 2OLY , 2OLZ , 2OM0 , 2OM1 , 2OMG , 2OMH , 2OMI , 2QIU , 2R34 , 2R35 , 2R36 , 2RN5 , 2VJZ , 2VK0 , 2W44 , 2WBY , 2WC0 , 2WRU , 2WRV , 2WRW , 2WRX , 2WS0 , 2WS1 , 2WS4 , 2WS6 , 2WS7 , 3AIY , 3BXQ , 3E7Y , 3E7Z , 3EXX , 3FQ9 , 3I3Z , 3I40 , 3ILG , 3INC , 3IR0 , 3Q6E , 3ROV , 3TT8 , 3U4N , 3UTQ , 3UTS , 3UTT , 3V19 , 3V1G , 3W11 , 3W12 , 3W13 , 3W7Y , 3W7Z , 3W80 , 3ZI3 , 3ZQR , 3ZS2 , 3ZU1 , 4AIY , 4AJX , 4AJZ , 4AK0 , 4AKJ , 4EFX , 4EWW , 4EWX , 4EWZ , 4EX0 , 4EX1 , 4EXX , 4EY1 , 4EY9 , 4EYD , 4EYN , 4EYP , 4F0N , 4F0O , 4F1A , 4F1B , 4F1C , 4F1D , 4F1F , 4F1G , 4F4T , 4F4V , 4F51 , 4F8F , 4FG3 , 4FKA , 4GBC , 4GBI , 4GBK , 4GBL , 4GBN , 4IUZ , 5AIY , 2LWZ , 3JSD , 3KQ6 , 3P2X , 3P33 , 1JK8 , 2MLI , 2MPG , 2MPI , 2MVC , 2MVD , 4CXL , 4CXN , 4CY7 , 4NIB , 4OGA , 4P65 , 4Q5Z , 4RXW , 4UNE , 4UNG , 4UNH , 4XC4 , 4WDI , 4Z76 , 4Z77 , 4Z78 , 2N2W , 5CO6 , 5ENA , 4Y19 , 5BQQ , 5BOQ , 2N2V , 5CNY , 5CO9 , 5EN9 , 4Y1A , 2N2X , 5BPO , 5CO2 , 5BTS , 5HYJ , 5C0D ,%%s 1EFE , 1SJT , 1SJU , 2KQP ,%%s 1T0C ,%%s 2G54 , 2G56 , 3HYD , 2OMQ 3630 16334 ENSG00000254647 ENSMUSG00000000215 P01308 P01326 NM_000207 NM_001185097 NM_001185098 NM_001291897 NM_001185083 NM_001185084 NM_008387 NP_001172026.1 NP_001172027.1 NP_001278826.1 NP_000198 NP_000198 NP_000198 NP_000198 NP_001172012 NP_001172013 NP_032413 Insulin ( / ˈ ɪ n . sj ʊ . l ɪ n / , from Latin insula , 'island')
1222-417: A glucose load (75 or 100 g of glucose), followed by a slow drop over the next 100 minutes, to remain above 120 mg/100 mL after two hours after the start of the test. In a normal person the blood glucose level is corrected (and may even be slightly over-corrected) by the end of the test. An insulin spike is a 'first response' to blood glucose increase, this response is individual and dose specific although it
1316-566: A particular chemical compound, using chemical symbols for the chemical elements, and subscripts to indicate the number of atoms involved. For example, water is composed of two hydrogen atoms bonded to one oxygen atom: the chemical formula is H 2 O. In the case of non-stoichiometric compounds , the proportions may be reproducible with regard to their preparation, and give fixed proportions of their component elements, but proportions that are not integral [e.g., for palladium hydride , PdH x (0.02 < x < 0.58)]. Chemical compounds have
1410-801: A peculiar size and shape ... such ... Corpuscles may be mingled in such various Proportions, and ... connected so many ... wayes, that an almost incredible number of ... Concretes may be compos’d of them. In his Logick , published in 1724, the English minister and logician Isaac Watts gave an early definition of chemical element, and contrasted element with chemical compound in clear, modern terms. Among Substances, some are called Simple, some are Compound ... Simple Substances ... are usually called Elements, of which all other Bodies are compounded: Elements are such Substances as cannot be resolved, or reduced, into two or more Substances of different Kinds. ... Followers of Aristotle made Fire, Air, Earth and Water to be
1504-402: A plane of symmetry. Industrial production starts with lignocellulosic biomass from which xylan is extracted; raw biomass materials include hardwoods , softwoods , and agricultural waste from processing maize, wheat, or rice. The mixture is hydrolyzed with acid to give xylose . The xylose is purified by chromatography . Purified xylose is catalytically hydrogenated into xylitol using
1598-461: A positive effect in reducing tooth decay of xylitol-containing fluoride toothpastes when compared to fluoride-only toothpaste, but there was insufficient evidence to determine whether other xylitol-containing products can prevent tooth decay in infants, children or adults. Subsequent reviews support the belief that xylitol can suppress the growth of pathogenic Streptococcus in the mouth, thereby reducing dental caries and gingivitis , although there
1692-496: A positively charged cation . The nonmetal will gain the electrons from the metal, making the nonmetal a negatively charged anion . As outlined, ionic bonds occur between an electron donor, usually a metal, and an electron acceptor, which tends to be a nonmetal. Hydrogen bonding occurs when a hydrogen atom bonded to an electronegative atom forms an electrostatic connection with another electronegative atom through interacting dipoles or charges. A compound can be converted to
1786-447: A solid state dependent on how low the temperature of the environment is. A covalent bond , also known as a molecular bond, involves the sharing of electrons between two atoms. Primarily, this type of bond occurs between elements that fall close to each other on the periodic table of elements , yet it is observed between some metals and nonmetals. This is due to the mechanism of this type of bond. Elements that fall close to each other on
