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73-569: Though unlikely to be harmful over the short term, Master Cleanse and similar programs can be harmful over the long term. The diet lacks protein, fatty acids, and other essential nutrients and depends entirely on carbohydrates for calories. The daily laxative regimen can cause electrolyte imbalances and disrupt the normal gastrointestinal microbiome . In the longer run, staying on the Master Cleanse diet could result in severe metabolic acidosis , which can lead to coma or death. The Master Cleanse diet

146-401: A covalent bond known as a glycosidic linkage formed via a dehydration reaction , resulting in the loss of a hydrogen atom from one monosaccharide and a hydroxyl group from the other. The formula of unmodified disaccharides is C 12 H 22 O 11 . Although there are numerous kinds of disaccharides, a handful of disaccharides are particularly notable. Sucrose , pictured to the right,

219-413: A balanced diet that includes six one-ounce servings of grain foods each day, at least half from whole grain sources and the rest are from enriched . The glycemic index (GI) and glycemic load concepts have been developed to characterize food behavior during human digestion. They rank carbohydrate-rich foods based on the rapidity and magnitude of their effect on blood glucose levels. Glycemic index

292-517: A component of DNA , is a modified version of ribose ; chitin is composed of repeating units of N-acetyl glucosamine , a nitrogen -containing form of glucose. Carbohydrates are polyhydroxy aldehydes, ketones, alcohols, acids, their simple derivatives and their polymers having linkages of the acetal type. They may be classified according to their degree of polymerization , and may be divided initially into three principal groups, namely sugars, oligosaccharides and polysaccharides. Monosaccharides are

365-399: A form of carbohydrate storage in animal livers, was discovered by French physiologist Claude Bernard . Formerly the name "carbohydrate" was used in chemistry for any compound with the formula C m (H 2 O) n . Following this definition, some chemists considered formaldehyde (CH 2 O) to be the simplest carbohydrate, while others claimed that title for glycolaldehyde . Today,

438-467: A goal of 55–75% of total energy from carbohydrates, but only 10% directly from sugars (their term for simple carbohydrates). A 2017 Cochrane Systematic Review concluded that there was insufficient evidence to support the claim that whole grain diets can affect cardiovascular disease. Nutritionists often refer to carbohydrates as either simple or complex. However, the exact distinction between these groups can be ambiguous. The term complex carbohydrate

511-474: A marine animal with a protective shell. The structure of chitin was determined by Albert Hofmann in 1929. Hofmann hydrolyzed chitin using a crude preparation of the enzyme chitinase, which he obtained from the snail Helix pomatia . Chitin is a modified polysaccharide that contains nitrogen; it is synthesized from units of N -acetyl- D -glucosamine (to be precise, 2-(acetylamino)-2-deoxy- D -glucose). These units form covalent β-(1→4)-linkages (like

584-437: A model of optical devices having potential for innovations in biomimicry . Scarab beetles in the genus Cyphochilus also utilize chitin to form extremely thin scales (five to fifteen micrometres thick) that diffusely reflect white light. These scales are networks of randomly ordered filaments of chitin with diameters on the scale of hundreds of nanometres , which serve to scatter light. The multiple scattering of light

657-479: A monosaccharide often coexists with a closed ring form where the aldehyde / ketone carbonyl group carbon (C=O) and hydroxyl group (–OH) react forming a hemiacetal with a new C–O–C bridge. Monosaccharides can be linked together into what are called polysaccharides (or oligosaccharides ) in a large variety of ways. Many carbohydrates contain one or more modified monosaccharide units that have had one or more groups replaced or removed. For example, deoxyribose ,

730-408: A reproducible form of biodegradable plastic. Chitin nanofibers are extracted from crustacean waste and mushrooms for possible development of products in tissue engineering , drug delivery and medicine. Chitin has been proposed for use in building structures, tools, and other solid objects from a composite material , combining chitin with Martian regolith . To build this, the biopolymers in

803-468: A symmetric molecule with no stereo centers. The assignment of D or L is made according to the orientation of the asymmetric carbon furthest from the carbonyl group: in a standard Fischer projection if the hydroxyl group is on the right the molecule is a D sugar, otherwise it is an L sugar. The "D-" and "L-" prefixes should not be confused with "d-" or "l-", which indicate the direction that the sugar rotates plane polarized light . This usage of "d-" and "l-"

