Disaccharides And Polysaccharides
- [Voiceover] All right. In a previous video, I talked about how cyclic monosaccharides, like this green cyclic glucose, can react with alcohols, like this pink alcohol, to form acetals and ketals. I believe that I mentioned that sometimes the alcohol that comes in and is reduced is actually another carbohydrate. Let me draw this in here. It makes sense, because what you see, with carbohydrates, is that they're chock full of hydroxilate groups. They're chock full of these OH groups. So, really, they can function really similarly to alcohol in reactions. When this happens, the individual monosaccharides are linked together to make an acetal. We call this linkage a glycosidic linkage. This is a glycosidic, a glycosidic linkage. Now, when two monosaccharides are linked together in this fashion, by glycosidic linkages, we call the product a disaccharide. A disaccharide. We have "di," which means two, and "saccharide," which means sugar. So sugar. So two monosaccharides linked together, they're called a disaccharide. Now, with disaccharides, most commonly the glycosidic linkage forms between the anomaric carbon, or C1 ... Remember, this is the anomeric carbon. That's C1. Over in our glycosite here, it'd be right here, just the same, we got C1 of the first sugar. Then, C4 of the second sugar, so right here would be C4, and it's just the same over here. So right here we have C4. That's the second sugar. So we call this a one, four glycosidic linkage. Then, just like we could further break down our monosaccharides into alpha and beta based off the orientation of the anomeric hydroxyl group, we can more specifically call the one, four linkage an alpha or a beta linkage, again, based off what is now the orientation of the OR group on the anomeric carbon. Same rules apply. If the Continue reading >>
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Sugars: The Difference Between Fructose, Glucose And Sucrose
29/06/2016 7:43 AM AEST | Updated 15/07/2016 12:56 PM AEST Sugars: The Difference Between Fructose, Glucose And Sucrose We're not just confused, we're also misinformed. "Fructose is the worst for you." "No way, sucrose is the devil." "I don't eat any sugar." Sugar is confusing. While some people only use certain types of sugars, others dismiss them completely. But is this necessary, or even grounded? To help settle the confusion, we spoke to Alan Barclay -- accredited practising dietitian, spokesperson for the Dietitians Association of Australia and Chief Scientific Officer at the Glycemic Index Foundation . "All the sugars are used as a source of fuel, but there are subtle differences in the way they are digested and absorbed," Barclay said. "In foods in Australia, the most common sugars are monosaccharides (glucose, fructose and galactose), but mostly these are occurring as disaccharides (which are sucrose, lactose and maltose)." Monosaccharides and disaccharides are two kinds of simple sugars, which are a form of carbohydrate. Oligosaccharides and polysaccharides, on the other hand, contain more sugar combinations and are known as complex carbohydrates -- for example, whole grain breads, brown rice and sweet potatoes. Monosaccharides require the least effort by the body to break down, meaning they are available for energy more quickly than disaccharides. "Monosaccharides don't require any digestion and can be absorbed into the mouth," Barclay said. "The problem there is they can cause dental caries which is one of the primary reasons why we need to be careful of how much added sugar we're consuming." Glucose -- the body's main source of energy and is found in fruit such as pasta, whole grain bread, legumes and a range of vegetables. Fructose -- this 'fruit sugar' fo Continue reading >>
Complex Carbohydrates Are Formed By Linkage Of Monosaccharides
Because sugars contain many hydroxyl groups, glycosidic bonds can join one monosaccharide to another. Oligosaccharides are built by the linkage of two or more monosaccharides by O-glycosidic bonds (Figure 11.10). In maltose, for example, two d-glucose residues are joined by a glycosidic linkage between the α-anomeric form of C-1 on one sugar and the hydroxyl oxygen atom on C-4 of the adjacent sugar. Such a linkage is called an α-1,4-glycosidic bond. The fact that monosaccharides have multiple hydroxyl groups means that various glycosidic linkages are possible. Indeed, the wide array of these linkages in concert with the wide variety of monosaccharides and their many isomeric forms makes complex carbohydrates information-rich molecules. Go to: 11.2.1. Sucrose, Lactose, and Maltose Are the Common Disaccharides A disaccharide consists of two sugars joined by an O-glycosidic bond. Three abundant disaccharides are sucrose, lactose, and maltose (Figure 11.11). Sucrose (common table sugar) is obtained commercially from cane or beet. The anomeric carbon atoms of a glucose unit and a fructose unit are joined in this disaccharide; the configuration of this glycosidic linkage is α for glucose and β for fructose. Sucrose can be cleaved into its component monosaccharides by the enzyme sucrase. Lactose, the disaccharide of milk, consists of galactose joined to glucose by a β-1,4-glycosidic linkage. Lactose is hydrolyzed to these monosaccharides by lactase in human beings (Section 16.1.12) and by β-galactosidase in bacteria. In maltose, two glucose units are joined by an α-1,4 glycosidic linkage, as stated earlier. Maltose comes from the hydrolysis of starch and is in turn hydrolyzed to glucose by maltase. Sucrase, lactase, and maltase are located on the outer surfaces of epith Continue reading >>
