Carbohydrate: Difference between revisions

Latest revision as of 13:16, 4 November 2025

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Lactose is a disaccharide found in animal milk. It consists of a molecule of D-galactose and a molecule of D-glucose bonded by beta-1-4 glycosidic linkage.

A carbohydrate (Template:IPAc-en) is a sugar (saccharide) or a sugar derivative.^[1] For the simplest carbohydrates, the carbon-to-hydrogen-to-oxygen atomic ratio is 1:2:1, i.e. they are often represented by the empirical formula Template:Chem2. Together with amino acids, fats, and nucleic acids, the carbohydrates are one of the major families of biomolecules.^[2]

Carbohydrates perform numerous roles in living organisms.^[3] 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 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 play key roles in the immune system, fertilization, preventing pathogenesis, blood clotting, and development.^[4]

Carbohydrates are central to nutrition and are found in 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 is often added to drinks and many prepared foods such as jam, biscuits and cakes.

Terminology

The term "carbohydrate" has many synonyms and the definition can depend on context. Terms associated with carbohydrate include "sugar", "saccharide", "glucan",^[5] and "glucide".^[6] In food science the term "carbohydrate" often means any food that is rich in starch (such as cereals, bread and pasta) or simple carbohydrates, or fairly simple sugars such as sucrose (found in candy, jams, and desserts). Carbohydrates can also refer to dietary fiber, like cellulose.^[7]^[8]

Saccharides

The starting point for discussion of carbohydrates are the saccharides. Monosaccharides are the simplest carbohydrates in that they cannot be hydrolyzed to smaller carbohydrates. Monosaccharides usually have the formula C_m (H₂O)_n. Disaccharides (e.g. sucrose) are common as are polysaccharides/oligosaccharides (e.g., starch, cellulose). Saccharides are polyhydroxy aldehydes, ketones as well as derived polymers having linkages of the acetal type. They may be classified according to their degree of polymerization. Many polyols are also classified as carbohydrates. In many carbohydrates the OH groups are appended to or replaced by N-acetyl (e.g., chitin), sulfate (e.g., glycosaminoglycans), carboxylic acid and deoxy modifications (e.g., fucose and sialic acid).^[6]

The major dietary carbohydrates
Class (degree of polymerization)	Subgroup	Components
Sugars (1–2)	Monosaccharides	Glucose, galactose, fructose, xylose
	Disaccharides	Sucrose, lactose, maltose, isomaltulose, trehalose
	Polyols	Sorbitol, mannitol
Oligosaccharides (3–9)	Malto-oligosaccharides	Maltodextrins
Oligosaccharides (3–9)	Other oligosaccharides	Raffinose, stachyose, fructo-oligosaccharides
Polysaccharides (>9)	Starch	Amylose, amylopectin, modified starches
Polysaccharides (>9)	Non-starch polysaccharides	Glycogen, Cellulose, Hemicellulose, Pectins, Hydrocolloids

Complex carbohydrates

File:Heparin General Structure V.1.svg

Heparin, a carbohydrate, is a blood anticoagulant.^[9]

Script error: No such module "Labelled list hatnote". Sugars may be linked to other types of biological molecules to form glycoconjugates. The enzymatic process of glycosylation creates sugars/saccharides linked to themselves and to other molecules by the glycosidic bond, thereby producing glycans. Glycoproteins, proteoglycans and glycolipids are the most abundant glycoconjugates found in mammalian cells. They are found predominantly on the outer cell membrane and in secreted fluids. Glycoconjugates have been shown to be important in cell-cell interactions due to the presence on the cell surface of various glycan binding receptors in addition to the glycoconjugates themselves.^[10]^[11] In addition to their function in protein folding and cellular attachment, the N-linked glycans of a protein can modulate the protein's function, in some cases acting as an on-off switch.^[12]

History

File:Baeyer-Volhard LMU 1877.jpg

Emil Fischer, who elucidated the structure of glucose, with colleagues and student in their laboratory of Ludwig Maximilian University of Munich in 1877.

The history of carbohydrates, to some extent, is the history of sugar cane, which was first grown in New Guinea. The mass cultivation occurred in India where techniques were developed for the isolatoin of crystalline sugar.^[13] Cane sugar and its cultivation reached Europe around the 13th Century and then expanded to the New World, where industrialization occurred.

The chemistry and biochemistry of carbohydrates can be traced to 1811. On that year Constantin Kirchhoff discovered that grape sugar (glucose) forms when starch is boiled with acid. The starch industry started the following year. Henri Braconnot discovered in 1819 that sugar is formed through the action of sulfuric acid on cellulose. William Prout, after chemical analyses of sugar and starch by Joseph Louis Gay-Lussac and Thénard, gave this group of substances the group name "saccharine." The term "carbohydrate" was first proposed by German chemist Carl Schmidt (chemist) in 1844. In 1856, glycogen, a form of carbohydrate storage in animal livers, was discovered by French physiologist Claude Bernard.^[14] Emil Fischer received the 1902 Nobel Prize in Chemistry for his work on sugars and purines. For the discovery of glucose metabolism, Otto Meyerhof received the 1922 Nobel Prize in Physiology or Medicine. Hans von Euler-Chelpin, together with Arthur Harden, received the 1929 Nobel Prize in Chemistry "for their research on sugar fermentation and the role of enzymes in this process." In 1947, both Bernardo Houssay for his discovery of the role of the pituitary gland in carbohydrate metabolism and Carl and Gerty Cori for their discovery of the conversion of glycogen received the Nobel Prize in Physiology or Medicine. For the discovery of sugar nucleotides in carbohydrate biosynthesis, Luis Leloir received the 1970 Nobel Prize in Chemistry.

The term glycobiology^[15] was coined in 1988 by Raymond Dwek to recognize the coming together of the traditional disciplines of carbohydrate chemistry and biochemistry.^[16] This coming together was as a result of a much greater understanding of the cellular and molecular biology of glycans. "Glycoscience" is a field that explores the structures and functions of glycans.^[17]

Nutrition

File:GrainProducts.jpg

Grain products: rich sources of carbohydrates

Carbohydrate consumed in food yields 3.87 kilocalories of energy per gram for simple sugars,^[18] and 3.57 to 4.12 kilocalories per gram for complex carbohydrate in most other foods.^[19] 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. Refined carbohydrates from processed foods such as white bread or rice, soft drinks, and desserts are readily digestible, and many are known to have a high glycemic index, which reflects a rapid assimilation of glucose. By contrast, the digestion of whole, unprocessed, fiber-rich foods such as beans, peas, and whole grains produces a slower and steadier release of glucose and energy into the body.^[20] Animal-based foods generally have 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, 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 such as chitin and arabinoxylans. These carbohydrate types can be metabolized by some bacteria and protists. Ruminants and termites, for example, use microorganisms to process cellulose, fermenting it to caloric short-chain fatty acids. Even though humans lack the enzymes to digest fiber, dietary fiber represents an important dietary element for humans. Fibers promote healthy digestion, help regulate postprandial glucose and insulin levels, reduce cholesterol levels, and promote satiety.^[21]

The Institute of Medicine recommends that American and Canadian adults get between 45 and 65% of dietary energy from whole-grain carbohydrates.^[22] The Food and Agriculture Organization and World Health Organization jointly recommend that national dietary guidelines set a goal of 55–75% of total energy from carbohydrates, but only 10% directly from sugars (their term for simple carbohydrates).^[23] A 2017 Cochrane Systematic Review concluded that there was insufficient evidence to support the claim that whole grain diets can affect cardiovascular disease.^[24]

Carbohydrates are 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.^[7] Other polysaccharides contained in dietary fiber include resistant starch and inulin, which feed some bacteria in the microbiota of the large intestine, and are metabolized by these bacteria to yield short-chain fatty acids.^[7]^[25]^[26]

Classification

The term complex carbohydrate 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).^[27] 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. 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).^[7]^[28] 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.^[7]

Glycemic index

The glycemic index (GI) and glycemic load concepts characterize the potential for carbohydrates in food to raise blood glucose compared to a reference food (generally pure glucose).^[29] Expressed numerically as GI, carbohydrate-containing foods can be grouped as high-GI (score more than 70), moderate-GI (56–69), or low-GI (less than 55) relative to pure glucose (GI=100).^[29] Consumption of carbohydrate-rich, high-GI foods causes an abrupt increase in blood glucose concentration that declines rapidly following the meal, whereas low-GI foods with lower carbohydrate content produces a lower blood glucose concentration that returns gradually after the meal.^[29]

Glycemic load is a measure relating the quality of carbohydrates in a food (low- vs. high-carbohydrate content – the GI) by the amount of carbohydrates in a single serving of that food.^[29]

Health effects of dietary carbohydrate restriction

Script error: No such module "Labelled list hatnote". Low-carbohydrate diets may miss the health advantages – such as increased intake of dietary fiber and phytochemicals – afforded by high-quality plant foods such as legumes and pulses, whole grains, fruits, and vegetables.^[30]^[31] A "meta-analysis, of moderate quality," included as adverse effects of the diet halitosis, headache and constipation.^[32]Template:Better source needed

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.^[33] 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 the amount of fat vs carbohydrate in the diet."^[33] In the long term, low-carbohydrate diets do not appear to confer a "metabolic advantage," and effective weight loss or maintenance depends on the level of calorie restriction,^[33] not the ratio of macronutrients in a diet.^[34] The reasoning of diet advocates that carbohydrates cause undue fat accumulation by increasing blood insulin levels, but a more balanced diet that restricts refined carbohydrates can also reduce serum glucose and insulin levels and may also suppress lipogenesis and promote fat oxidation.^[35] However, as far as energy expenditure itself is concerned, the claim that low-carbohydrate diets have a "metabolic advantage" is not supported by clinical evidence.^[33]^[36] Further, it 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.^[37]^[38]

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.^[39]^[40]^[41] There is limited evidence to support routine use of low-carbohydrate dieting in managing type 1 diabetes.^[42] 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.^[41]

An extreme form of low-carbohydrate diet – the ketogenic diet – is established as a medical diet for treating epilepsy.^[43] Through celebrity endorsement during 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.Template:Scientific citation needed^[43] The British Dietetic Association named it one of the "top 5 worst celeb diets to avoid in 2018".^[43]