1880-757: A syrup may have a moderate effect in preventing AOM in healthy children. It may be an alternative to conventional therapies (such as antibiotics ) to lower risk of earache in healthy children – reducing risk of occurrence by 25% – although there is no definitive proof that it could be used as a therapy for earache. In 2011, EFSA approved a marketing claim that foods or beverages containing xylitol or similar sugar replacers cause lower blood glucose and lower insulin responses compared to sugar-containing foods or drinks. Xylitol products are used as sucrose substitutes for weight control, as xylitol has 40% fewer calories than sucrose (2.4 kcal/g compared to 4.0 kcal/g for sucrose). The glycemic index (GI) of xylitol
1974-448: A transcription factor for MafA in an unknown manner and MafA is transported out of the cell. MafA is then translocated back into the nucleus where it binds the C1 element of the insulin promoter. These transcription factors work synergistically and in a complex arrangement. Increased blood glucose can after a while destroy the binding capacities of these proteins, and therefore reduce
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#17327764190552068-469: A unique and defined chemical structure held together in a defined spatial arrangement by chemical bonds . Chemical compounds can be molecular compounds held together by covalent bonds , salts held together by ionic bonds , intermetallic compounds held together by metallic bonds , or the subset of chemical complexes that are held together by coordinate covalent bonds . Pure chemical elements are generally not considered chemical compounds, failing
2162-416: Is strongly conserved and varies only slightly between species. Bovine insulin differs from human in only three amino acid residues, and porcine insulin in one. Even insulin from some species of fish is similar enough to human to be clinically effective in humans. Insulin in some invertebrates is quite similar in sequence to human insulin, and has similar physiological effects. The strong homology seen in
2256-541: Is a chemical substance composed of many identical molecules (or molecular entities ) containing atoms from more than one chemical element held together by chemical bonds . A molecule consisting of atoms of only one element is therefore not a compound. A compound can be transformed into a different substance by a chemical reaction , which may involve interactions with other substances. In this process, bonds between atoms may be broken and/or new bonds formed. There are four major types of compounds, distinguished by how
2350-399: Is a peptide hormone produced by beta cells of the pancreatic islets encoded in humans by the insulin ( INS) gene . It is the main anabolic hormone of the body. It regulates the metabolism of carbohydrates , fats , and protein by promoting the absorption of glucose from the blood into cells of the liver , fat , and skeletal muscles . In these tissues the absorbed glucose
2444-519: Is a common first symptom, which can be followed by tiredness and ataxia . At doses above 500 mg/kg bw, liver failure is likely and may result in coagulopathies like disseminated intravascular coagulation . Xylitol is safe for rhesus macaques , horses , and rats . A 2018 study suggests that xylitol is safe for cats in doses of up to 1000 mg/kg; however, this study was performed on only 6 cats and should not be considered definitive. Chemical compound A chemical compound
2538-403: Is a type of metallic alloy that forms an ordered solid-state compound between two or more metallic elements. Intermetallics are generally hard and brittle, with good high-temperature mechanical properties. They can be classified as stoichiometric or nonstoichiometric intermetallic compounds. A coordination complex consists of a central atom or ion, which is usually metallic and is called
2632-546: Is also regulated by glucose: high glucose promotes insulin production while low glucose levels lead to lower production. Insulin enhances glucose uptake and metabolism in the cells, thereby reducing blood sugar. Their neighboring alpha cells , by taking their cues from the beta cells, secrete glucagon into the blood in the opposite manner: increased secretion when blood glucose is low, and decreased secretion when glucose concentrations are high. Glucagon increases blood glucose by stimulating glycogenolysis and gluconeogenesis in
2726-478: Is approved as a food additive and sugar substitute in the United States. Xylitol is often marketed as "birch sugar". Xylitol is also found as an additive to saline solution for nasal irrigation and has been reported to be effective in improving symptoms of chronic sinusitis . Xylitol can also be incorporated into fabrics to produce a cooling fabric. When moisture, such as sweat, comes into contact with
2820-486: Is as follows: This is the primary mechanism for release of insulin. Other substances known to stimulate insulin release include the amino acids arginine and leucine, parasympathetic release of acetylcholine (acting via the phospholipase C pathway), sulfonylurea , cholecystokinin (CCK, also via phospholipase C), and the gastrointestinally derived incretins , such as glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic peptide (GIP). Release of insulin