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876-612: A wide range of applications in the biomedical industry. Chitin and chitosan have been explored as a vaccine adjuvant due to its ability to stimulate an immune response. Chitin and chitosan are under development as scaffolds in studies of how tissue grows and how wounds heal , and in efforts to invent better bandages , surgical thread , and materials for allotransplantation . Sutures made of chitin have been experimentally developed, but their lack of elasticity and problems making thread have prevented commercial success so far. Chitosan has been demonstrated and proposed to make

949-421: A wide variety of metabolic pathways across species: plants synthesize carbohydrates from carbon dioxide and water by photosynthesis storing the absorbed energy internally, often in the form of starch or lipids . Plant components are consumed by animals and fungi , and used as fuel for cellular respiration . Oxidation of one gram of carbohydrate yields approximately 16 kJ (4 kcal) of energy , while

1022-471: A wide variety of natural and processed foods. Starch is a polysaccharide and is abundant in cereals (wheat, maize, rice), potatoes, and processed food based on cereal flour , such as bread , pizza or pasta. Sugars appear in human diet mainly as table sugar (sucrose, extracted from sugarcane or sugar beets ), lactose (abundant in milk), glucose and fructose, both of which occur naturally in honey , many fruits , and some vegetables. Table sugar, milk, or honey

1095-691: Is O -β-D-galactopyranosyl-(1→4)-D-glucopyranose. Other notable disaccharides include maltose (two D-glucoses linked α-1,4) and cellobiose (two D-glucoses linked β-1,4). Disaccharides can be classified into two types: reducing and non-reducing disaccharides. If the functional group is present in bonding with another sugar unit, it is called a reducing disaccharide or biose. Oligosaccharides are saccharide polymers composed of three to ten units of monosaccharides, connected via glycosidic linkages , similar to disaccharides . They are usually linked to lipids or amino acids glycosic linkage with oxygen or nitrogen to form glygolipids and glycoproteins , though some, like

1168-555: Is a good inducer of plant defense mechanisms for controlling diseases . It has potential for use as a soil fertilizer or conditioner to improve fertility and plant resilience that may enhance crop yields. Chitin is used in many industrial processes. Examples of the potential uses of chemically modified chitin in food processing include the formation of edible films and as an additive to thicken and stabilize foods and food emulsions. Processes to size and strengthen paper employ chitin and chitosan. How chitin interacts with

1241-624: Is a measure of how quickly food glucose is absorbed, while glycemic load is a measure of the total absorbable glucose in foods. The insulin index is a similar, more recent classification method that ranks foods based on their effects on blood insulin levels, which are caused by glucose (or starch) and some amino acids in food. Low-carbohydrate diets may miss the health advantages – such as increased intake of dietary fiber – afforded by high-quality carbohydrates found in legumes and pulses , whole grains , fruits, and vegetables. A "meta-analysis, of moderate quality," included as adverse effects of

1314-483: Is a structural component of the cell wall of plants and many forms of algae. Ribose is a component of RNA . Deoxyribose is a component of DNA . Lyxose is a component of lyxoflavin found in the human heart. Ribulose and xylulose occur in the pentose phosphate pathway . Galactose , a component of milk sugar lactose , is found in galactolipids in plant cell membranes and in glycoproteins in many tissues . Mannose occurs in human metabolism, especially in

1387-428: Is an aldopentose (a five-carbon aldehyde), and fructose is a ketohexose (a six-carbon ketone). Each carbon atom bearing a hydroxyl group (-OH), with the exception of the first and last carbons, are asymmetric , making them stereo centers with two possible configurations each (R or S). Because of this asymmetry, a number of isomers may exist for any given monosaccharide formula. Using Le Bel-van't Hoff rule ,

1460-473: Is an example of a fungal pathogen that has such blocking proteins; it is a major pest in wheat crops. Chitin was probably present in the exoskeletons of Cambrian arthropods such as trilobites . The oldest preserved (intact) chitin samples thus far reported are dated to the Oligocene , about 25  million years ago , from specimens encased in amber where the chitin has not completely degraded. Chitin

1533-441: Is an important component of coenzymes (e.g., ATP , FAD and NAD ) and the backbone of the genetic molecule known as RNA . The related deoxyribose is a component of DNA. Saccharides and their derivatives include many other important biomolecules that play key roles in the immune system , fertilization , preventing pathogenesis , blood clotting , and development . Carbohydrates are central to nutrition and are found in