Sources

File:Glucose 2.jpg

Glucose tablets

Most dietary carbohydrates contain glucose, either as their only building block (as in the polysaccharides starch and glycogen), or together with another monosaccharide (as in the hetero-polysaccharides sucrose and lactose).^[44] 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,^[45] the roots of Ilex asprella plants in China,^[46] and straws from rice in California.^[47]

Sugar content of selected common plant foods (in grams per 100 g)^[48]
Food item	Carbohydrate, total,^A including dietary fiber	Total sugars	Free fructose	Free glucose	Sucrose	Ratio of fructose/ glucose	Sucrose as proportion of total sugars (%)
Fruits
Apple	13.8	10.4	5.9	2.4	2.1	2.0	19.9
Apricot	11.1	9.2	0.9	2.4	5.9	0.7	63.5
Banana	22.8	12.2	4.9	5.0	2.4	1.0	20.0
Fig, dried	63.9	47.9	22.9	24.8	0.9	0.93	0.15
Grapes	18.1	15.5	8.1	7.2	0.2	1.1	1
Navel orange	12.5	8.5	2.25	2.0	4.3	1.1	50.4
Peach	9.5	8.4	1.5	2.0	4.8	0.9	56.7
Pear	15.5	9.8	6.2	2.8	0.8	2.1	8.0
Pineapple	13.1	9.9	2.1	1.7	6.0	1.1	60.8
Plum	11.4	9.9	3.1	5.1	1.6	0.66	16.2
Vegetables
Beet, red	9.6	6.8	0.1	0.1	6.5	1.0	96.2
Carrot	9.6	4.7	0.6	0.6	3.6	1.0	77
Red pepper, sweet	6.0	4.2	2.3	1.9	0.0	1.2	0.0
Onion, sweet	7.6	5.0	2.0	2.3	0.7	0.9	14.3
Sweet potato	20.1	4.2	0.7	1.0	2.5	0.9	60.3
Yam	27.9	0.5	Traces	Traces	Traces	—	Traces
Sugar cane		13–18	0.2–1.0	0.2–1.0	11–16	1.0	high
Sugar beet		17–18	0.1–0.5	0.1–0.5	16–17	1.0	high
Grains
Corn, sweet	19.0	6.2	1.9	3.4	0.9	0.61	15.0

<templatestyles src="Citation/styles.css"/>^A The carbohydrate value is calculated in the USDA database and does not always correspond to the sum of the sugars, the starch, and the "dietary fiber".

Metabolism

Script error: No such module "Labelled list hatnote". 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 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 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.^[49] Energy obtained from metabolism (e.g., oxidation of glucose) is usually stored temporarily within cells in the form of ATP.^[50] Organisms capable of anaerobic and aerobic respiration metabolize glucose and oxygen (aerobic) to release energy, with carbon dioxide and water as byproducts.

Catabolism

Catabolism 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 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.^[49] In some cases, as with humans, not all carbohydrate types are usable as the digestive and metabolic enzymes necessary are not present.

Analytical tools

Many techniques are used in the analysis of glycans.^[51] NMR spectroscopy is common, the major challenge being spectral overlap.^[52] ^[53]

High-resolution mass spectrometry (MS) and high-performance liquid chromatography (HPLC)

MS and HPLC are commonly applied to glycan cleaved either enzymatically or chemically from the target.^[54] In case of glycolipids, they can be analyzed directly without separation of the lipid component.

N-glycans from glycoproteins are analyzed routinely by high-performance-liquid-chromatography (reversed phase, normal phase and ion exchange HPLC) after tagging the reducing end of the sugars with a fluorescent compound (reductive labeling).^[55] A large variety of different labels were introduced in the recent years, where 2-aminobenzamide (AB), anthranilic acid (AA), 2-aminopyridin (PA), 2-aminoacridone (AMAC) and 3-(acetylamino)-6-aminoacridine (AA-Ac) are just a few of them.^[56] Different labels have to be used for different ESI modes and MS systems used.^[57]

O-glycans are usually analysed without any tags.

Fractionated glycans from high-performance liquid chromatography (HPLC) instruments can be further analyzed by MALDI-TOF-MS(MS) to get further information about structure and purity. Sometimes glycan pools are analyzed directly by mass spectrometry without prefractionation, although a discrimination between isobaric glycan structures is more challenging or even not always possible. Anyway, direct MALDI-TOF-MS analysis can lead to a fast and straightforward illustration of the glycan pool.^[58]

High performance liquid chromatography online coupled to mass spectrometry is useful. By choosing porous graphitic carbon as a stationary phase for liquid chromatography, even non derivatized glycans can be analyzed. Detection is here done by mass spectrometry, but in instead of MALDI-MS, electrospray ionisation (ESI) is more frequently used.^[59]^[60]^[61]

Multiple reaction monitoring (MRM)

Although MRM has been used extensively in metabolomics and proteomics, its high sensitivity and linear response over a wide dynamic range make it especially suited for glycan biomarker research and discovery. MRM is performed on a triple quadrupole (QqQ) instrument, which is set to detect a predetermined precursor ion in the first quadrupole, a fragmented in the collision quadrupole, and a predetermined fragment ion in the third quadrupole. It is a non-scanning technique, wherein each transition is detected individually and the detection of multiple transitions occurs concurrently in duty cycles. This technique is being used to characterize the immune glycome.^[12]^[62]

Chemical synthesis and manipulation of carbohydrates

Carbohydrate synthesis is a sub-field of organic chemistry concerned specifically with the generation of natural and unnatural carbohydrate structures. Carbohydrate chemistry is a large and economically important branch of organic chemistry. 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 the usage of protecting groups is extensive.

Some of the main organic reactions that involve carbohydrates are:

References

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 {{short description|Organic compound that consists only of carbon, hydrogen, and oxygen}}
 {{Use mdy dates|date=September 2015}}
-[[File:Lactose.svg|thumb|class=skin-invert|upright=1.25|[[Lactose]] is a [[disaccharide]] found in animal milk. It consists of a molecule of [[galactose|D-galactose]] and a molecule of [[glucose|D-glucose]] bonded by beta-1-4 [[glycosidic linkage]].]]
+[[File:Lactose.svg|thumb|class=skin-invert-image|upright=1.25|[[Lactose]] is a [[disaccharide]] found in animal milk. It consists of a molecule of [[galactose|D-galactose]] and a molecule of [[glucose|D-glucose]] bonded by beta-1-4 [[glycosidic linkage]].]]
-A '''carbohydrate''' ({{IPAc-en|ˌ|k|ɑːr|b|oʊ|ˈ|h|aɪ|d|r|eɪ|t}}) is a [[biomolecule]] composed of [[carbon]] (C), [[hydrogen]] (H), and [[oxygen]] (O) [[atom]]s. The typical hydrogen-to-oxygen atomic ratio is 2:1, analogous to that of water, and is represented by the [[empirical formula]] {{chem2|C_{''m''}(H2O)_{''n''} }} (where ''m'' and ''n'' may differ). This formula does not imply direct covalent bonding between hydrogen and oxygen atoms; for example, in {{chem2|CH2O}}, hydrogen is covalently bonded to carbon, not oxygen. While the 2:1 hydrogen-to-oxygen ratio is characteristic of many carbohydrates, exceptions exist. For instance, [[uronic acid]]s and [[deoxy-sugar]]s like [[fucose]] deviate from this precise [[Stoichiometry|stoichiometric]] definition. Conversely, some compounds conforming to this definition, such as [[formaldehyde]] and [[acetic acid]], are not classified as carbohydrates.
+A '''carbohydrate''' ({{IPAc-en|ˌ|k|ɑːr|b|oʊ|ˈ|h|aɪ|d|r|eɪ|t}}) is a sugar (saccharide) or a sugar derivative.<ref>{{cite web |title=Carbohydrate |url=https://goldbook.iupac.org/terms/view/09809 |website=IUPAC Gold Book}}</ref> For the simplest carbohydrates, the carbon-to-hydrogen-to-oxygen atomic ratio is 1:2:1, i.e. they are often represented by the [[empirical formula]] {{chem2|C(H2O)_{''n''} }}. Together with amino acids, fats, and nucleic acids, the carbohydrates are one of the major families of biomolecules.<ref>{{cite web |url=https://www.ncbi.nlm.nih.gov/books/NBK579927/#top|title=Essentials of Glycobiology|website = National Library of Medicine}}</ref>
-The term is predominantly used in [[biochemistry]], functioning as a synonym for '''saccharide''' ({{ety|grc|''σάκχαρον'' ({{grc-transl|σάκχαρον}})|sugar}}<ref name="avenas">{{cite book |vauthors=Avenas P |year=2012 |chapter=Etymology of main polysaccharide names |veditors=Navard P |title=The European Polysaccharide Network of Excellence (EPNOE) |publisher=[[Springer Science+Business Media|Springer-Verlag]] |location=Wien |chapter-url=https://www.springer.com/cda/content/document/cda_downloaddocument/9783709104200-c1.pdf?SGWID=0-0-45-1364512-p174060193 |access-date=January 28, 2018 |archive-date=February 9, 2018 |archive-url=https://web.archive.org/web/20180209064118/https://www.springer.com/cda/content/document/cda_downloaddocument/9783709104200-c1.pdf?SGWID=0-0-45-1364512-p174060193 |url-status=dead}}</ref>), a group that includes [[sugar]]s, [[starch]], and [[cellulose]]. The saccharides are divided into four chemical groups: [[monosaccharide]]s, [[disaccharide]]s, [[oligosaccharide]]s, and [[polysaccharide]]s. Monosaccharides and disaccharides, the smallest (lower [[molecular weight]]) carbohydrates, are  commonly referred to as sugars.<ref>{{cite journal | vauthors = Flitsch SL, Ulijn RV | title = Sugars tied to the spot | journal = Nature | volume = 421 | issue = 6920 | pages = 219–220 | date = January 2003 | pmid = 12529622 | doi = 10.1038/421219a | s2cid = 4421938 | bibcode = 2003Natur.421..219F }}</ref> While 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]] ({{ety|grc|''{{wikt-lang|grc|γλεῦκος}}'' ({{grc-transl|γλεῦκος}})|wine, [[must]]}}), and is used for almost all sugars (e.g., [[fructose]] (fruit sugar), [[sucrose]] ([[Sugar cane|cane]] or [[Sugar beet|beet]] sugar), [[ribose]], [[lactose]] (milk sugar)).
+Carbohydrates perform numerous roles in living organisms.<ref>{{Lehninger4th|page=293-324}}</ref> 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]] is an important component of [[coenzyme]]s (e.g., [[Adenosine triphosphate|ATP]], [[Flavin adenine dinucleotide|FAD]] and [[Nicotinamide adenine dinucleotide|NAD]]) and the backbone of the genetic molecule known as [[RNA]]. The related [[deoxyribose]] is a component of DNA. Saccharides and their derivatives play key roles in the [[immune system]], [[fertilization]], preventing [[pathogenesis]], [[blood clotting]], and [[developmental biology|development]].<ref>{{cite book |  vauthors = Maton A, Hopkins J, McLaughlin CW, Johnson S, Warner MQ, LaHart D, Wright JD | title = Human Biology and Health | publisher = Prentice Hall | year = 1993 | location = Englewood Cliffs, New Jersey | pages = [https://archive.org/details/humanbiologyheal00scho/page/52 52–59] | isbn = 978-0-13-981176-0 | url-access = registration | url = https://archive.org/details/humanbiologyheal00scho/page/52 }}</ref>
-Carbohydrates perform numerous roles in living organisms.<ref>{{cite journal | vauthors = Carroll GT, Wang D, Turro NJ, Koberstein JT | title = Photons to illuminate the universe of sugar diversity through bioarrays | journal = Glycoconjugate Journal | volume = 25 | issue = 1 | pages = 5–10 | date = January 2008 | pmid = 17610157 | pmc = 7088275 | doi = 10.1007/s10719-007-9052-1 }}</ref> 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]] is an important component of [[coenzyme]]s (e.g., [[Adenosine triphosphate|ATP]], [[Flavin adenine dinucleotide|FAD]] and [[Nicotinamide adenine dinucleotide|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 [[developmental biology|development]].<ref>{{cite book |  vauthors = Maton A, Hopkins J, McLaughlin CW, Johnson S, Warner MQ, LaHart D, Wright JD | title = Human Biology and Health | publisher = Prentice Hall | year = 1993 | location = Englewood Cliffs, New Jersey | pages = [https://archive.org/details/humanbiologyheal00scho/page/52 52–59] | isbn = 978-0-13-981176-0 | url-access = registration | url = https://archive.org/details/humanbiologyheal00scho/page/52 }}</ref>
 Carbohydrates are central to [[nutrition]] and are found in 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 beet]]s), lactose (abundant in milk), glucose and fructose, both of which occur naturally in [[honey]], many [[fruit]]s, and some vegetables. Table sugar, milk, or honey 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]].<ref name="lpi">{{cite web|url=https://lpi.oregonstate.edu/mic/other-nutrients/fiber|title=Fiber|publisher=Micronutrient Information Center, Linus Pauling Institute, Oregon State University|date=March 2019|accessdate=19 January 2025}}</ref> Other polysaccharides contained in dietary fiber include [[resistant starch]] and [[inulin]], which feed some bacteria in the [[microbiota]] of the [[large intestine]], and are [[metabolism|metabolized]] by these bacteria to yield [[short-chain fatty acid]]s.<ref name=lpi/><ref name="CRC Handbook of Dietary Fiber in Human Nutrition">{{cite book| vauthors = Cummings JH | title=The Effect of Dietary Fiber on Fecal Weight and Composition| date=2001| publisher=CRC Press| location=Boca Raton, Florida| isbn=978-0-8493-2387-4| pages=184| edition=3rd| url=https://www.crcpress.com/CRC-Handbook-of-Dietary-Fiber-in-Human-Nutrition-Third-Edition/Spiller/p/book/9780849323874| access-date=April 24, 2022| archive-date=April 2, 2019| archive-url=https://web.archive.org/web/20190402203003/https://www.crcpress.com/CRC-Handbook-of-Dietary-Fiber-in-Human-Nutrition-Third-Edition/Spiller/p/book/9780849323874| url-status=live}}</ref><ref>{{cite journal | vauthors = Byrne CS, Chambers ES, Morrison DJ, Frost G | title = The role of short chain fatty acids in appetite regulation and energy homeostasis | journal = International Journal of Obesity | volume = 39 | issue = 9 | pages = 1331–1338 | date = September 2015 | pmid = 25971927 | pmc = 4564526 | doi = 10.1038/ijo.2015.84 }}</ref>
 ==Terminology==
-In [[scientific literature]], the term "carbohydrate" has many synonyms, like "sugar" (in the broad sense), "saccharide", "ose",<ref name="avenas"/> "glucide",<ref>{{cite book | vauthors = Fearon WF | year = 1949 | title = Introduction to Biochemistry | edition = 2nd | location = London | publisher = Heinemann | url = https://books.google.com/books?id=YkOaBQAAQBAJ | isbn = 978-1483225395 | access-date = November 30, 2017 | archive-date = July 27, 2020 | archive-url = https://web.archive.org/web/20200727175530/https://books.google.com/books?id=YkOaBQAAQBAJ | url-status = live }}</ref> "hydrate of carbon" or "[[Hydroxy group|polyhydroxy]] compounds with [[aldehyde]] or [[ketone]]". Some of these terms, especially "carbohydrate" and "sugar", are also used with other meanings.
+The term "carbohydrate" has many synonyms and the definition can depend on context.  Terms associated with carbohydrate include "sugar", "saccharide", "[[glucan]]",<ref name="avenas">{{cite book |vauthors=Avenas P |year=2012 |chapter=Etymology of main polysaccharide names |veditors=Navard P |title=The European Polysaccharide Network of Excellence (EPNOE) |publisher=[[Springer Science+Business Media|Springer-Verlag]] |location=Wien |chapter-url=https://www.springer.com/cda/content/document/cda_downloaddocument/9783709104200-c1.pdf?SGWID=0-0-45-1364512-p174060193 |access-date=January 28, 2018 |archive-date=February 9, 2018 |archive-url=https://web.archive.org/web/20180209064118/https://www.springer.com/cda/content/document/cda_downloaddocument/9783709104200-c1.pdf?SGWID=0-0-45-1364512-p174060193 }}</ref> and "glucide".<ref name="Matthews"/> In [[food science]] the term "carbohydrate" often means any food that is rich in [[starch]] (such as cereals, bread and pasta) or simple carbohydrates, or fairly simple sugars such as sucrose (found in candy, [[jam]]s, and desserts). Carbohydrates can also refer to [[dietary fiber]], like cellulose.<ref name=lpi/><ref>{{cite book | title = Carbohydrates in human nutrition | series = FAO Food and Nutrition Paper – 66 | chapter = Chapter 1 – The role of carbohydrates in nutrition | chapter-url = http://www.fao.org/docrep/w8079e/w8079e07.htm | publisher = Food and Agriculture Organization of the United Nations | access-date = December 21, 2015 | archive-date = December 22, 2015 | archive-url = https://web.archive.org/web/20151222095451/http://www.fao.org/docrep/w8079e/w8079e07.htm | url-status = live }}</ref>