2914-699: Is characterized by increased glucagon secretion which is unaffected by, and unresponsive to the concentration of blood glucose. But insulin is still secreted into the blood in response to the blood glucose. As a result, glucose accumulates in the blood. The human insulin protein is composed of 51 amino acids , and has a molecular mass of 5808 Da . It is a hetero dimer of an A-chain and a B-chain, which are linked together by disulfide bonds . Insulin's structure varies slightly between species of animals. Insulin from non-human animal sources differs somewhat in effectiveness (in carbohydrate metabolism effects) from human insulin because of these variations. Porcine insulin
Xylitol - Misplaced Pages Continue
3008-427: Is concern that swallowed xylitol may cause intestinal dysbiosis . A 2022 review suggested that xylitol-containing chewing gum decreases plaque, but not xylitol-containing candy. In 2011 EFSA "concluded that there was not enough evidence to support" the claim that xylitol-sweetened gum could prevent middle-ear infections, also known as acute otitis media (AOM). A 2016 review indicated that xylitol in chewing gum or
3102-768: Is considered to be safe for humans. Xylitol can be toxic to dogs . Emil Fischer , a German chemistry professor, and his assistant Rudolf Stahel isolated a new compound from beech wood chips in September 1890 and named it Xylit , the German word for xylitol. The following year, the French chemist M. G. Bertrand isolated xylitol syrup by processing wheat and oat straw. Sugar rationing during World War II led to an interest in sugar substitutes . Interest in xylitol and other polyols became intense, leading to their characterization and manufacturing methods. Xylitol
3196-404: Is converted into either glycogen , via glycogenesis , or fats ( triglycerides ), via lipogenesis ; in the liver, glucose is converted into both. Glucose production and secretion by the liver are strongly inhibited by high concentrations of insulin in the blood. Circulating insulin also affects the synthesis of proteins in a wide variety of tissues. It is thus an anabolic hormone, promoting
3290-504: Is especially close to the human version, and was widely used to treat type 1 diabetics before human insulin could be produced in large quantities by recombinant DNA technologies. Insulin was the first peptide hormone discovered. Frederick Banting and Charles Best , working in the laboratory of John Macleod at the University of Toronto , were the first to isolate insulin from dog pancreas in 1921. Frederick Sanger sequenced
3384-492: Is far more stable than the monomer, which is desirable for practical reasons; however, the monomer is a much faster-reacting drug because diffusion rate is inversely related to particle size. A fast-reacting drug means insulin injections do not have to precede mealtimes by hours, which in turn gives people with diabetes more flexibility in their daily schedules. Insulin can aggregate and form fibrillar interdigitated beta-sheets . This can cause injection amyloidosis , and prevents
3478-399: Is inhibition due to dominance of the α-adrenergic receptors. When the glucose level comes down to the usual physiologic value, insulin release from the β-cells slows or stops. If the blood glucose level drops lower than this, especially to dangerously low levels, release of hyperglycemic hormones (most prominently glucagon from islet of Langerhans alpha cells) forces release of glucose into
3572-415: Is known as a homodimer. Insulin binds to the α-subunits of the homodimer, which faces the extracellular side of the cells. The β subunits have tyrosine kinase enzyme activity which is triggered by the insulin binding. This activity provokes the autophosphorylation of the β subunits and subsequently the phosphorylation of proteins inside the cell known as insulin receptor substrates (IRS). The phosphorylation of
3666-453: Is located in the nuclear periphery as a result of interaction with HDAC1 and 2 , which results in downregulation of insulin secretion. An increase in blood glucose levels causes phosphorylation of PDX1 , which leads it to undergo nuclear translocation and bind the A3 element within the insulin promoter. Upon translocation it interacts with coactivators HAT p300 and SETD7 . PDX1 affects
3760-460: Is missing an intron ( Ins1 ). Transcription of the insulin gene increases in response to elevated blood glucose. This is primarily controlled by transcription factors that bind enhancer sequences in the ~400 base pairs before the gene's transcription start site. The major transcription factors influencing insulin secretion are PDX1 , NeuroD1 , and MafA . During a low-glucose state, PDX1 (pancreatic and duodenal homeobox protein 1)