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1606-526: Is calculated in the USDA database and does not always correspond to the sum of the sugars, the starch, and the "dietary fiber". Carbohydrate metabolism is the series of biochemical processes responsible for the formation , breakdown and interconversion of carbohydrates in living organisms . The most important carbohydrate is glucose , a simple sugar ( monosaccharide ) that is metabolized by nearly all known organisms. Glucose and other carbohydrates are part of

1679-414: Is considered a fad diet by nutritionists. Nutritionist Jane Clark points to a lack of essential nutrients in this program, citing a deficiency of protein, vitamins, and minerals. As a result of these deficiencies, including far fewer calories than the recommended amount for health and optimum functioning, individuals on the diet may experience headaches and a variety of other symptoms in the short term and

1752-449: Is limited evidence to support routine use of low-carbohydrate dieting in managing type 1 diabetes . The American Diabetes Association recommends that people with diabetes should adopt a generally healthy diet, rather than a diet focused on carbohydrate or other macronutrients. An extreme form of low-carbohydrate diet – the ketogenic diet – is established as a medical diet for treating epilepsy . Through celebrity endorsement during

1825-474: Is most common in biochemistry , where it is a synonym of saccharide (from Ancient Greek σάκχαρον ( sákkharon )  'sugar' ), a group that includes sugars , starch , and cellulose . The saccharides are divided into four chemical groups: monosaccharides , disaccharides , oligosaccharides , and polysaccharides . Monosaccharides and disaccharides, the smallest (lower molecular weight ) carbohydrates, are commonly referred to as sugars. While

1898-421: Is no longer followed in carbohydrate chemistry. The aldehyde or ketone group of a straight-chain monosaccharide will react reversibly with a hydroxyl group on a different carbon atom to form a hemiacetal or hemiketal , forming a heterocyclic ring with an oxygen bridge between two carbon atoms. Rings with five and six atoms are called furanose and pyranose forms, respectively, and exist in equilibrium with

1971-454: Is not clear how low-carbohydrate dieting affects cardiovascular health , although two reviews showed that carbohydrate restriction may improve lipid markers of cardiovascular disease risk. Carbohydrate-restricted diets are no more effective than a conventional healthy diet in preventing the onset of type 2 diabetes , but for people with type 2 diabetes, they are a viable option for losing weight or helping with glycemic control . There

2044-496: Is often added to drinks and many prepared foods such as jam, biscuits and cakes. Cellulose , a polysaccharide found in the cell walls of all plants, is one of the main components of insoluble dietary fiber . Although it is not digestible by humans, cellulose and insoluble dietary fiber generally help maintain a healthy digestive system by facilitating bowel movements . Other polysaccharides contained in dietary fiber include resistant starch and inulin , which feed some bacteria in

2117-524: Is often modified, occurring largely as a component of composite materials , such as in sclerotin , a tanned proteinaceous matrix, which forms much of the exoskeleton of insects . Combined with calcium carbonate , as in the shells of crustaceans and molluscs , chitin produces a much stronger composite. This composite material is much harder and stiffer than pure chitin, and is tougher and less brittle than pure calcium carbonate . Another difference between pure and composite forms can be seen by comparing

2190-464: Is prepared, individual differences in metabolism, and the chemistry of the carbohydrate. Carbohydrates are sometimes divided into "available carbohydrates", which are absorbed in the small intestine and "unavailable carbohydrates", which pass to the large intestine , where they are subject to fermentation by the gastrointestinal microbiota . The USDA's Dietary Guidelines for Americans 2010 call for moderate- to high-carbohydrate consumption from

2263-463: Is required in the early steps of glycolysis to phosphorylate Glucose to Glucose 6-Phosphate ( G6P ) and Fructose 6-Phosphate ( F6P ) to Fructose 1,6-biphosphate ( FBP ), thereby pushing the reaction forward irreversibly. In some cases, as with humans, not all carbohydrate types are usable as the digestive and metabolic enzymes necessary are not present. Carbohydrate chemistry is a large and economically important branch of organic chemistry. Some of

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2336-458: Is sensed mostly in the lungs or gastrointestinal tract where it can activate the innate immune system through eosinophils or macrophages , as well as an adaptive immune response through T helper cells. Keratinocytes in skin can also react to chitin or chitin fragments. Plants also have receptors that can cause a response to chitin, namely chitin elicitor receptor kinase 1 and chitin elicitor-binding protein. The first chitin receptor