-In [[food science]] and in many informal contexts, 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, [[jam]]s, and desserts).  This informality is sometimes confusing since it confounds chemical structure and digestibility in humans.
-The term "carbohydrate" (or "carbohydrate by difference") refers also to [[dietary fiber]], which is a carbohydrate, but, unlike sugars and starches, fibers are not hydrolyzed by human digestive enzymes.<ref name=lpi/> Fiber generally contributes little [[food energy]] in humans, but is often included in the calculation of total food energy. The fermentation of soluble fibers by gut microflora can yield short-chain fatty acids, and soluble fiber is estimated to provide about 2 kcal/g.<ref name=lpi/>
-== History ==
-{{Expand section|date=January 2022}}
-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.<ref>{{Cite journal |last=Denham |first=Tim |date=October 2011 |title=Early Agriculture and Plant Domestication in New Guinea and Island Southeast Asia |url=https://www.journals.uchicago.edu/doi/10.1086/658682 |journal=Current Anthropology |volume=52 |issue=54 |pages=S161–S512 |doi=10.1086/658682 |issn=0011-3204 |via=The University of Chicago Press Journals|url-access=subscription }}</ref> The term "carbohydrate" was first proposed by German chemist [[Carl Schmidt (chemist)]] in 1844. In 1856, [[glycogen]], a form of carbohydrate storage in animal livers, was discovered by French physiologist [[Claude Bernard]].<ref>{{Cite journal |last=Young |first=F. G. |date=1957-06-22 |title=Claude Bernard and the Discovery of Glycogen |journal=British Medical Journal |volume=1 |issue=5033 |pages=1431–1437 |doi=10.1136/bmj.1.5033.1431 |issn=0007-1447 |pmc=1973429 |pmid=13436813}}</ref>
-== Structure ==
-Formerly the name "carbohydrate" was used in [[chemistry]] for any compound with the formula C<sub>''m''</sub> (H<sub>2</sub>O)<sub>''n''</sub>. Following this definition, some chemists considered [[formaldehyde]] (CH<sub>2</sub>O) to be the simplest carbohydrate,<ref name="coulter">{{cite book | vauthors = Coulter JM, Barnes CR, Cowles HC | year = 1930 | url = https://books.google.com/books?id=WyZnVpCiTHIC&q=simplest+carbohydrate&pg=PA375 | title = A Textbook of Botany for Colleges and Universities | publisher = BiblioBazaar | isbn = 978-1113909954 | access-date = April 24, 2022 | archive-date = April 17, 2022 | archive-url = https://web.archive.org/web/20220417005854/https://books.google.com/books?id=WyZnVpCiTHIC&q=simplest+carbohydrate&pg=PA375 | url-status = live }}</ref> while others claimed that title for [[glycolaldehyde]].<ref name="tietz">{{cite book | vauthors = Burtis CA, Ashwood ER, Tietz NW | year = 2000 | url = https://books.google.com/books?id=l5hqAAAAMAAJ&q=simplest+carbohydrate | title = Tietz fundamentals of clinical chemistry | publisher = W.B. Saunders | isbn = 9780721686349 | access-date = January 8, 2016 | archive-date = June 24, 2016 | archive-url = https://web.archive.org/web/20160624073749/https://books.google.com/books?id=l5hqAAAAMAAJ&q=simplest+carbohydrate | url-status = live }}</ref> Today, 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., [[glycosaminoglycan]]s), [[carboxylic acid]]  and deoxy modifications (e.g., [[fucose]] and [[sialic acid]]).
-Natural saccharides are generally built of simple carbohydrates called [[monosaccharide]]s with general formula (CH<sub>2</sub>O)<sub>''n''</sub> where ''n'' is three or more. A typical monosaccharide has the structure H–(CHOH)<sub>''x''</sub>(C=O)–(CHOH)<sub>''y''</sub>–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 [[glyceraldehyde]]s. However, some biological substances commonly called "monosaccharides" do not conform to this formula (e.g., [[uronic acid]]s 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<sub>2</sub>O and [[inositol]] (CH<sub>2</sub>O)<sub>6</sub>).<ref>{{cite book | vauthors = Matthews CE, Van Holde KE, Ahern KG | year = 1999 | title = Biochemistry | edition = 3rd | publisher = Benjamin Cummings | isbn = 978-0-8053-3066-3 }}{{page needed|date=January 2018}}</ref>
-The [[open-chain]] form of a monosaccharide often coexists with a [[heterocyclic compound|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 [[polysaccharide]]s (or [[oligosaccharide]]s) 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]], 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.
-==Division==
+===Saccharides===
-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.<ref>{{cite book | title = Carbohydrates in human nutrition | series = FAO Food and Nutrition Paper – 66 | chapter = Chapter 1 – The role of carbohydrates in nutrition | chapter-url = http://www.fao.org/docrep/w8079e/w8079e07.htm | publisher = Food and Agriculture Organization of the United Nations | access-date = December 21, 2015 | archive-date = December 22, 2015 | archive-url = https://web.archive.org/web/20151222095451/http://www.fao.org/docrep/w8079e/w8079e07.htm | url-status = live }}</ref>
+The starting point for discussion of carbohydrates are the saccharides. Monosaccharides are the simplest carbohydrates in that they cannot be [[hydrolysis|hydrolyzed]] to smaller carbohydrates. Monosaccharides usually have the formula C<sub>''m''</sub> (H<sub>2</sub>O)<sub>''n''</sub>.  [[Disaccharide]]s (e.g. [[sucrose]]) are common as are [[polysaccharide]]s/[[oligosaccharide]]s (e.g., [[starch]], [[cellulose]]). Saccharides are polyhydroxy aldehydes, ketones as well as derived polymers having linkages of the [[acetal]] type. They may be classified according to their [[degree of polymerization]].  Many [[polyol]]s are also classified as carbohydrates.  In many carbohydrates the OH groups are appended to or replaced by ''N''-acetyl (e.g., [[chitin]]), [[sulfate]] (e.g., [[glycosaminoglycan]]s), [[carboxylic acid]]  and deoxy modifications (e.g., [[fucose]] and [[sialic acid]]).<ref name="Matthews">{{cite book | vauthors = Matthews CE, Van Holde KE, Ahern KG | year = 1999 | title = Biochemistry | edition = 3rd | publisher = Benjamin Cummings | isbn = 978-0-8053-3066-3 }}{{page needed|date=January 2018}}</ref>
 {| class="wikitable"
 |+ The major dietary carbohydrates
 |-
-! Class<br>(degree of polymerization) !! Subgroup !! Components
+! Class<br />(degree of polymerization) !! Subgroup !! Components
 |-
 ! rowspan=3 | [[Sugar]]s (1–2)
@@ Line 50: / Line 29: @@
 || Malto-oligosaccharides || [[Maltodextrin]]s
 |-
-| Other oligosaccharides || [[Raffinose]], [[stachyose]], fructo-oligosaccharides
+| Other oligosaccharides || [[Raffinose]], [[stachyose]], [[fructo-oligosaccharide]]s
 |-
 ! rowspan=2 | [[Polysaccharide]]s (>9)
@@ Line 58: / Line 37: @@
 |}
-==Monosaccharides==
+===Complex carbohydrates===
-{{Main|Monosaccharide}}
+[[image:Heparin General Structure V.1.svg|thumb|right|[[Heparin]], a carbohydrate, is a blood [[anticoagulant]].<ref>{{cite journal | vauthors = Alquwaizani M, Buckley L, Adams C, Fanikos J | title = Anticoagulants: A Review of the Pharmacology, Dosing, and Complications | journal = Current Emergency and Hospital Medicine Reports | volume = 1 | issue = 2 | pages = 83–97 | date = June 2013 | pmid = 23687625 | pmc = 3654192 | doi = 10.1007/s40138-013-0014-6 }}</ref>]]
+{{Main|Glycoconjugates|Glycosylation}}
+Sugars may be linked to other types of biological molecules to form [[glycoconjugate]]s. The enzymatic process of [[glycosylation]] creates sugars/saccharides linked to themselves and to other molecules by the glycosidic bond, thereby producing glycans.  [[Glycoprotein]]s, [[proteoglycan]]s and [[glycolipid]]s are the most abundant glycoconjugates found in mammalian cells. They are found predominantly on the outer cell membrane and in secreted fluids. Glycoconjugates have been shown to be important in cell-cell interactions due to the presence on the cell surface of various [[Glycan-protein interactions|glycan binding receptors]] in addition to the glycoconjugates themselves.<ref name="Ma_2004">{{cite journal |vauthors=Ma BY, Mikolajczak SA, Yoshida T, Yoshida R, Kelvin DJ, Ochi A | title= CD28 T cell costimulatory receptor function is negatively regulated by N-linked carbohydrates | journal=Biochem. Biophys. Res. Commun. | year=2004 | pages=60–7 | volume=317 | issue=1 | pmid=15047148 | doi=10.1016/j.bbrc.2004.03.012| bibcode= 2004BBRC..317...60M }}</ref><ref name="Takahashi_2004">{{cite journal |vauthors=Takahashi M, Tsuda T, Ikeda Y, Honke K, Taniguchi N | title= Role of N-glycans in growth factor signaling | journal= Glycoconj. J. | year=2004 | pages=207–12 | volume=20 | issue=3 | pmid=15090734 | doi= 10.1023/B:GLYC.0000024252.63695.5c| s2cid= 1110879 }}</ref> In addition to their function in [[protein folding]] and cellular attachment, the [[Glycans#N-Linked glycans|N-linked glycans]] of a protein can modulate the protein's function, in some cases acting as an on-off switch.<ref name = "immune_glycan"/>
-[[Image:D-glucose color coded.png|upright=0.5|thumb|class=skin-invert|[[Glucose|D-glucose]] is an aldohexose with the formula (C·H<sub>2</sub>O)<sub>6</sub>. The red atoms highlight the [[aldehyde]] group and the blue atoms highlight the [[chirality (chemistry)|asymmetric center]] furthest from the aldehyde; because this -OH is on the right of the [[Fischer projection]], this is a D sugar.]]
+== History ==
-Monosaccharides are the simplest carbohydrates in that they cannot be [[hydrolysis|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<sub>2</sub>O)<sub>n</sub>, 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.
+[[File:Baeyer-Volhard LMU 1877.jpg|thumb|[[Emil Fischer]], who elucidated the structure of [[glucose]], with colleagues and student in their laboratory of [[Ludwig Maximilian University of Munich]] in 1877.]]
+The history of carbohydrates, to some extent, is the [[history of sugar]] cane, which was first grown in [[New Guinea]].  The mass cultivation occurred in India where techniques were developed for the isolatoin of crystalline sugar.<ref>{{Cite journal |last=Denham |first=Tim |date=October 2011 |title=Early Agriculture and Plant Domestication in New Guinea and Island Southeast Asia |url=https://www.journals.uchicago.edu/doi/10.1086/658682 |journal=Current Anthropology |volume=52 |issue=54 |pages=S161–S512 |doi=10.1086/658682 |issn=0011-3204 |via=The University of Chicago Press Journals|url-access=subscription }}</ref> Cane sugar and its cultivation reached Europe around the 13th Century and then expanded to the New World, where industrialization occurred.