3854-493: Is neutral overall, but consists of positively charged ions called cations and negatively charged ions called anions . These can be simple ions such as the sodium (Na ) and chloride (Cl ) in sodium chloride , or polyatomic species such as the ammonium ( NH 4 ) and carbonate ( CO 3 ) ions in ammonium carbonate . Individual ions within an ionic compound usually have multiple nearest neighbours, so are not considered to be part of molecules, but instead part of
Xylitol - Misplaced Pages Continue
3948-434: Is one of the most valuable renewable chemicals for commerce, forecast to be a US $ 1.4 billion industry by 2025. Xylitol is used as a sugar substitute in such manufactured products as drugs , dietary supplements , confections , toothpaste , and chewing gum , but is not a common household sweetener. Xylitol has negligible effects on blood sugar because its assimilation and metabolism are independent of insulin . It
4042-484: Is one of three 5-carbon sugar alcohols. The others are arabitol and ribitol . These three compounds differ in the stereochemistry of the three secondary alcohol groups. Xylitol occurs naturally in small amounts in plums, strawberries, cauliflower, and pumpkin; humans and many other animals make trace amounts during metabolism of carbohydrates . Unlike most sugar alcohols, xylitol is achiral . Most other isomers of pentane-1,2,3,4,5-pentol are chiral, but xylitol has
4136-800: Is only 7% of the GI for glucose . When ingested at high doses, xylitol and other polyols may cause gastrointestinal discomfort, including flatulence , diarrhea , and irritable bowel syndrome (see Metabolism above); some people experience the adverse effects at lower doses. Xylitol has a lower laxation threshold than some sugar alcohols but is more easily tolerated than mannitol and sorbitol . Increased xylitol consumption can increase oxalate, calcium, and phosphate excretion to urine (termed oxaluria , calciuria , and phosphaturia , respectively). These are known risk factors for kidney stone disease , but despite that, xylitol has not been linked to kidney disease in humans. A 2024 study suggests that xylitol
4230-533: Is packaged inside mature granules waiting for metabolic signals (such as leucine, arginine, glucose and mannose) and vagal nerve stimulation to be exocytosed from the cell into the circulation. Insulin and its related proteins have been shown to be produced inside the brain, and reduced levels of these proteins are linked to Alzheimer's disease. Insulin release is stimulated also by beta-2 receptor stimulation and inhibited by alpha-1 receptor stimulation. In addition, cortisol, glucagon and growth hormone antagonize
4324-491: Is prothrombotic (increases clotting) and is associated with cardiovascular risk when consumed at "typical dietary amounts". Xylitol is poisonous to dogs . Ingesting 100 milligrams of xylitol per kilogram of body weight (mg/kg bw) causes dogs to experience a dose-dependent insulin release; depending on the dose it can result in life-threatening hypoglycemia . Hypoglycemic symptoms of xylitol toxicity may arise as quickly as 30 to 60 minutes after ingestion. Vomiting
4418-494: Is strongly inhibited by norepinephrine (noradrenaline), which leads to increased blood glucose levels during stress. It appears that release of catecholamines by the sympathetic nervous system has conflicting influences on insulin release by beta cells, because insulin release is inhibited by α 2 -adrenergic receptors and stimulated by β 2 -adrenergic receptors. The net effect of norepinephrine from sympathetic nerves and epinephrine from adrenal glands on insulin release
4512-418: Is the presence of zinc atoms (Zn ) on the axis of symmetry, which are surrounded by three water molecules and three histidine residues at position B10. The hexamer is an inactive form with long-term stability, which serves as a way to keep the highly reactive insulin protected, yet readily available. The hexamer-monomer conversion is one of the central aspects of insulin formulations for injection. The hexamer
4606-563: The Golgi apparatus and is packaged into specialized secretory vesicles . In the granule, proinsulin is cleaved by proprotein convertase 1/3 and proprotein convertase 2 , removing the middle part of the protein, called the " C-peptide ". Finally, carboxypeptidase E removes two pairs of amino acids from the protein's ends, resulting in active insulin – the insulin A- and B- chains, now connected with two disulfide bonds. The resulting mature insulin
4700-452: The coordination centre , and a surrounding array of bound molecules or ions, that are in turn known as ligands or complexing agents. Many metal-containing compounds, especially those of transition metals , are coordination complexes. A coordination complex whose centre is a metal atom is called a metal complex of d block element. Compounds are held together through a variety of different types of bonding and forces. The differences in
