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85-576: 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

170-401: 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,

255-413: 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

340-517: 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

425-399: 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,

510-467: 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

595-479: 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 ,

680-464: A reaction catalysed by UTP—glucose-1-phosphate uridylyltransferase . Glycogen is synthesized from monomers of UDP-glucose initially by the protein glycogenin , which has two tyrosine anchors for the reducing end of glycogen, since glycogenin is a homodimer. After about eight glucose molecules have been added to a tyrosine residue, the enzyme glycogen synthase progressively lengthens the glycogen chain using UDP-glucose, adding α(1→4)-bonded glucose to

765-435: A solution to storing glucose in the cell without disrupting osmotic pressure. As a meal containing carbohydrates or protein is eaten and digested , blood glucose levels rise, and the pancreas secretes insulin . Blood glucose from the portal vein enters liver cells ( hepatocytes ). Insulin acts on the hepatocytes to stimulate the action of several enzymes , including glycogen synthase . Glucose molecules are added to

850-516: A sudden need for glucose, but one that is less compact than the energy reserves of triglycerides ( lipids ). As such it is also found as storage reserve in many parasitic protozoa. Glycogen is a branched biopolymer consisting of linear chains of glucose residues with an average chain length of approximately 8–12 glucose units and 2,000-60,000 residues per one molecule of glycogen. Like amylopectin, glucose units are linked together linearly by α(1→4) glycosidic bonds from one glucose to

935-468: 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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1020-421: 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

1105-471: 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

1190-691: 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

1275-624: 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

1360-483: 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

1445-428: 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 ,

1530-481: Is an analogue of starch , a glucose polymer that functions as energy storage in plants . It has a structure similar to amylopectin (a component of starch), but is more extensively branched and compact than starch. Both are white powders in their dry state. Glycogen is found in the form of granules in the cytosol /cytoplasm in many cell types, and plays an important role in the glucose cycle . Glycogen forms an energy reserve that can be quickly mobilized to meet

1615-441: 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

1700-530: 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

1785-420: Is cleaved from the nonreducing ends of the chain by the enzyme glycogen phosphorylase to produce monomers of glucose-1-phosphate: In vivo, phosphorolysis proceeds in the direction of glycogen breakdown because the ratio of phosphate and glucose-1-phosphate is usually greater than 100. Glucose-1-phosphate is then converted to glucose 6 phosphate (G6P) by phosphoglucomutase . A special debranching enzyme

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1870-414: 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

1955-560: Is formed by the self-glucosylation of the glycogenin, forming a short primer chain. From the C-chain grows out B-chains, and from B-chains branch out B- and A-chains. The B-chains have on average 2 branch points, while the A-chains are terminal, thus unbranched. On average, each chain has length 12, tightly constrained to be between 11 and 15. All A-chains reach the spherical surface of the glycogen. Glycogen in muscle, liver, and fat cells

2040-686: Is known as the sliding filament theory . Skeletal muscle relies predominantly on glycogenolysis for the first few minutes as it transitions from rest to activity, as well as throughout high-intensity aerobic activity and all anaerobic activity. During anaerobic activity, such as weightlifting and isometric exercise , the phosphagen system (ATP-PCr) and muscle glycogen are the only substrates used as they do not require oxygen nor blood flow. Different bioenergetic systems produce ATP at different speeds, with ATP produced from muscle glycogen being much faster than fatty acid oxidation. The level of exercise intensity determines how much of which substrate (fuel)

2125-449: 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

2210-474: 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

2295-540: Is needed to remove the α(1→6) branches in branched glycogen and reshape the chain into a linear polymer. The G6P monomers produced have three possible fates: The most common disease in which glycogen metabolism becomes abnormal is diabetes , in which, because of abnormal amounts of insulin, liver glycogen can be abnormally accumulated or depleted. Restoration of normal glucose metabolism usually normalizes glycogen metabolism, as well. In hypoglycemia caused by excessive insulin, liver glycogen levels are high, but

2380-421: 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

2465-454: 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

2550-430: Is not fractal in nature. This has been subsequently verified by others who have performed Monte Carlo simulations of glycogen particle growth, and shown that the molecular density reaches a maximum near the centre of the nanoparticle structure, not at the periphery (contradicting a fractal structure that would have greater density at the periphery). Glycogen was discovered by Claude Bernard . His experiments showed that