-===Classification of monosaccharides===
-<div class="thumb tleft">
-<div class="thumbinner" style="width:187px;">
-[[Image:Alpha-D-glucopyranose-2D-skeletal.svg|185px|class=skin-invert]]
-[[Image:Beta-D-glucopyranose-2D-skeletal.svg|185px|class=skin-invert]]
-<div class="thumbcaption">
-The [[α]] and [[Beta (letter)|β]] [[anomer]]s of glucose. Note the position of the hydroxyl group (red or green) on the anomeric carbon relative to the CH<sub>2</sub>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).<ref>{{cite book | chapter-url = https://www.ncbi.nlm.nih.gov/books/NBK1955/#_ch2_s4_ | chapter = Structural Basis of Glycan Diversity | title = Essentials of Glycobiology | edition = 3rd | publisher = Cold Spring Harbor Laboratory Press | location = Cold Spring Harbor (NY) | vauthors = Bertozzi CR, Rabuka D | isbn = 978-1-621821-32-8 | year = 2017 | pmid = 20301274 | access-date = August 30, 2017 | archive-date = May 19, 2020 | archive-url = https://web.archive.org/web/20200519081218/https://www.ncbi.nlm.nih.gov/books/NBK1955/#_ch2_s4_ | url-status = live }}</ref>
-</div>
-</div>
-</div>
-Monosaccharides are classified according to three different characteristics: the placement of its [[carbonyl]] group, the number of [[carbon]] atoms it contains, and its [[chirality (chemistry)|chiral]] handedness. If 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 [[triose]]s, those with four are called [[tetrose]]s, five are called [[pentose]]s, six are [[hexose]]s, and so on.<ref>{{cite book | vauthors = Campbell NA, Williamson B, Heyden RJ | title = Biology: Exploring Life | publisher = Pearson Prentice Hall | year = 2006 | location = Boston, Massachusetts | url = http://www.phschool.com/el_marketing.html | isbn = 978-0-13-250882-7 | access-date = December 2, 2008 | archive-date = November 2, 2014 | archive-url = https://web.archive.org/web/20141102041816/http://www.phschool.com/el_marketing.html | url-status = live }}</ref> These two systems of classification are often combined. For example, [[glucose]] is an [[aldohexose]] (a six-carbon aldehyde), [[ribose]] 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 [[Chirality (chemistry)|asymmetric]], making them [[Stereogenic|stereo center]]s with two possible configurations each (R or S). Because of this asymmetry, a number of [[isomer]]s may exist for any given monosaccharide formula. Using [[Le Bel-van't Hoff rule]], the aldohexose D-glucose, for example, has the formula (C·H<sub>2</sub>O)<sub>6</sub>, of which four of its six carbons atoms are stereogenic, making D-glucose one of 2<sup>4</sup>=16 possible [[stereoisomer]]s. In the case of [[glyceraldehyde]]s, an aldotriose, there is one pair of possible stereoisomers, which are [[enantiomers]] and [[epimer]]s. [[Dihydroxyacetone|1, 3-dihydroxyacetone]], the ketose corresponding to the aldose glyceraldehydes, is 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  [[Levorotation and dextrorotation|rotates]] plane [[Polarization (waves)|polarized light]]. This usage of "d-" and "l-" is no longer followed in carbohydrate chemistry.<ref>{{cite book | vauthors = Pigman W, Horton D | title=The Carbohydrates: Chemistry and Biochemistry Vol 1A| veditors = Pigman W, Horton D |edition=2nd|year=1972|publisher=Academic Press|location=San Diego|pages=1–67|chapter=Chapter 1: Stereochemistry of the Monosaccharides|isbn=978-0323138338}}</ref>
-===Ring-straight chain isomerism===
-[[Image:Glucose Fisher to Haworth.gif|thumb|class=skin-invert|[[Glucose]] can exist in both a straight-chain and ring form.]]
-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 the straight-chain form.<ref name=pigman>{{cite book | vauthors = Pigman W, Anet EF |title=The Carbohydrates: Chemistry and Biochemistry Vol 1A| veditors = Pigman W, Horton D  |edition=2nd|year=1972|publisher=Academic Press|location=San Diego|pages=165–194|chapter=Chapter 4: Mutarotations and Actions of Acids and Bases|isbn=978-0323138338}}</ref>
-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 [[anomer]]s. In the ''α anomer'', the -OH substituent on the anomeric carbon rests on the opposite side ([[Cis-trans isomerism|trans]]) of the ring from the CH<sub>2</sub>OH side branch. The alternative form, in which the CH<sub>2</sub>OH substituent and the anomeric hydroxyl are on the same side (cis) of the plane of the ring, is called the ''β anomer''.{{citation needed|date=April 2025}}
-===Use in living organisms===
-Monosaccharides are the major fuel source for [[metabolism]], and glucose is an energy-rich molecule utilized to generate ATP in almost all living organisms.  Glucose is a high-energy substrate produced in plants through photosynthesis by combining energy-poor water and carbon dioxide in an endothermic reaction fueled by solar energy.  When monosaccharides are not immediately needed, they are often converted to more space-efficient (i.e., less water-soluble) forms, often [[polysaccharide]]s.  In animals, glucose circulating the blood is a major metabolic substrate and is oxidized in the mitochondria to produce ATP for performing useful cellular work.  In humans and other animals, serum glucose levels must be regulated carefully to maintain glucose within acceptable limits and prevent the deleterious effects of hypo- or hyperglycemia.  Hormones such as insulin and glucagon serve to keep glucose levels in balance: insulin stimulates glucose uptake into the muscle and fat cells when glucose levels are high, whereas glucagon helps to raise glucose levels if they dip too low by stimulating hepatic glucose synthesis.  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]], is a structural component of the [[cell wall#plant cell walls|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]].<ref>{{cite encyclopedia |title=lyxoflavin |url=http://www.merriam-webster.com/medical/lyxoflavin |dictionary=Merriam-Webster |access-date=February 26, 2014 |archive-date=October 31, 2014 |archive-url=https://web.archive.org/web/20141031135041/http://www.merriam-webster.com/medical/lyxoflavin |url-status=live }}</ref> [[Ribulose]] and [[xylulose]] occur in the [[pentose phosphate pathway]]. [[Galactose]], a component of milk sugar [[lactose]], is found in [[galactolipid]]s in [[cell membrane#lipids|plant cell membranes]] and in [[glycoprotein]]s in many [[biological tissue|tissues]]. [[Mannose]] occurs in human metabolism, especially in 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.
-==Disaccharides==
-[[Image:sucrose 3Dprojection.png|thumb|[[Sucrose]], also known as table sugar, is a common disaccharide. It is composed of two monosaccharides: [[glucose|D-glucose]] (left) and [[fructose|D-fructose]] (right).]]
-{{Main|Disaccharide}}
-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 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 [[chemical formula|formula]] of unmodified disaccharides is C<sub>12</sub>H<sub>22</sub>O<sub>11</sub>. Although there are numerous kinds of disaccharides, a handful of disaccharides are particularly notable.
-[[Sucrose]], pictured to the right, is the most abundant disaccharide, and the main form in which carbohydrates are transported in plants. It is composed of one [[glucose|D-glucose]] molecule and one [[fructose|D-fructose]] molecule. The [[systematic name]] for sucrose, ''O''-α-D-glucopyranosyl-(1→2)-D-fructofuranoside, indicates four things:
-* Its monosaccharides: glucose and fructose
-* Their ring types: glucose is a [[pyranose]] and fructose is a [[furanose]]
-* How they are linked together: the oxygen on carbon number 1 (C1) of α-D-glucose is linked to the C2 of D-fructose.
-* The ''-oside'' suffix indicates that the [[anomeric carbon]] of both monosaccharides participates in the glycosidic bond.
-[[Lactose]], a disaccharide composed of one [[galactose|D-galactose]] molecule and one [[glucose|D-glucose]] molecule, occurs naturally in mammalian milk. The [[systematic name]] for lactose 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.
+The chemistry and biochemistry of carbohydrates can be traced to 1811.  On that year Constantin Kirchhoff discovered that grape sugar (glucose) forms when starch is boiled with acid. The [[starch sugar|starch industry]] started the following year. Henri Braconnot discovered in 1819 that sugar is formed through the action of [[sulfuric acid]] on cellulose. [[William Prout]], after chemical analyses of sugar and starch by [[Joseph Louis Gay-Lussac]] and Thénard, gave this group of substances the group name "[[saccharine]]." The term "carbohydrate" was first proposed by German chemist [[Carl Schmidt (chemist)]] in 1844. In 1856, [[glycogen]], a form of carbohydrate storage in animal livers, was discovered by French physiologist [[Claude Bernard]].<ref>{{Cite journal |last=Young |first=F. G. |date=1957-06-22 |title=Claude Bernard and the Discovery of Glycogen |journal=British Medical Journal |volume=1 |issue=5033 |pages=1431–1437 |doi=10.1136/bmj.1.5033.1431 |issn=0007-1447 |pmc=1973429 |pmid=13436813}}</ref>  [[Emil Fischer]] received the 1902 [[Nobel Prize in Chemistry]] for his work on sugars and [[purines]]. For the discovery of glucose metabolism, [[Otto Meyerhof]] received the 1922 [[Nobel Prize in Physiology or Medicine]]. [[Hans von Euler-Chelpin]], together with [[Arthur Harden]], received the 1929 Nobel Prize in Chemistry "for their research on sugar fermentation and the role of enzymes in this process." In 1947, both [[Bernardo Houssay]] for his discovery of the role of the [[pituitary gland]] in carbohydrate metabolism and [[Carl Ferdinand Cori|Carl]] and [[Gerty Cori]] for their discovery of the conversion of [[glycogen]] received the Nobel Prize in Physiology or Medicine. For the discovery of sugar [[nucleotides]] in carbohydrate biosynthesis, [[Luis Leloir]] received the 1970 Nobel Prize in Chemistry.
-==Oligosaccharides and polysaccharides==