4794-457: The histone modifications through acetylation and deacetylation as well as methylation . It is also said to suppress glucagon . NeuroD1 , also known as β2, regulates insulin exocytosis in pancreatic β cells by directly inducing the expression of genes involved in exocytosis. It is localized in the cytosol , but in response to high glucose it becomes glycosylated by OGT and/or phosphorylated by ERK , which causes translocation to
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#17327764190554888-449: The oxygen molecule (O 2 ); or it may be heteronuclear , a chemical compound composed of more than one element, as with water (two hydrogen atoms and one oxygen atom; H 2 O). A molecule is the smallest unit of a substance that still carries all the physical and chemical properties of that substance. An ionic compound is a chemical compound composed of ions held together by electrostatic forces termed ionic bonding . The compound
4982-463: The Earth. Other compounds regarded as chemically identical may have varying amounts of heavy or light isotopes of the constituent elements, which changes the ratio of elements by mass slightly. A molecule is an electrically neutral group of two or more atoms held together by chemical bonds. A molecule may be homonuclear , that is, it consists of atoms of one chemical element, as with two atoms in
5076-533: The IRS activates a signal transduction cascade that leads to the activation of other kinases as well as transcription factors that mediate the intracellular effects of insulin. The cascade that leads to the insertion of GLUT4 glucose transporters into the cell membranes of muscle and fat cells, and to the synthesis of glycogen in liver and muscle tissue, as well as the conversion of glucose into triglycerides in liver, adipose, and lactating mammary gland tissue, operates via
5170-534: The Truth ;; tho' they are not all agreed ... Compound Substances are made up of two or more simple Substances ... So a Needle is simple Body, being made only of Steel; but a Sword or a Knife is a compound because its ... Handle is made of Materials different from the Blade. Any substance consisting of two or more different types of atoms ( chemical elements ) in a fixed stoichiometric proportion can be termed
5264-404: The actions of insulin during times of stress. Insulin also inhibits fatty acid release by hormone-sensitive lipase in adipose tissue. Contrary to an initial belief that hormones would be generally small chemical molecules, as the first peptide hormone known of its structure, insulin was found to be quite large. A single protein (monomer) of human insulin is composed of 51 amino acids , and has
5358-487: The activation, by IRS-1, of phosphoinositol 3 kinase ( PI3K ). This enzyme converts a phospholipid in the cell membrane by the name of phosphatidylinositol 4,5-bisphosphate (PIP2), into phosphatidylinositol 3,4,5-triphosphate (PIP3), which, in turn, activates protein kinase B (PKB). Activated PKB facilitates the fusion of GLUT4 containing endosomes with the cell membrane, resulting in an increase in GLUT4 transporters in
5452-459: The acute thermoregulatory and glucoregulatory response to food intake, suggesting that central nervous insulin contributes to the co-ordination of a wide variety of homeostatic or regulatory processes in the human body. Insulin also has stimulatory effects on gonadotropin-releasing hormone from the hypothalamus , thus favoring fertility . Once an insulin molecule has docked onto the receptor and effected its action, it may be released back into
5546-462: The amino acid structure in 1951, which made insulin the first protein to be fully sequenced. The crystal structure of insulin in the solid state was determined by Dorothy Hodgkin in 1969. Insulin is also the first protein to be chemically synthesised and produced by DNA recombinant technology . It is on the WHO Model List of Essential Medicines , the most important medications needed in
5640-403: The amount of insulin secreted, causing diabetes . The decreased binding activities can be mediated by glucose induced oxidative stress and antioxidants are said to prevent the decreased insulin secretion in glucotoxic pancreatic β cells . Stress signalling molecules and reactive oxygen species inhibits the insulin gene by interfering with the cofactors binding the transcription factors and
5734-415: The blood from the liver glycogen stores, supplemented by gluconeogenesis if the glycogen stores become depleted. By increasing blood glucose, the hyperglycemic hormones prevent or correct life-threatening hypoglycemia. Evidence of impaired first-phase insulin release can be seen in the glucose tolerance test , demonstrated by a substantially elevated blood glucose level at 30 minutes after the ingestion of