2635-496: 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

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2720-464: 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

2805-463: 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

2890-412: Is required to pass glucose into the blood, the glycogen they store is available solely for internal use and is not shared with other cells. This is in contrast to liver cells, which, on demand, readily do break down their stored glycogen into glucose and send it through the blood stream as fuel for other organs. Skeletal muscle needs ATP (provides energy) for muscle contraction and relaxation, in what

2975-528: Is secreted in increasing amounts and stimulates both glycogenolysis (the breakdown of glycogen) and gluconeogenesis (the production of glucose from other sources). Muscle glycogen appears to function as a reserve of quickly available phosphorylated glucose, in the form of glucose-1-phosphate , for muscle cells. Glycogen contained within skeletal muscle cells are primarily in the form of β particles. Other cells that contain small amounts use it locally as well. As muscle cells lack glucose-6-phosphatase , which

3060-431: Is stored in a hydrated form, composed of three or four parts of water per part of glycogen associated with 0.45  millimoles (18 mg) of potassium per gram of glycogen. Glucose is an osmotic molecule, and can have profound effects on osmotic pressure in high concentrations possibly leading to cell damage or death if stored in the cell without being modified. Glycogen is a non-osmotic molecule, so it can be used as

3145-438: 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

3230-450: 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

3315-421: Is the primary enzyme of glycogen breakdown. For the next 8–12 hours, glucose derived from liver glycogen is the primary source of blood glucose used by the rest of the body for fuel. Glucagon , another hormone produced by the pancreas, in many respects serves as a countersignal to insulin. In response to insulin levels being below normal (when blood levels of glucose begin to fall below the normal range), glucagon

3400-699: 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

3485-414: Is used for ATP synthesis also. Muscle glycogen can supply a much higher rate of substrate for ATP synthesis than blood glucose. During maximum intensity exercise, muscle glycogen can supply 40 mmol glucose/kg wet weight/minute, whereas blood glucose can supply 4 - 5 mmol. Due to its high supply rate and quick ATP synthesis, during high-intensity aerobic activity (such as brisk walking, jogging, or running),

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3570-412: The blood of humans at all times; in fasting individuals, blood glucose is maintained constant at this level at the expense of glycogen stores, primarily from the liver (glycogen in skeletal muscle is mainly used as an immediate source of energy for that muscle rather than being used to maintain physiological blood glucose levels). Glycogen stores in skeletal muscle serve as a form of energy storage for

3655-536: The brain . The uterus also stores glycogen during pregnancy to nourish the embryo. The amount of glycogen stored in the body mostly depends on oxidative type 1 fibres , physical training, basal metabolic rate , and eating habits. Different levels of resting muscle glycogen are reached by changing the number of glycogen particles, rather than increasing the size of existing particles though most glycogen particles at rest are smaller than their theoretical maximum. Approximately 4 grams of glucose are present in

3740-535: 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

3825-1078: 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

3910-486: 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,

3995-769: 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

4080-687: 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

4165-424: The triglyceride stores in adipose tissue (i.e., body fat) being for long-term storage. Protein, broken down into amino acids, is seldom used as a main energy source except during starvation and glycolytic crisis (see bioenergetic systems ) . In humans , glycogen is made and stored primarily in the cells of the liver and skeletal muscle . In the liver, glycogen can make up 5–6% of the organ's fresh weight:

4250-448: 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

4335-403: 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

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4420-489: 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

4505-401: 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

4590-419: 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

4675-431: The athlete's glycogen stores are depleted after long periods of exertion without sufficient carbohydrate consumption. This phenomenon is referred to as " hitting the wall " in running and "bonking" in cycling. Glycogen depletion can be forestalled in three possible ways: When athletes ingest both carbohydrate and caffeine following exhaustive exercise, their glycogen stores tend to be replenished more rapidly; however,

4760-433: 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

4845-419: The chains of glycogen as long as both insulin and glucose remain plentiful. In this postprandial or "fed" state, the liver takes in more glucose from the blood than it releases. After a meal has been digested and glucose levels begin to fall, insulin secretion is reduced, and glycogen synthesis stops. When it is needed for energy , glycogen is broken down and converted again to glucose. Glycogen phosphorylase