+The term ''glycobiology''<ref>{{cite web |title=Essentials of Glycobiology |url=https://www.ncbi.nlm.nih.gov/books/NBK579918/ |website=National Library of Medicine |publisher=Cold Spring Harbor Laboratory Press}}</ref> was coined in 1988 by [[Raymond Dwek]] to recognize the coming together of the traditional disciplines of carbohydrate chemistry and [[biochemistry]].<ref name="rademacher">{{cite journal |vauthors=Rademacher TW, Parekh RB, Dwek RA | title=Glycobiology| journal=Annu. Rev. Biochem. | year=1988 | pages=785–838 | issue=1 | volume=57 | pmid=3052290 | doi=10.1146/annurev.bi.57.070188.004033}}</ref> This coming together was as a result of a much greater understanding of the cellular and [[molecular biology]] of [[glycan]]s. "Glycoscience" is a field that explores the structures and functions of glycans.<ref>{{cite web | title=U.S. National Research Council Report, ''Transforming Glycoscience: A Roadmap for the Future'' | url=http://dels.nas.edu/Report/Transforming-Glycoscience-Roadmap/13446 | access-date=2012-10-03 | archive-date=2014-10-20 | archive-url=https://web.archive.org/web/20141020030759/http://dels.nas.edu/Report/Transforming-Glycoscience-Roadmap/13446 }}</ref>
-===Oligosaccharides===
-{{main|Oligosaccharide}}
-Oligosaccharides are saccharide polymers composed of three to ten units of monosaccharides, connected via [[Glycosidic bond|glycosidic linkages]], similar to [[disaccharide]]s. They are usually linked to lipids or amino acids glycosic linkage with oxygen or nitrogen to form [[glycolipid]]s and [[glycoprotein]]s, though some, like the [[raffinose]] series and the [[fructooligosaccharide]]s, do not. They have roles in [[Cell–cell recognition|cell recognition]] and [[cell adhesion]].
-[[File:FOS.svg|thumb|The structure of [[fructooligosaccharide]]]]
-===Polysaccharides===
-{{main|Polysaccharides}}
 ==Nutrition==
 [[File:GrainProducts.jpg|thumb|upright|[[cereal|Grain]] products: rich sources of carbohydrates]]
-Carbohydrate consumed in food yields 3.87 kilocalories of energy per [[gram]] for simple sugars,<ref>{{cite web|url=http://ndb.nal.usda.gov/ndb/foods/show/6202|title=Show Foods|work=usda.gov|access-date=June 4, 2014|archive-date=October 3, 2017|archive-url=https://web.archive.org/web/20171003224558/https://ndb.nal.usda.gov/ndb/foods/show/6202|url-status=dead}}</ref> and 3.57 to 4.12 kilocalories per gram for complex carbohydrate in most other foods.<ref>{{cite web|url=http://www.fao.org/docrep/006/y5022e/y5022e04.htm|title=Calculation of the Energy Content of Foods – Energy Conversion Factors|work=fao.org|access-date=August 2, 2013|archive-date=May 24, 2010|archive-url=https://web.archive.org/web/20100524003622/http://www.fao.org/DOCREP/006/Y5022E/y5022e04.htm|url-status=live}}</ref> 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. Refined carbohydrates from processed foods such as white bread or rice, soft drinks, and desserts are readily digestible, and many are known to have a high glycemic index, which reflects a rapid assimilation of glucose.  By contrast, the digestion of whole, unprocessed, fiber-rich foods such as beans, peas, and whole grains produces a slower and steadier release of glucose and energy into the body.<ref>{{cite web |url=https://www.diabetes.org.uk/upload/How%20we%20help/catalogue/carb-reference-list-0511.pdf |title=Carbohydrate reference list |website=www.diabetes.org.uk |access-date=October 30, 2016 |archive-date=March 14, 2016 |archive-url=https://web.archive.org/web/20160314193016/https://www.diabetes.org.uk/upload/how%20we%20help/catalogue/carb-reference-list-0511.pdf |url-status=dead }}</ref>  Animal-based foods generally have the lowest carbohydrate levels, although milk does contain a high proportion of [[lactose]].
+Carbohydrate consumed in food yields 3.87 kilocalories of energy per [[gram]] for simple sugars,<ref>{{cite web|url=http://ndb.nal.usda.gov/ndb/foods/show/6202|title=Show Foods|work=usda.gov|access-date=June 4, 2014|archive-date=October 3, 2017|archive-url=https://web.archive.org/web/20171003224558/https://ndb.nal.usda.gov/ndb/foods/show/6202}}</ref> and 3.57 to 4.12 kilocalories per gram for complex carbohydrate in most other foods.<ref>{{cite web|url=http://www.fao.org/docrep/006/y5022e/y5022e04.htm|title=Calculation of the Energy Content of Foods – Energy Conversion Factors|work=fao.org|access-date=August 2, 2013|archive-date=May 24, 2010|archive-url=https://web.archive.org/web/20100524003622/http://www.fao.org/DOCREP/006/Y5022E/y5022e04.htm|url-status=live}}</ref> 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. Refined carbohydrates from processed foods such as white bread or rice, soft drinks, and desserts are readily digestible, and many are known to have a high glycemic index, which reflects a rapid assimilation of glucose.  By contrast, the digestion of whole, unprocessed, fiber-rich foods such as beans, peas, and whole grains produces a slower and steadier release of glucose and energy into the body.<ref>{{cite web |url=https://www.diabetes.org.uk/upload/How%20we%20help/catalogue/carb-reference-list-0511.pdf |title=Carbohydrate reference list |website=www.diabetes.org.uk |access-date=October 30, 2016 |archive-date=March 14, 2016 |archive-url=https://web.archive.org/web/20160314193016/https://www.diabetes.org.uk/upload/how%20we%20help/catalogue/carb-reference-list-0511.pdf }}</ref>  Animal-based foods generally have 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 [[monosaccharide]]s and [[disaccharide]]s but glucose is often metabolized first. In ''[[Escherichia coli]]'', for example, 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]]). [[Polysaccharide]]s are also common sources of energy. Many organisms can easily break down starches into glucose; most organisms, however, cannot metabolize [[cellulose]] or other polysaccharides such as [[chitin]] and [[arabinoxylans]]. These carbohydrate types can be metabolized by some bacteria and protists. [[Ruminant]]s and [[termite]]s, for example, use microorganisms to process cellulose, fermenting it to caloric short-chain fatty acids. Even though humans lack the enzymes to digest fiber, dietary fiber represents an important dietary element for humans.  Fibers promote healthy digestion, help regulate postprandial glucose and insulin levels, reduce cholesterol levels, and promote satiety.<ref>{{cite journal | vauthors = Pichon L, Huneau JF, Fromentin G, Tomé D | title = A high-protein, high-fat, carbohydrate-free diet reduces energy intake, hepatic lipogenesis, and adiposity in rats | journal = The Journal of Nutrition | volume = 136 | issue = 5 | pages = 1256–1260 | date = May 2006 | pmid = 16614413 | doi = 10.1093/jn/136.5.1256 | doi-access = free }}</ref>
-The [[Institute of Medicine]] recommends that American and Canadian adults get between 45 and 65% of [[food energy|dietary energy]] from whole-grain carbohydrates.<ref>Food and Nutrition Board (2002/2005). ''[https://archive.today/20070210182833/http://newton.nap.edu/books/0309085373/html Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein and Amino Acids]''. Washington, D.C.: The [[National Academies Press]]. Page [http://newton.nap.edu/books/0309085373/html/769.html 769] {{Webarchive|url=https://web.archive.org/web/20060912060636/http://newton.nap.edu/books/0309085373/html/769.html |date=September 12, 2006 }}. {{ISBN|0-309-08537-3}}.</ref> The [[Food and Agriculture Organization]] and [[World Health Organization]] jointly recommend that national dietary guidelines set a goal of 55–75% of total energy from carbohydrates, but only 10% directly from sugars (their term for simple carbohydrates).<ref>Joint WHO/FAO expert consultation (2003). ''[https://web.archive.org/web/20110423051140/http://www.who.int/hpr/NPH/docs/who_fao_expert_report.pdf]'' ([[Portable Document Format|PDF]]). Geneva: [[World Health Organization]]. pp. 55–56. {{ISBN|92-4-120916-X}}.</ref>  A 2017 [[The Cochrane Database of Systematic Reviews|Cochrane Systematic Review]] concluded that there was insufficient evidence to support the claim that whole grain diets can affect cardiovascular disease.<ref name="pmid28836672">{{cite journal | vauthors = Kelly SA, Hartley L, Loveman E, Colquitt JL, Jones HM, Al-Khudairy L, Clar C, Germanò R, Lunn HR, Frost G, Rees K | display-authors = 6 | title = Whole grain cereals for the primary or secondary prevention of cardiovascular disease | journal = The Cochrane Database of Systematic Reviews | volume = 8 | issue = 8 | pages = CD005051 | date = August 2017 | pmid = 28836672 | pmc = 6484378 | doi = 10.1002/14651858.CD005051.pub3 | url = https://spiral.imperial.ac.uk:8443/bitstream/10044/1/54579/2/Kelly_et_al-2017-.pdf | access-date = September 27, 2018 | url-status = dead | archive-url = https://web.archive.org/web/20180928044051/https://spiral.imperial.ac.uk:8443/bitstream/10044/1/54579/2/Kelly_et_al-2017-.pdf | archive-date = September 28, 2018 }}</ref>
+The [[Institute of Medicine]] recommends that American and Canadian adults get between 45 and 65% of [[food energy|dietary energy]] from whole-grain carbohydrates.<ref>Food and Nutrition Board (2002/2005). ''[https://archive.today/20070210182833/http://newton.nap.edu/books/0309085373/html Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein and Amino Acids]''. Washington, D.C.: The [[National Academies Press]]. Page [http://newton.nap.edu/books/0309085373/html/769.html 769] {{Webarchive|url=https://web.archive.org/web/20060912060636/http://newton.nap.edu/books/0309085373/html/769.html |date=September 12, 2006 }}. {{ISBN|0-309-08537-3}}.</ref> The [[Food and Agriculture Organization]] and [[World Health Organization]] jointly recommend that national dietary guidelines set a goal of 55–75% of total energy from carbohydrates, but only 10% directly from sugars (their term for simple carbohydrates).<ref>Joint WHO/FAO expert consultation (2003). ''[https://web.archive.org/web/20110423051140/http://www.who.int/hpr/NPH/docs/who_fao_expert_report.pdf]'' ([[Portable Document Format|PDF]]). Geneva: [[World Health Organization]]. pp. 55–56. {{ISBN|92-4-120916-X}}.</ref>  A 2017 [[The Cochrane Database of Systematic Reviews|Cochrane Systematic Review]] concluded that there was insufficient evidence to support the claim that whole grain diets can affect cardiovascular disease.<ref name="pmid28836672">{{cite journal | vauthors = Kelly SA, Hartley L, Loveman E, Colquitt JL, Jones HM, Al-Khudairy L, Clar C, Germanò R, Lunn HR, Frost G, Rees K | display-authors = 6 | title = Whole grain cereals for the primary or secondary prevention of cardiovascular disease | journal = The Cochrane Database of Systematic Reviews | volume = 8 | issue = 8 | article-number = CD005051 | date = August 2017 | pmid = 28836672 | pmc = 6484378 | doi = 10.1002/14651858.CD005051.pub3 | url = https://spiral.imperial.ac.uk:8443/bitstream/10044/1/54579/2/Kelly_et_al-2017-.pdf | access-date = September 27, 2018 | archive-url = https://web.archive.org/web/20180928044051/https://spiral.imperial.ac.uk:8443/bitstream/10044/1/54579/2/Kelly_et_al-2017-.pdf | archive-date = September 28, 2018 }}</ref>