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#17327764190555828-517: The blood. In type 2 diabetes , the destruction of beta cells is less pronounced than in type 1, and is not due to an autoimmune process. Instead, there is an accumulation of amyloid in the pancreatic islets, which likely disrupts their anatomy and physiology. The pathogenesis of type 2 diabetes is not well understood but reduced population of islet beta-cells, reduced secretory function of islet beta-cells that survive, and peripheral tissue insulin resistance are known to be involved. Type 2 diabetes
5922-431: The constituent atoms are bonded together. Molecular compounds are held together by covalent bonds ; ionic compounds are held together by ionic bonds ; intermetallic compounds are held together by metallic bonds ; coordination complexes are held together by coordinate covalent bonds . Non-stoichiometric compounds form a disputed marginal case. A chemical formula specifies the number of atoms of each element in
6016-417: The conversion of small molecules in the blood into large molecules in the cells. Low insulin in the blood has the opposite effect, promoting widespread catabolism , especially of reserve body fat . Beta cells are sensitive to blood sugar levels so that they secrete insulin into the blood in response to high level of glucose, and inhibit secretion of insulin when glucose levels are low. Insulin production
6110-429: The enzymes controlling the rate of glycolysis leading to the synthesis of fats via malonyl-CoA in the tissues that can generate triglycerides , and also the enzymes that control the rate of gluconeogenesis in the liver. The overall effect of these final enzyme dephosphorylations is that, in the tissues that can carry out these reactions, glycogen and fat synthesis from glucose are stimulated, and glucose production by
6204-456: The extracellular environment, or it may be degraded by the cell. The two primary sites for insulin clearance are the liver and the kidney. It is broken down by the enzyme, protein-disulfide reductase (glutathione) , which breaks the disulphide bonds between the A and B chains. The liver clears most insulin during first-pass transit, whereas the kidney clears most of the insulin in systemic circulation. Degradation normally involves endocytosis of
6298-430: The first phase of insulin exocytosis, most of the granules predispose for exocytosis are released after the calcium internalization. This pool is known as Readily Releasable Pool (RRP). The RRP granules represent 0.3-0.7% of the total insulin-containing granule population, and they are found immediately adjacent to the plasma membrane. During the second phase of exocytosis, insulin granules require mobilization of granules to
6392-400: The fixed ratios. Many solid chemical substances—for example many silicate minerals —are chemical substances, but do not have simple formulae reflecting chemically bonding of elements to one another in fixed ratios; even so, these crystalline substances are often called " non-stoichiometric compounds ". It may be argued that they are related to, rather than being chemical compounds, insofar as
6486-513: The four Elements, of which all earthly Things were compounded; and they suppos'd the Heavens to be a Quintessence, or fifth sort of Body, distinct from all these : But, since experimental Philosophy ... have been better understood, this Doctrine has been abundantly refuted. The Chymists make Spirit, Salt, Sulphur, Water and Earth to be their five Elements, because they can reduce all terrestrial Things to these five : This seems to come nearer
6580-535: The freezing point of the mixture. No serious health risk exists in most humans for normal levels of consumption. The European Food Safety Authority has not set a limit on daily intake of xylitol. Due to the adverse laxative effect that all polyols have on the digestive system in high doses, xylitol is banned from soft drinks in the European Union . Similarly, due to a 1985 report by the E.U. Scientific Committee on Food which states that "ingesting 50 g
6674-408: The global human metabolism level include: The actions of insulin (indirect and direct) on cells include: Insulin also influences other body functions, such as vascular compliance and cognition . Once insulin enters the human brain, it enhances learning and memory and benefits verbal memory in particular. Enhancing brain insulin signaling by means of intranasal insulin administration also enhances
6768-518: The insulin sequence of diverse species suggests that it has been conserved across much of animal evolutionary history. The C-peptide of proinsulin , however, differs much more among species; it is also a hormone, but a secondary one. Insulin is produced and stored in the body as a hexamer (a unit of six insulin molecules), while the active form is the monomer. The hexamer is about 36000 Da in size. The six molecules are linked together as three dimeric units to form symmetrical molecule. An important feature