4930-401: 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

5015-409: 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

5100-413: 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

5185-543: The high insulin levels prevent the glycogenolysis necessary to maintain normal blood sugar levels. Glucagon is a common treatment for this type of hypoglycemia. Various inborn errors of carbohydrate metabolism are caused by deficiencies of enzymes or transport proteins necessary for glycogen synthesis or breakdown. These are collectively referred to as glycogen storage diseases . Long-distance athletes, such as marathon runners, cross-country skiers , and cyclists , often experience glycogen depletion, where almost all of

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5270-464: The higher the exercise intensity, the more the muscle cell produces ATP from muscle glycogen. This reliance on muscle glycogen is not only to provide the muscle with enough ATP during high-intensity exercise, but also to maintain blood glucose homeostasis (that is, to not become hypoglycaemic by the muscles needing to extract far more glucose from the blood than the liver can provide). A deficit of muscle glycogen leads to muscle fatigue known as "hitting

5355-427: The liver contained a substance that could give rise to reducing sugar by the action of a "ferment" in the liver. By 1857, he described the isolation of a substance he called " la matière glycogène ", or "sugar-forming substance". Soon after the discovery of glycogen in the liver, M.A. Sanson found that muscular tissue also contains glycogen. The empirical formula for glycogen of ( C 6 H 10 O 5 ) n

5440-441: The liver of an adult, weighing 1.5 kg, can store roughly 100–120 grams of glycogen. In skeletal muscle, glycogen is found in a low concentration (1–2% of the muscle mass): the skeletal muscle of an adult weighing 70 kg stores roughly 400 grams of glycogen. Small amounts of glycogen are also found in other tissues and cells, including the kidneys , red blood cells , white blood cells , and glial cells in

5525-409: 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,

5610-476: 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

5695-459: 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 ,

5780-422: The muscle itself; however, the breakdown of muscle glycogen impedes muscle glucose uptake from the blood, thereby increasing the amount of blood glucose available for use in other tissues. Liver glycogen stores serve as a store of glucose for use throughout the body, particularly the central nervous system . The human brain consumes approximately 60% of blood glucose in fasted, sedentary individuals. Glycogen

5865-414: The next. Branches are linked to the chains from which they are branching off by α(1→6) glycosidic bonds between the first glucose of the new branch and a glucose on the stem chain. Each glycogen is essentially a ball of glucose trees, with around 12 layers, centered on a glycogenin protein, with three kinds of glucose chains: A, B, and C. There is only one C-chain, attached to the glycogenin. This C-chain

5950-513: The nonreducing end of the glycogen chain. The glycogen branching enzyme catalyzes the transfer of a terminal fragment of six or seven glucose residues from a nonreducing end to the C-6 ;hydroxyl group of a glucose residue deeper into the interior of the glycogen molecule. The branching enzyme can act upon only a branch having at least 11 residues, and the enzyme may transfer to the same glucose chain or adjacent glucose chains. Glycogen

6035-547: 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

6120-650: 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

6205-439: 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

6290-406: 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

6375-533: 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

6460-401: 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 ,

6545-546: 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 ,

6630-438: 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

6715-509: 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 ,

6800-456: 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,

6885-714: 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

6970-545: The usage of protecting groups is extensive. Common reactions for glycosidic bond formation are as follows: While some common protection methods are as below: Glycogen Glycogen is a multibranched polysaccharide of glucose that serves as a form of energy storage in animals , fungi , and bacteria. It is the main storage form of glucose in the human body. Glycogen functions as one of three regularly used forms of energy reserves, creatine phosphate being for very short-term, glycogen being for short-term and

7055-451: The wall" or "the bonk" (see below under glycogen depletion) . In 1999, Meléndez et al claimed that the structure of glycogen is optimal under a particular metabolic constraint model, where the structure was suggested to be "fractal" in nature. However, research by Besford et al used small angle X-ray scattering experiments accompanied by branching theory models to show that glycogen is a randomly hyperbranched polymer nanoparticle. Glycogen

7140-436: Was established by August Kekulé in 1858. Sanson, M. A. "Note sur la formation physiologique du sucre dans l’economie animale." Comptes rendus des seances de l’Academie des Sciences 44 (1857): 1323-5. Glycogen synthesis is, unlike its breakdown, endergonic —it requires the input of energy. Energy for glycogen synthesis comes from uridine triphosphate (UTP), which reacts with glucose-1-phosphate , forming UDP-glucose , in

7225-552: 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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