2409-438: Is the metabolic reaction which cells undergo to break down larger molecules, extracting energy. There are two major metabolic pathways of monosaccharide catabolism : glycolysis and the citric acid cycle . In glycolysis, oligo- and polysaccharides are cleaved first to smaller monosaccharides by enzymes called glycoside hydrolases . The monosaccharide units can then enter into monosaccharide catabolism. A 2 ATP investment

2482-450: Is the most abundant disaccharide, and the main form in which carbohydrates are transported in plants. It is composed of one D-glucose molecule and one D-fructose molecule. The systematic name for sucrose, O -α-D-glucopyranosyl-(1→2)-D-fructofuranoside, indicates four things: Lactose , a disaccharide composed of one D-galactose molecule and one D-glucose molecule, occurs naturally in mammalian milk. The systematic name for lactose

2555-565: Is thought to play a role in the unusual whiteness of the scales. In addition, some social wasps, such as Protopolybia chartergoides , orally secrete material containing predominantly chitin to reinforce the outer nest envelopes, composed of paper. Chitosan is produced commercially by deacetylation of chitin by treatment with sodium hydroxide . Chitosan has a wide range of biomedical applications including wound healing, drug delivery and tissue engineering. Due to its specific intermolecular hydrogen bonding network, dissolving chitin in water

2628-699: Is three or more. A typical monosaccharide has the structure H–(CHOH) x (C=O)–(CHOH) y –H, that is, an aldehyde or ketone with many hydroxyl groups added, usually one on each carbon atom that is not part of the aldehyde or ketone functional group . Examples of monosaccharides are glucose , fructose , and glyceraldehydes . However, some biological substances commonly called "monosaccharides" do not conform to this formula (e.g., uronic acids and deoxy-sugars such as fucose ) and there are many chemicals that do conform to this formula but are not considered to be monosaccharides (e.g., formaldehyde CH 2 O and inositol (CH 2 O) 6 ). The open-chain form of

2701-533: Is very difficult. Chitosan (with a degree of deacetylation of more than ~28%), on the other hand, can be dissolved in dilute acidic aqueous solutions below a pH of 6.0 such as acetic, formic and lactic acids. Chitosan with a degree of deacetylation greater than ~49% is soluble in water Humans and other mammals have chitinase and chitinase-like proteins that can degrade chitin; they also possess several immune receptors that can recognize chitin and its degradation products, initiating an immune response . Chitin

2774-535: The glycosylation of certain proteins. Fructose , or fruit sugar, is found in many plants and humans, it is metabolized in the liver, absorbed directly into the intestines during digestion , and found in semen . Trehalose , a major sugar of insects, is rapidly hydrolyzed into two glucose molecules to support continuous flight. Two joined monosaccharides are called a disaccharide , the simplest kind of polysaccharide. Examples include sucrose and lactose . They are composed of two monosaccharide units bound together by

2847-414: The immune system of plants and animals has been an active area of research, including the identity of key receptors with which chitin interacts, whether the size of chitin particles is relevant to the kind of immune response triggered, and mechanisms by which immune systems respond. Chitin is deacetylated chemically or enzymatically to produce chitosan , a highly biocompatible polymer which has found

2920-1078: The lac operon will express enzymes for the digestion of lactose when it is present, but if both lactose and glucose are present the lac operon is repressed, resulting in the glucose being used first (see: Diauxie ). Polysaccharides are also common sources of energy. Many organisms can easily break down starches into glucose; most organisms, however, cannot metabolize cellulose or other polysaccharides like chitin and arabinoxylans . These carbohydrate types can be metabolized by some bacteria and protists. Ruminants and termites , for example, use microorganisms to process cellulose. Even though these complex carbohydrates are not very digestible, they represent an important dietary element for humans, called dietary fiber . Fiber enhances digestion, among other benefits. The Institute of Medicine recommends that American and Canadian adults get between 45 and 65% of dietary energy from whole-grain carbohydrates. The Food and Agriculture Organization and World Health Organization jointly recommend that national dietary guidelines set

2993-486: The microbiota of the large intestine , and are metabolized by these bacteria to yield short-chain fatty acids . In scientific literature , the term "carbohydrate" has many synonyms, like "sugar" (in the broad sense), "saccharide", "ose", "glucide", "hydrate of carbon" or " polyhydroxy compounds with aldehyde or ketone ". Some of these terms, especially "carbohydrate" and "sugar", are also used with other meanings. In food science and in many informal contexts,