6862-715: The intestines. Of the remaining 50% that is not absorbed by the intestines, in humans, 50–75% of the xylitol remaining in the gut is fermented by gut bacteria into short-chain organic acids and gases, which may produce flatulence . The remnant unabsorbed xylitol that escapes fermentation is excreted unchanged, mostly in feces; less than 2 g of xylitol out of every 100 g ingested is excreted via urine. Xylitol ingestion also increases motilin secretion, which may be related to xylitol's ability to cause diarrhea. The less-digestible but fermentable nature of xylitol also contributes to constipation relieving effects. A 2015 Cochrane review of ten studies between 1991 and 2014 suggested
6956-428: The liver in extracting insulin from the blood. This oscillation is important to consider when administering insulin-stimulating medication, since it is the oscillating blood concentration of insulin release, which should, ideally, be achieved, not a constant high concentration. This may be achieved by delivering insulin rhythmically to the portal vein , by light activated delivery, or by islet cell transplantation to
7050-401: The liver metabolizes absorbed xylitol. The main metabolic route in humans occurs in cytoplasm , via nonspecific NAD -dependent dehydrogenase (polyol dehydrogenase), which transforms xylitol to D -xylulose . Specific xylulokinase phosphorylates it to D -xylulose-5-phosphate . This then goes to pentose phosphate pathway for further processing. About 50% of eaten xylitol is absorbed via
7144-413: The liver through glycogenolysis and gluconeogenesis are inhibited. The breakdown of triglycerides by adipose tissue into free fatty acids and glycerol is also inhibited. After the intracellular signal that resulted from the binding of insulin to its receptor has been produced, termination of signaling is then needed. As mentioned below in the section on degradation, endocytosis and degradation of
7238-465: The liver. The blood insulin level can be measured in international units , such as μIU/mL or in molar concentration , such as pmol/L, where 1 μIU/mL equals 6.945 pmol/L. A typical blood level between meals is 8–11 μIU/mL (57–79 pmol/L). The effects of insulin are initiated by its binding to a receptor, the insulin receptor (IR) , present in the cell membrane. The receptor molecule contains an α- and β subunits. Two molecules are joined to form what
7332-464: The liver. The secretion of insulin and glucagon into the blood in response to the blood glucose concentration is the primary mechanism of glucose homeostasis . Decreased or absent insulin activity results in diabetes , a condition of high blood sugar level ( hyperglycaemia ). There are two types of the disease. In type 1 diabetes , the beta cells are destroyed by an autoimmune reaction so that insulin can no longer be synthesized or be secreted into
7426-471: The nucleus. In the nucleus β2 heterodimerizes with E47 , binds to the E1 element of the insulin promoter and recruits co-activator p300 which acetylates β2. It is able to interact with other transcription factors as well in activation of the insulin gene. MafA is degraded by proteasomes upon low blood glucose levels. Increased levels of glucose make an unknown protein glycosylated . This protein works as
7520-536: The periodic table tend to have similar electronegativities , which means they have a similar affinity for electrons. Since neither element has a stronger affinity to donate or gain electrons, it causes the elements to share electrons so both elements have a more stable octet . Ionic bonding occurs when valence electrons are completely transferred between elements. Opposite to covalent bonding, this chemical bond creates two oppositely charged ions. The metals in ionic bonding usually lose their valence electrons, becoming
7614-613: The plasma membrane and a previous preparation to undergo their release. Thus, the second phase of insulin release is governed by the rate at which granules get ready for release. This pool is known as a Reserve Pool (RP). The RP is released slower than the RRP (RRP: 18 granules/min; RP: 6 granules/min). Reduced first-phase insulin release may be the earliest detectable beta cell defect predicting onset of type 2 diabetes . First-phase release and insulin sensitivity are independent predictors of diabetes. The description of first phase release
7708-402: The plasma membrane. PKB also phosphorylates glycogen synthase kinase (GSK), thereby inactivating this enzyme. This means that its substrate, glycogen synthase (GS), cannot be phosphorylated, and remains dephosphorylated, and therefore active. The active enzyme, glycogen synthase (GS), catalyzes the rate limiting step in the synthesis of glycogen from glucose. Similar dephosphorylations affect
7802-497: The positions A7-B7 and A20-B19. There is an additional (intrachain) disulfide bond within the A-chain between cysteine residues at positions A6 and A11. The A-chain exhibits two α-helical regions at A1-A8 and A12-A19 which are antiparallel; while the B chain has a central α -helix (covering residues B9-B19) flanked by the disulfide bond on either sides and two β-sheets (covering B7-B10 and B20-B23). The amino acid sequence of insulin