Principles Of Biochemistry/the Carbohydrates: Monosaccharides, Disaccharides And Polysaccharides
Principles of Biochemistry/The Carbohydrates: Monosaccharides, Disaccharides and Polysaccharides From Wikibooks, open books for an open world Earlier the name "carbohydrate" was used in chemistry for any compound with the formula Cm(H2O)n. Following this definition, some chemists considered formaldehyde CH2O to be the simplest carbohydrate, while others claimed that title for glycolaldehyde. Today the term is generally understood in the biochemistry sense, which excludes compounds with only one or two carbons. Natural saccharides are generally built of simple carbohydrates called monosaccharides with general formula (CH2O)n where n is three or more. A typical monosaccharide has the structure H-(CHOH)x(C=O)-(CHOH)y-H, that is, an aldehyde or ketone with many hydroxyl groups added, usually one on each carbon atom that is not part of the aldehyde or ketone functional group . Examples of monosaccharides are glucose , fructose, and glyceraldehyde. However, some biological substances commonly called "monosaccharides" do not conform to this formula (e.g., uronic acids and deoxy-sugars such as fucose ), and there are many chemicals that do conform to this formula but are not considered to be monosaccharides (e.g., formaldehyde CH2O and inositol (CH2O)6). 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 polysaccharides (or oligosaccharides) in a large variety of ways. Many carbohydrates contain one or more modified monosaccharide units that have had one or more groups replaced or removed. For example, deoxyribose, a component of DNA, is Continue reading >>
Carbohydrates
Carbohydrates have the general molecular formula CH2O, and thus were once thought to represent "hydrated carbon". However, the arrangement of atoms in carbohydrates has little to do with water molecules. Starch and cellulose are two common carbohydrates. Both are macromolecules with molecular weights in the hundreds of thousands. Both are polymers (hence "polysaccharides"); that is, each is built from repeating units, monomers, much as a chain is built from its links. The monomers of both starch and cellulose are the same: units of the sugar glucose. Sugars Monosaccharides Three common sugars share the same molecular formula: CHO. Because of their six carbon atoms, each is a hexose. They are: glucose, "blood sugar", the immediate source of energy for cellular respiration galactose, a sugar in milk (and yogurt), and fructose, a sugar found in honey. Although all three share the same molecular formula (C6H12O6), the arrangement of atoms differs in each case. Substances such as these three, which have identical molecular formulas but different structural formulas, are known as structural isomers. Glucose, galactose, and fructose are "single" sugars or monosaccharides. Two monosaccharides can be linked together to form a "double" sugar or disaccharide. Disaccharides Three common disaccharides: sucrose — common table sugar = glucose + fructose lactose — major sugar in milk = glucose + galactose maltose — product of starch digestion = glucose + glucose Although the process of linking the two monomers is rather complex, the end result in each case is the loss of a hydrogen atom (H) from one of the monosaccharides and a hydroxyl group (OH) from the other. The resulting linkage between the sugars is called a glycosidic bond. The molecular formula of each of these disacchar Continue reading >>
Disaccharide
Sucrose, a disaccharide formed from condensation of a molecule of glucose and a molecule of fructose A disaccharide (also called a double sugar or biose[1]) is the sugar formed when two monosaccharides (simple sugars) are joined by glycosidic linkage. Like monosaccharides, disaccharides are soluble in water. Three common examples are sucrose, lactose,[2] and maltose. Disaccharides are one of the four chemical groupings of carbohydrates (monosaccharides, disaccharides, oligosaccharides, and polysaccharides). The most common types of disaccharides—sucrose, lactose, and maltose—have twelve carbon atoms, with the general formula C12H22O11. The differences in these disaccharides are due to atomic arrangements within the molecule.[3] The joining of simple sugars into a double sugar happens by a condensation reaction, which involves the elimination of a water molecule from the functional groups only. Breaking apart a double sugar into its two simple sugars is accomplished by hydrolysis with the help of a type of enzyme called a disaccharidase. As building the larger sugar ejects a water molecule, breaking it down consumes a water molecule. These reactions are vital in metabolism. Each disaccharide is broken down with the help of a corresponding disaccharidase (sucrase, lactase, and maltase). Classification[edit] There are two functionally different classes of disaccharides: Reducing disaccharides, in which one monosaccharide, the reducing sugar of the pair, still has a free hemiacetal unit that can perform as a reducing aldehyde group; cellobiose and maltose are examples of reducing disaccharides, each with one hemiacetal unit, the other occupied by the glycosidic bond, which prevents it from acting as a reducing agent. Non-reducing disaccharides, in which the component mo Continue reading >>