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3066-769: The raffinose series and the fructooligosaccharides , do not. They have roles in cell recognition and cell adhesion . Carbohydrate consumed in food yields 3.87 kilocalories of energy per gram for simple sugars, and 3.57 to 4.12 kilocalories per gram for complex carbohydrate in most other foods. Relatively high levels of carbohydrate are associated with processed foods or refined foods made from plants, including sweets, cookies and candy, table sugar, honey, soft drinks, breads and crackers, jams and fruit products, pastas and breakfast cereals. Lower amounts of digestible carbohydrate are usually associated with unrefined foods as these foods have more fiber, including beans, tubers, rice, and unrefined fruit . Animal-based foods generally have

3139-687: The scientific nomenclature of carbohydrates is complex, the names of the monosaccharides and disaccharides very often end in the suffix -ose , which was originally taken from the word glucose (from Ancient Greek γλεῦκος ( gleûkos )  'wine, must '), and is used for almost all sugars (e.g., fructose (fruit sugar), sucrose ( cane or beet sugar), ribose , lactose (milk sugar)). Carbohydrates perform numerous roles in living organisms. Polysaccharides serve as an energy store (e.g., starch and glycogen ) and as structural components (e.g., cellulose in plants and chitin in arthropods and fungi). The 5-carbon monosaccharide ribose

3212-445: The -OH substituent on the anomeric carbon rests on the opposite side ( trans ) of the ring from the CH 2 OH side branch. The alternative form, in which the CH 2 OH substituent and the anomeric hydroxyl are on the same side (cis) of the plane of the ring, is called the β anomer . Monosaccharides are the major fuel source for metabolism , being used both as an energy source ( glucose being

3285-403: The H has covalent bonds with O (for example with CH 2 O , H has a covalent bond with C but not with O). However, not all carbohydrates conform to this precise stoichiometric definition (e.g., uronic acids , deoxy-sugars such as fucose ), nor are all chemicals that do conform to this definition automatically classified as carbohydrates (e.g., formaldehyde and acetic acid ). The term

3358-489: The Master Cleanse diet when American singer Beyoncé promoted it on The Oprah Winfrey Show in 2006. Carbohydrate A carbohydrate ( / ˌ k ɑːr b oʊ ˈ h aɪ d r eɪ t / ) is a biomolecule consisting of carbon (C), hydrogen (H) and oxygen (O) atoms, usually with a hydrogen–oxygen atom ratio of 2:1 (as in water) and thus with the empirical formula C m (H 2 O) n (where m may or may not be different from n ), which does not mean

3431-401: The aldohexose D-glucose, for example, has the formula (C·H 2 O) 6 , of which four of its six carbons atoms are stereogenic, making D-glucose one of 2 =16 possible stereoisomers . In the case of glyceraldehydes , an aldotriose, there is one pair of possible stereoisomers, which are enantiomers and epimers . 1, 3-dihydroxyacetone , the ketose corresponding to the aldose glyceraldehydes, is

3504-419: The amount of fat vs carbohydrate in the diet." In the long term, effective weight loss or maintenance depends on calorie restriction , not the ratio of macronutrients in a diet. The reasoning of diet advocates that carbohydrates cause undue fat accumulation by increasing blood insulin levels, and that low-carbohydrate diets have a "metabolic advantage", is not supported by clinical evidence . Further, it

3577-479: The biosphere. It is a primary component of cell walls in fungi (especially filamentous and mushroom-forming fungi), the exoskeletons of arthropods such as crustaceans and insects, the radulae , cephalopod beaks and gladii of molluscs and in some nematodes and diatoms. It is also synthesised by at least some fish and lissamphibians . Commercially, chitin is extracted from the shells of crabs, shrimps, shellfish and lobsters, which are major by-products of

3650-433: The carbonyl group is an aldehyde , the monosaccharide is an aldose ; if the carbonyl group is a ketone , the monosaccharide is a ketose . Monosaccharides with three carbon atoms are called trioses , those with four are called tetroses , five are called pentoses , six are hexoses , and so on. These two systems of classification are often combined. For example, glucose is an aldohexose (a six-carbon aldehyde), ribose

3723-401: The diet halitosis , headache and constipation . Carbohydrate-restricted diets can be as effective as low-fat diets in helping achieve weight loss over the short term when overall calorie intake is reduced. An Endocrine Society scientific statement said that "when calorie intake is held constant [...] body-fat accumulation does not appear to be affected by even very pronounced changes in