+Carbohydrates are 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]].<ref name="lpi">{{cite web|url=https://lpi.oregonstate.edu/mic/other-nutrients/fiber|title=Fiber|publisher=Micronutrient Information Center, Linus Pauling Institute, Oregon State University|date=March 2019|access-date=19 January 2025}}</ref> Other polysaccharides contained in dietary fiber include [[resistant starch]] and [[inulin]], which feed some bacteria in the [[microbiota]] of the [[large intestine]], and are [[metabolism|metabolized]] by these bacteria to yield [[short-chain fatty acid]]s.<ref name=lpi/><ref name="CRC Handbook of Dietary Fiber in Human Nutrition">{{cite book| vauthors = Cummings JH | title=The Effect of Dietary Fiber on Fecal Weight and Composition| date=2001| publisher=CRC Press| location=Boca Raton, Florida| isbn=978-0-8493-2387-4| page=184| edition=3rd| url=https://www.crcpress.com/CRC-Handbook-of-Dietary-Fiber-in-Human-Nutrition-Third-Edition/Spiller/p/book/9780849323874| access-date=April 24, 2022| archive-date=April 2, 2019| archive-url=https://web.archive.org/web/20190402203003/https://www.crcpress.com/CRC-Handbook-of-Dietary-Fiber-in-Human-Nutrition-Third-Edition/Spiller/p/book/9780849323874| url-status=live}}</ref><ref>{{cite journal | vauthors = Byrne CS, Chambers ES, Morrison DJ, Frost G | title = The role of short chain fatty acids in appetite regulation and energy homeostasis | journal = International Journal of Obesity | volume = 39 | issue = 9 | pages = 1331–1338 | date = September 2015 | pmid = 25971927 | pmc = 4564526 | doi = 10.1038/ijo.2015.84 }}</ref>
 ===Classification===<!-- This title is used as a redirect target -->
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 <!-- weight -->
-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.<ref name=endo>{{cite journal | vauthors = Schwartz MW, Seeley RJ, Zeltser LM, Drewnowski A, Ravussin E, Redman LM, Leibel RL | title = Obesity Pathogenesis: An Endocrine Society Scientific Statement | journal = Endocrine Reviews | volume = 38 | issue = 4 | pages = 267–296 | date = August 2017 | pmid = 28898979 | pmc = 5546881 | doi = 10.1210/er.2017-00111 }}</ref> 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 the amount of fat vs carbohydrate in the diet."<ref name=endo/> In the long term, low-carbohydrate diets do not appear to confer a "metabolic advantage," and effective weight loss or maintenance depends on the level of [[calorie restriction]],<ref name=endo/> not the ratio of [[macronutrient]]s in a diet.<ref name=tob>{{cite book |chapter=Behavioral approaches to the treatment of obesity |vauthors=Butryn ML, Clark VL, Coletta MC |title=Textbook of Obesity | veditors = Akabas SR, Lederman SA, Moore BJ |publisher=John Wiley & Sons|location=New York|year=2012 |quote=Taken together, these findings indicate that calorie intake, not macronutrient composition, determines long-term weight loss maintenance.|isbn=978-0-470-65588-7|page=259}}</ref> The reasoning of diet advocates that carbohydrates cause undue fat accumulation by increasing blood [[insulin]] levels, but a more balanced diet that restricts refined carbohydrates can also reduce serum glucose and insulin levels and may also suppress lipogenesis and promote fat oxidation.<ref>{{cite journal | vauthors =  Lopes da Silva MV, de Cassia Goncalves Alfenas R | title = Effect of the glycemic index on lipid oxidation and body composition | journal = Nutrición Hospitalaria | volume = 26 | issue = 1| pages = 48–55 | date = 2011 | doi = 10.3305/nh.2011.26.1.5008 | pmid = 21519729 }}</ref>  However, as far as energy expenditure itself is concerned, the claim that low-carbohydrate diets have a "metabolic advantage" is not supported by [[evidence-based medicine|clinical evidence]].<ref name=endo/><ref name=hall>{{cite journal | vauthors = Hall KD | title = A review of the carbohydrate-insulin model of obesity | journal = European Journal of Clinical Nutrition | volume = 71 | issue = 3 | pages = 323–326 | date = March 2017 | pmid = 28074888 | doi = 10.1038/ejcn.2016.260 | type = Review | s2cid = 54484172 }}</ref> Further, it 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.<ref name=man>{{cite journal | vauthors = Mansoor N, Vinknes KJ, Veierød MB, Retterstøl K | title = Effects of low-carbohydrate diets v. low-fat diets on body weight and cardiovascular risk factors: a meta-analysis of randomised controlled trials | journal = The British Journal of Nutrition | volume = 115 | issue = 3 | pages = 466–479 | date = February 2016 | pmid = 26768850 | doi = 10.1017/S0007114515004699 | s2cid = 21670516 | doi-access = free }}</ref><ref name=ght>{{cite journal | vauthors = Gjuladin-Hellon T, Davies IG, Penson P, Amiri Baghbadorani R | title = Effects of carbohydrate-restricted diets on low-density lipoprotein cholesterol levels in overweight and obese adults: a systematic review and meta-analysis | journal = Nutrition Reviews | volume = 77 | issue = 3 | pages = 161–180 | date = March 2019 | pmid = 30544168 | doi = 10.1093/nutrit/nuy049 | url = http://researchonline.ljmu.ac.uk/id/eprint/8898/1/nutr-rev%20corrected%20version%2007072018.pdf | access-date = April 24, 2022 | url-status = live | type = Systematic review | s2cid = 56488132 | doi-access = free | archive-url = https://web.archive.org/web/20200506070047/http://researchonline.ljmu.ac.uk/id/eprint/8898/1/nutr-rev%20corrected%20version%2007072018.pdf | archive-date = May 6, 2020 }}</ref>
+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.<ref name=endo>{{cite journal | vauthors = Schwartz MW, Seeley RJ, Zeltser LM, Drewnowski A, Ravussin E, Redman LM, Leibel RL | title = Obesity Pathogenesis: An Endocrine Society Scientific Statement | journal = Endocrine Reviews | volume = 38 | issue = 4 | pages = 267–296 | date = August 2017 | pmid = 28898979 | pmc = 5546881 | doi = 10.1210/er.2017-00111 }}</ref> 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 the amount of fat vs carbohydrate in the diet."<ref name=endo/> In the long term, low-carbohydrate diets do not appear to confer a "metabolic advantage," and effective weight loss or maintenance depends on the level of [[calorie restriction]],<ref name=endo/> not the ratio of [[macronutrient]]s in a diet.<ref name=tob>{{cite book |chapter=Behavioral approaches to the treatment of obesity |vauthors=Butryn ML, Clark VL, Coletta MC |title=Textbook of Obesity | veditors = Akabas SR, Lederman SA, Moore BJ |publisher=John Wiley & Sons|location=New York|year=2012 |quote=Taken together, these findings indicate that calorie intake, not macronutrient composition, determines long-term weight loss maintenance.|isbn=978-0-470-65588-7|page=259}}</ref> The reasoning of diet advocates that carbohydrates cause undue fat accumulation by increasing blood [[insulin]] levels, but a more balanced diet that restricts refined carbohydrates can also reduce serum glucose and insulin levels and may also suppress lipogenesis and promote fat oxidation.<ref>{{cite journal | vauthors =  Lopes da Silva MV, de Cassia Goncalves Alfenas R | title = Effect of the glycemic index on lipid oxidation and body composition | journal = Nutrición Hospitalaria | volume = 26 | issue = 1| pages = 48–55 | date = 2011 | doi = 10.3305/nh.2011.26.1.5008 | doi-broken-date = September 5, 2025 | pmid = 21519729 }}</ref>  However, as far as energy expenditure itself is concerned, the claim that low-carbohydrate diets have a "metabolic advantage" is not supported by [[evidence-based medicine|clinical evidence]].<ref name=endo/><ref name=hall>{{cite journal | vauthors = Hall KD | title = A review of the carbohydrate-insulin model of obesity | journal = European Journal of Clinical Nutrition | volume = 71 | issue = 3 | pages = 323–326 | date = March 2017 | pmid = 28074888 | doi = 10.1038/ejcn.2016.260 | type = Review | s2cid = 54484172 }}</ref> Further, it 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.<ref name=man>{{cite journal | vauthors = Mansoor N, Vinknes KJ, Veierød MB, Retterstøl K | title = Effects of low-carbohydrate diets v. low-fat diets on body weight and cardiovascular risk factors: a meta-analysis of randomised controlled trials | journal = The British Journal of Nutrition | volume = 115 | issue = 3 | pages = 466–479 | date = February 2016 | pmid = 26768850 | doi = 10.1017/S0007114515004699 | s2cid = 21670516 | doi-access = free }}</ref><ref name=ght>{{cite journal | vauthors = Gjuladin-Hellon T, Davies IG, Penson P, Amiri Baghbadorani R | title = Effects of carbohydrate-restricted diets on low-density lipoprotein cholesterol levels in overweight and obese adults: a systematic review and meta-analysis | journal = Nutrition Reviews | volume = 77 | issue = 3 | pages = 161–180 | date = March 2019 | pmid = 30544168 | doi = 10.1093/nutrit/nuy049 | url = http://researchonline.ljmu.ac.uk/id/eprint/8898/1/nutr-rev%20corrected%20version%2007072018.pdf | access-date = April 24, 2022 | url-status = live | type = Systematic review | s2cid = 56488132 | doi-access = free | archive-url = https://web.archive.org/web/20200506070047/http://researchonline.ljmu.ac.uk/id/eprint/8898/1/nutr-rev%20corrected%20version%2007072018.pdf | archive-date = May 6, 2020 }}</ref>
 <!-- diabetes -->
@@ Line 215: / Line 156: @@
 In glycolysis, oligo- and polysaccharides are cleaved first to smaller monosaccharides by enzymes called [[glycoside hydrolase]]s. The monosaccharide units can then enter into monosaccharide catabolism. A 2&nbsp;ATP investment is required in the early steps of glycolysis to phosphorylate Glucose to [[Glucose 6-phosphate|Glucose 6-Phosphate]] ([[Glucose 6-phosphate|G6P]]) and [[Fructose 6-phosphate|Fructose 6-Phosphate]] ([[Fructose 6-phosphate|F6P]]) to [[Fructose 1,6-bisphosphate|Fructose 1,6-biphosphate]] ([[Fructose 1,6-bisphosphate|FBP]]), thereby pushing the reaction forward irreversibly.<ref name="Maughan"/> In some cases, as with humans, not all carbohydrate types are usable as the digestive and metabolic enzymes necessary are not present.