7896-538: The prey fishes by lowering their blood glucose levels. Insulin is produced exclusively in the beta cells of the pancreatic islets in mammals, and the Brockmann body in some fish. Human insulin is produced from the INS gene , located on chromosome 11. Rodents have two functional insulin genes; one is the homolog of most mammalian genes ( Ins2 ), and the other is a retroposed copy that includes promoter sequence but that
7990-461: The receptor bound to insulin is a main mechanism to end signaling. In addition, the signaling pathway is also terminated by dephosphorylation of the tyrosine residues in the various signaling pathways by tyrosine phosphatases. Serine/Threonine kinases are also known to reduce the activity of insulin. The structure of the insulin– insulin receptor complex has been determined using the techniques of X-ray crystallography . The actions of insulin on
8084-496: The storage of insulin for long periods. Beta cells in the islets of Langerhans release insulin in two phases. The first-phase release is rapidly triggered in response to increased blood glucose levels, and lasts about 10 minutes. The second phase is a sustained, slow release of newly formed vesicles triggered independently of sugar, peaking in 2 to 3 hours. The two phases of the insulin release suggest that insulin granules are present in diverse stated populations or "pools". During
8178-401: The suffix -itol used to denote it being a sugar alcohol. Xylitol is used as a food additive and sugar substitute . Its European Union code number is E967 . Replacing sugar with xylitol in food products may promote better dental health, but evidence is lacking on whether xylitol itself prevents dental cavities . In the United States, xylitol is used as a common sugar substitute , and
8272-463: The transcription factors itself. Several regulatory sequences in the promoter region of the human insulin gene bind to transcription factors . In general, the A-boxes bind to Pdx1 factors, E-boxes bind to NeuroD , C-boxes bind to MafA , and cAMP response elements to CREB . There are also silencers that inhibit transcription. Insulin is synthesized as an inactive precursor molecule,
8366-494: The two or more atom requirement, though they often consist of molecules composed of multiple atoms (such as in the diatomic molecule H 2 , or the polyatomic molecule S 8 , etc.). Many chemical compounds have a unique numerical identifier assigned by the Chemical Abstracts Service (CAS): its CAS number . There is varying and sometimes inconsistent nomenclature differentiating substances, which include truly non-stoichiometric examples, from chemical compounds, which require
8460-455: The types of bonds in compounds differ based on the types of elements present in the compound. London dispersion forces are the weakest force of all intermolecular forces . They are temporary attractive forces that form when the electrons in two adjacent atoms are positioned so that they create a temporary dipole . Additionally, London dispersion forces are responsible for condensing non polar substances to liquids, and to further freeze to
8554-421: The variability in their compositions is often due to either the presence of foreign elements trapped within the crystal structure of an otherwise known true chemical compound , or due to perturbations in structure relative to the known compound that arise because of an excess of deficit of the constituent elements at places in its structure; such non-stoichiometric substances form most of the crust and mantle of
8648-491: The xylitol embedded in the fabric, it produces a cooling sensation. Humans absorb xylitol more slowly than sucrose, and xylitol supplies 40% fewer calories than an equal mass of sucrose. Xylitol has about the same sweetness as sucrose , but is sweeter than similar compounds like sorbitol and mannitol . Xylitol is stable enough to be used in baking, but because xylitol and other polyols are more heat-stable, they do not caramelise as sugars do. When used in foods, they lower
8742-456: Was always previously assumed to be food type specific only. Even during digestion, in general, one or two hours following a meal, insulin release from the pancreas is not continuous, but oscillates with a period of 3–6 minutes, changing from generating a blood insulin concentration more than about 800 p mol /l to less than 100 pmol/L (in rats). This is thought to avoid downregulation of insulin receptors in target cells, and to assist
8836-409: Was published. In this book, Boyle variously used the terms "compound", "compounded body", "perfectly mixt body", and "concrete". "Perfectly mixt bodies" included for example gold, lead, mercury, and wine. While the distinction between compound and mixture is not so clear, the distinction between element and compound is a central theme. Quicksilver ... with Aqua fortis will be brought into
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