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3796-409: The diet is potentially harmful over the long term. While the Master Cleanse diet can result in short-term weight loss, unless lasting changes are incorporated into one's diet after the regimen, the weight lost during the fast will be regained once the diet is stopped. Dietician Keri Glassman has said those following the diet are "guaranteed" to gain weight after stopping. There was popular interest in

3869-413: The early 21st century, it became a fad diet as a means of weight loss, but with risks of undesirable side effects , such as low energy levels and increased hunger, insomnia , nausea, and gastrointestinal discomfort. The British Dietetic Association named it one of the "top 5 worst celeb diets to avoid in 2018". Most dietary carbohydrates contain glucose, either as their only building block (as in

3942-449: The flexible body wall of a caterpillar (mainly chitin) to the stiff, light elytron of a beetle (containing a large proportion of sclerotin ). In butterfly wing scales, chitin is organized into stacks of gyroids constructed of chitin photonic crystals that produce various iridescent colors serving phenotypic signaling and communication for mating and foraging. The elaborate chitin gyroid construction in butterfly wings creates

4015-446: The linkages between glucose units forming cellulose ). Therefore, chitin may be described as cellulose with one hydroxyl group on each monomer replaced with an acetyl amine group. This allows for increased hydrogen bonding between adjacent polymers , giving the chitin-polymer matrix increased strength. In its pure, unmodified form, chitin is translucent, pliable, resilient, and quite tough. In most arthropods , however, it

4088-409: The lowest carbohydrate levels, although milk does contain a high proportion of lactose . Organisms typically cannot metabolize all types of carbohydrate to yield energy. Glucose is a nearly universal and accessible source of energy. Many organisms also have the ability to metabolize other monosaccharides and disaccharides but glucose is often metabolized first. In Escherichia coli , for example,

4161-476: The main organic reactions that involve carbohydrates are: Carbohydrate synthesis is a sub-field of organic chemistry concerned specifically with the generation of natural and unnatural carbohydrate structures. This can include the synthesis of monosaccharide residues or structures containing more than one monosaccharide, known as oligosaccharides . Selective formation of glycosidic linkages and selective reactions of hydroxyl groups are very important, and

4234-459: The most important in nature as it is the product of photosynthesis in plants) and in biosynthesis . When monosaccharides are not immediately needed, they are often converted to more space-efficient (i.e., less water-soluble) forms, often polysaccharides . In many animals, including humans, this storage form is glycogen , especially in liver and muscle cells. In plants, starch is used for the same purpose. The most abundant carbohydrate, cellulose ,

4307-547: The oxidation of one gram of lipids yields about 38 kJ (9 kcal). The human body stores between 300 and 500 g of carbohydrates depending on body weight, with the skeletal muscle contributing to a large portion of the storage. Energy obtained from metabolism (e.g., oxidation of glucose) is usually stored temporarily within cells in the form of ATP . Organisms capable of anaerobic and aerobic respiration metabolize glucose and oxygen (aerobic) to release energy, with carbon dioxide and water as byproducts. Catabolism

4380-636: The polysaccharides starch and glycogen), or together with another monosaccharide (as in the hetero-polysaccharides sucrose and lactose). Unbound glucose is one of the main ingredients of honey. Glucose is extremely abundant and has been isolated from a variety of natural sources across the world, including male cones of the coniferous tree Wollemia nobilis in Rome, the roots of Ilex asprella plants in China, and straws from rice in California. ^A The carbohydrate value

4453-439: The position of the hydroxyl group (red or green) on the anomeric carbon relative to the CH 2 OH group bound to carbon 5: they either have identical absolute configurations (R,R or S,S) (α), or opposite absolute configurations (R,S or S,R) (β). Monosaccharides are classified according to three different characteristics: the placement of its carbonyl group, the number of carbon atoms it contains, and its chiral handedness. If

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4526-555: The seafood industry. The structure of chitin is comparable to cellulose, forming crystalline nanofibrils or whiskers. It is functionally comparable to the protein keratin . Chitin has proved useful for several medicinal, industrial and biotechnological purposes. The English word "chitin" comes from the French word chitine , which was derived in 1821 from the Greek word χιτών ( khitōn ) meaning covering. A similar word, " chiton ", refers to