-==Carbohydrate chemistry==
+==Analytical tools==
-Carbohydrate chemistry is a large and economically important branch of organic chemistry. Some of the main [[organic reaction]]s that involve carbohydrates are:
+Many techniques are used in the analysis of glycans.<ref name="Cold Spring Harbor Laboratory Press">{{cite book |title=Essentials of Glycobiology |publisher=Cold Spring Harbor Laboratory Press |edition=2nd |year=2009 |isbn=978-0-87969-770-9  |url=http://www.cshlpress.com/default.tpl?action=full&--eqskudatarq=666}}</ref> [[NMR spectroscopy]] is common, the major challenge being spectral overlap.<ref>{{cite journal |last1=Fontana |first1=Carolina |last2=Widmalm |first2=Göran |title=Primary Structure of Glycans by NMR Spectroscopy |journal=Chemical Reviews |date=2023 |volume=123 |issue=3 |pages=1040–1102 |doi=10.1021/acs.chemrev.2c00580 |pmid=36622423 |pmc=9912281 }}</ref>
+<ref>{{Cite journal|last1=Aizpurua-Olaizola|first1=O.|last2=Toraño|first2=J. Sastre|last3=Falcon-Perez|first3=J.M.|last4=Williams|first4=C.|last5=Reichardt|first5=N.|last6=Boons|first6=G.-J.|title=Mass spectrometry for glycan biomarker discovery|journal=TrAC Trends in Analytical Chemistry|volume=100|pages=7–14|doi=10.1016/j.trac.2017.12.015|year=2018|hdl=1874/364403 |hdl-access=free}}</ref>
+===High-resolution mass spectrometry (MS) and high-performance liquid chromatography (HPLC)===
+[[Mass spectrometry|MS]] and [[high-performance liquid chromatography|HPLC]] are commonly applied to glycan cleaved either enzymatically or chemically from the target.<ref>{{cite journal  |vauthors=Wada Y, Azadi P, Costello CE, etal |title=Comparison of the methods for profiling glycoprotein glycans—HUPO Human Disease Glycomics/Proteome Initiative multi-institutional study |journal=Glycobiology |volume=17 |issue=4 |pages=411–22 |date=April 2007 |pmid=17223647 |doi=10.1093/glycob/cwl086 |doi-access=free }}</ref> In case of glycolipids, they can be analyzed directly without separation of the lipid component.
+N-[[glycans]] from glycoproteins are analyzed routinely by high-performance-liquid-chromatography (reversed phase, normal phase and ion exchange HPLC) after tagging the reducing end of the sugars with a fluorescent compound (reductive labeling).<ref>{{cite journal |vauthors=Hase S, Ikenaka T, Matsushima Y |title=Structure analyses of oligosaccharides by tagging of the reducing end sugars with a fluorescent compound |journal=Biochem. Biophys. Res. Commun. |volume=85 |issue=1 |pages=257–63 |date=November 1978 |pmid=743278 |doi=10.1016/S0006-291X(78)80037-0 |bibcode=1978BBRC...85..257H }}</ref>
+A large variety of different labels were introduced in the recent years, where 2-aminobenzamide (AB), anthranilic acid (AA), 2-aminopyridin (PA), 2-aminoacridone (AMAC) and 3-(acetylamino)-6-aminoacridine (AA-Ac) are just a few of them.<ref>{{cite journal  |vauthors=Pabst M, Kolarich D, Pöltl G, etal |title=Comparison of fluorescent labels for oligosaccharides and introduction of a new postlabeling purification method |journal=Anal. Biochem. |volume=384 |issue=2 |pages=263–73 |date=January 2009 |pmid=18940176 |doi=10.1016/j.ab.2008.09.041 }}</ref> Different labels have to be used for different ESI modes and MS systems used.<ref>{{Cite journal |last1=Šoić |first1=Dinko |last2=Mlinarić |first2=Zvonimir |last3=Lauc |first3=Gordan |last4=Gornik |first4=Olga |last5=Novokmet |first5=Mislav |last6=Keser |first6=Toma |date=2022 |title=In a pursuit of optimal glycan fluorescent label for negative MS mode for high-throughput N-glycan analysis |journal=Frontiers in Chemistry |volume=10 |article-number=999770 |doi=10.3389/fchem.2022.999770 |pmid=36262345 |pmc=9574008 |bibcode=2022FrCh...10.9770S |issn=2296-2646|doi-access=free }}</ref>
+O-[[glycans]] are usually analysed without any tags.
+Fractionated glycans from [[high-performance liquid chromatography]] (HPLC) instruments can be further analyzed by [[MALDI]]-TOF-MS(MS) to get further information about structure and purity. Sometimes glycan pools are analyzed directly by [[mass spectrometry]] without prefractionation, although a discrimination between isobaric glycan structures is more challenging or even not always possible. Anyway, direct [[MALDI]]-TOF-MS analysis can lead to a fast and straightforward illustration of the glycan pool.<ref>{{cite journal |vauthors=Harvey DJ, Bateman RH, Bordoli RS, Tyldesley R |title=Ionisation and fragmentation of complex glycans with a quadrupole time-of-flight mass spectrometer fitted with a matrix-assisted laser desorption/ionisation ion source |journal=Rapid Commun. Mass Spectrom. |volume=14 |issue=22 |pages=2135–42 |year=2000 |pmid=11114021 |doi=10.1002/1097-0231(20001130)14:22<2135::AID-RCM143>3.0.CO;2-# |bibcode=2000RCMS...14.2135H }}</ref>
+High performance liquid chromatography online coupled to mass spectrometry is useful. By choosing porous graphitic carbon as a stationary phase for liquid chromatography, even non derivatized glycans can be analyzed. Detection is here done by mass spectrometry, but in instead of [[MALDI]]-MS, electrospray ionisation ([[Electrospray ionization|ESI]]) is more frequently used.<ref>{{cite journal|last1=Schulz|first1=BL|last2=Packer NH|first2=NH|last3=Karlsson|first3=NG|title=Small-scale analysis of O-linked oligosaccharides from glycoproteins and mucins separated by gel electrophoresis.|journal=Anal. Chem.|volume=74|issue=23|pages=6088–97|pmid=12498206|doi=10.1021/ac025890a|date=Dec 2002}}</ref><ref>{{cite journal |vauthors=Pabst M, Bondili JS, Stadlmann J, Mach L, Altmann F |title=Mass plus retention time equals structure: a strategy for the analysis of N-glycans by carbon LC-ESI-MS and its application to fibrin N-glycans |journal=Anal. Chem. |volume=79 |issue=13 |pages=5051–7 |date=July 2007 |pmid=17539604 |doi=10.1021/ac070363i }}</ref><ref>{{cite journal |vauthors=Ruhaak LR, Deelder AM, Wuhrer M |title=Oligosaccharide analysis by graphitized carbon liquid chromatography-mass spectrometry |journal=Anal Bioanal Chem |volume=394 |issue=1 |pages=163–74 |date=May 2009 |pmid=19247642 |doi=10.1007/s00216-009-2664-5 |doi-access=free }}</ref>
+===Multiple reaction monitoring (MRM)===
+Although MRM has been used extensively in metabolomics and proteomics, its high sensitivity and linear response over a wide dynamic range make it especially suited for glycan biomarker research and discovery. MRM is performed on a triple quadrupole (QqQ) instrument, which is set to detect a predetermined precursor ion in the first quadrupole, a fragmented in the collision quadrupole, and a predetermined fragment ion in the third quadrupole. It is a non-scanning technique, wherein each transition is detected individually and the detection of multiple transitions occurs concurrently in duty cycles. This technique is being used to characterize the immune glycome.<ref name = "immune_glycan"/><ref>{{Cite journal|last1=Flowers|first1=Sarah A.|last2=Ali|first2=Liaqat|last3=Lane|first3=Catherine S.|last4=Olin|first4=Magnus|last5=Karlsson|first5=Niclas G.|date=2013-04-01|title=Selected reaction monitoring to differentiate and relatively quantitate isomers of sulfated and unsulfated core 1 O-glycans from salivary MUC7 protein in rheumatoid arthritis|journal=Molecular & Cellular Proteomics|volume=12|issue=4|pages=921–931|doi=10.1074/mcp.M113.028878|doi-access=free |issn=1535-9484|pmc=3617339|pmid=23457413}}</ref>
+==Chemical synthesis and manipulation of carbohydrates==
+[[Carbohydrate synthesis]] is a sub-field of [[organic chemistry]] concerned specifically with the generation of natural and unnatural carbohydrate structures. Carbohydrate chemistry is a large and economically important branch of organic chemistry. This can include the synthesis of [[monosaccharide]] residues or structures containing more than one monosaccharide, known as [[oligosaccharides]]. Selective formation of [[Glycosidic bond|glycosidic linkages]] and selective reactions of [[Hydroxy group|hydroxyl groups]] are very important, and the usage of [[protecting group]]s is extensive.
+Some of the main [[organic reaction]]s that involve carbohydrates are:
 * [[Amadori rearrangement]]
 * [[Carbohydrate acetalisation]]
@@ Line 229: / Line 191: @@
 * [[Ferrier II reaction]]
-==Chemical synthesis==
-{{Main|Carbohydrate synthesis}}
-[[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 bond|glycosidic linkages]] and selective reactions of [[Hydroxy group|hydroxyl groups]] are very important, and the usage of [[protecting group]]s is extensive.
-Common reactions for glycosidic bond formation are as follows:
-* [[Chemical glycosylation]]
-* [[Fischer glycosidation]]
-* [[Koenigs-Knorr reaction]]
-* [[Crich beta-mannosylation]]
-While some common protection methods are as below:
-* [[Carbohydrate acetalisation]]
-* [[Trimethylsilyl]]
-* [[Benzyl]] ether
-* [[P-methoxybenzyl|p-Methoxybenzyl]] ether
-== See also ==
 <!-- Please keep alphabetical -->
-* [[Bioplastic]]
+Related topics
 * [[Carbohydrate NMR]]
+==See also==
 * [[Gluconeogenesis]] – A process where glucose can be synthesized by non-carbohydrate sources.
 * [[Glycobiology]]

Carbohydrate: Difference between revisions

Latest revision as of 13:16, 4 November 2025

Contents

Terminology

Saccharides

Complex carbohydrates

History

Nutrition

Classification

Glycemic index

Health effects of dietary carbohydrate restriction

Sources

Metabolism

Catabolism

Analytical tools

High-resolution mass spectrometry (MS) and high-performance liquid chromatography (HPLC)

Multiple reaction monitoring (MRM)

Chemical synthesis and manipulation of carbohydrates

See also

References

Further reading

External links

Navigation menu

Carbohydrate: Difference between revisions

Latest revision as of 13:16, 4 November 2025

Terminology

Saccharides

Complex carbohydrates

History

Nutrition

Classification

Glycemic index

Health effects of dietary carbohydrate restriction

Sources

Metabolism

Catabolism

Analytical tools

High-resolution mass spectrometry (MS) and high-performance liquid chromatography (HPLC)

Multiple reaction monitoring (MRM)

Chemical synthesis and manipulation of carbohydrates

See also

References

Further reading

External links

Navigation menu

Search