4599-406: The simple vs. complex chemical distinction has little value for determining the nutritional quality of carbohydrates. Some simple carbohydrates (e.g., fructose ) raise blood glucose rapidly, while some complex carbohydrates (starches), raise blood sugar slowly. The speed of digestion is determined by a variety of factors including which other nutrients are consumed with the carbohydrate, how the food

4672-533: The simplest carbohydrates in that they cannot be hydrolyzed to smaller carbohydrates. They are aldehydes or ketones with two or more hydroxyl groups. The general chemical formula of an unmodified monosaccharide is (C•H 2 O) n , literally a "carbon hydrate". Monosaccharides are important fuel molecules as well as building blocks for nucleic acids. The smallest monosaccharides, for which n=3, are dihydroxyacetone and D- and L-glyceraldehydes. [REDACTED] [REDACTED] The α and β anomers of glucose. Note

4745-401: The straight-chain form. During the conversion from straight-chain form to the cyclic form, the carbon atom containing the carbonyl oxygen, called the anomeric carbon , becomes a stereogenic center with two possible configurations: The oxygen atom may take a position either above or below the plane of the ring. The resulting possible pair of stereoisomers is called anomers . In the α anomer ,

4818-533: The strict sense, " sugar " is applied for sweet, soluble carbohydrates, many of which are used in human food. The history of the discovery regarding carbohydrates dates back around 10,000 years ago in Papua New Guinea during the cultivation of sugarcane during the Neolithic agricultural revolution. The term "carbohydrate" was first proposed by German chemist Carl Schmidt (chemist) in 1844. In 1856, glycogen ,

4891-438: The term "carbohydrate" (or "carbohydrate by difference") is used for everything other than water, protein, fat, ash, and ethanol. This includes chemical compounds such as acetic or lactic acid , which are not normally considered carbohydrates. It also includes dietary fiber which is a carbohydrate but which does not contribute food energy in humans, even though it is often included in the calculation of total food energy. In

4964-496: The term "carbohydrate" often means any food that is particularly rich in the complex carbohydrate starch (such as cereals, bread and pasta) or simple carbohydrates, such as sugar (found in candy, jams , and desserts). This informality is sometimes confusing since it confounds chemical structure and digestibility in humans. Often in lists of nutritional information , such as the USDA National Nutrient Database ,

5037-456: The term complex carbohydrate to refer to any sort of digestible saccharide present in a whole food, where fiber, vitamins and minerals are also found (as opposed to processed carbohydrates, which provide energy but few other nutrients). The standard usage, however, is to classify carbohydrates chemically: simple if they are sugars ( monosaccharides and disaccharides ) and complex if they are polysaccharides (or oligosaccharides ). In any case,

5110-714: The term is generally understood in the biochemistry sense, which excludes compounds with only one or two carbons and includes many biological carbohydrates which deviate from this formula. For example, while the above representative formulas would seem to capture the commonly known carbohydrates, ubiquitous and abundant carbohydrates often deviate from this. For example, carbohydrates often display chemical groups such as: N -acetyl (e.g., chitin ), sulfate (e.g., glycosaminoglycans ), carboxylic acid and deoxy modifications (e.g., fucose and sialic acid ). Natural saccharides are generally built of simple carbohydrates called monosaccharides with general formula (CH 2 O) n where n

5183-560: The usage of protecting groups is extensive. Common reactions for glycosidic bond formation are as follows: While some common protection methods are as below: Chitin Chitin ( C 8 H 13 O 5 N ) n ( / ˈ k aɪ t ɪ n / KY -tin ) is a long-chain polymer of N -acetylglucosamine , an amide derivative of glucose . Chitin is the second most abundant polysaccharide in nature (behind only cellulose ); an estimated 1 billion tons of chitin are produced each year in

5256-438: Was cloned in 2006. When the receptors are activated by chitin, genes related to plant defense are expressed, and jasmonate hormones are activated, which in turn activate systemic defenses. Commensal fungi have ways to interact with the host immune response that, as of 2016 , were not well understood. Some pathogens produce chitin-binding proteins that mask the chitin they shed from these receptors. Zymoseptoria tritici

5329-545: Was first used in the U.S. Senate Select Committee on Nutrition and Human Needs publication Dietary Goals for the United States (1977) where it was intended to distinguish sugars from other carbohydrates (which were perceived to be nutritionally superior). However, the report put "fruit, vegetables and whole-grains" in the complex carbohydrate column, despite the fact that these may contain sugars as well as polysaccharides. This confusion persists as today some nutritionists use

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