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What’s in a spud? Besides water, which makes up most of the potato’s weight, there’s a little fat, a little protein…and a whole lot of carbohydrate (about 37 grams in a medium potato). Some of that carbohydrate is in the form of sugars. These provide the potato, and the person eating the potato, with a ready fuel source. A bit more of the potato's carbohydrate is in the form of fiber, including cellulose polymers that give structure to the potato’s cell walls. Most of the carbohydrate, though, is in the form of starch, long chains of linked glucose molecules that are a storage form of fuel. When you eat French fries, potato chips, or a baked potato with all the fixings, enzymes in your digestive tract get to work on the long glucose chains, breaking them down into smaller sugars that your cells can use. Carbohydrates are biological molecules made of carbon, hydrogen, and oxygen in a ratio of roughly one carbon atom (C) to one water molecule (HO). This composition gives carbohydrates their name: they are made up of carbon (carbo-) plus water (-hydrate). Carbohydrate chains come in different lengths, and biologically important carbohydrates belong to three categories: monosaccharides, disaccharides, and polysaccharides. In this article, we’ll learn more about each type of carbohydrates, as well as the essential energetic and structural roles they play in humans and other organisms. If the sugar has an aldehyde group, meaning that the carbonyl C is the last one in the chain, it is known as an aldose. If the carbonyl C is internal to the chain, so that there are other carbons on both sides of it, it forms a ketone group and the sugar is called a ketose. Sugars are also named according to their number of carbons: some of the most common types are trioses (thre Continue reading >>
Glucose And Disaccharide-sensing Mechanisms Modulate The Expression Of -amylase In Barley Embryos1
Metabolism is defined as the ability of the disaccharides to induce an increase in the endogenous content of Glc+Fru+Suc equal to or exceeding two times that of control, as well as in bringing about a significant (two times that of control) increase in the dry wt of the isolated embryos. Data on -amylase repression are based on the ability of the tested disaccharides (80 mm) to repress -amylase induction by at least 70%. The Fru moiety of lactulose/palatinose/turanose is linked to Gal/Glc/Glc through position 4/6/3 respectively (Table (TableI),I ), suggesting that positions 4/6/3 of the Fru moiety do not play an important role in the molecular recognition of the disaccharides. We tested if C4 and C3 epimers of Fru (tagatose and psicose) could repress -amylase. The results indicate that neither tagatose nor psicose repress -amylase induction (Fig. (Fig.77 D). The rapid metabolization of Suc into its constituent hexoses hampers easy approaches to Suc sensing. The same applies to hexose sensing, since most plant tissues can readily synthesize Suc when fed with hexoses. An exception to this rule is given in the experiments dealing with the effect of Suc on genes whose expression is not affected by hexoses. Suc sensing has been demonstrated for the modulation of the patatin promoter ( Wenzler et al., 1989 ; Jefferson et al., 1990 ), of the rolC promoter in transgenic tobacco ( Yokoyama et al., 1994 ), and of the proton-Suc symporter activity in sugar beet ( Chiou and Bush, 1998 ). Furthermore, Suc represses translation of a transcription factor in Arabidopsis ( Rook et al., 1998 ). In these experiments, the authors could separate the effects of Suc from those related to its metabolism into Glc and Fru, since the effect of these hexoses was either absent or less pronounced w Continue reading >>
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Disaccharides And Glycosidic Bonds
Monosaccharides such as glucose can be linked together in condensation reactions. For example, sucrose (table sugar) is formed from one molecule of glucose and one of fructose, as shown below. Molecules composed of two monosaccharides are called disaccharides. Click on the step numbers to see the steps in the formation of sucrose. Click on the mouse icon at left to clear the steps to see them again. First, two monosaccharides are brought together such that two hydroxyl groups are close to each other. Note that the glucose half of sucrose has the configuration at C1. Glycosidic bonds are labeled or depending on the anomeric configuration of the C1 involved in the glycosidic bond. Maltose, which links two glucose molecules, has an glycosidic bond like sucrose. Lactose, the primary sugar in milk, links glucose and galactose in a glycosidic bond instead. Can glycosidic bonds only be formed between C1 and C4, as in sucrose, maltose, and lactose? Glycosidic bonds can also be formed between other carbons of monosaccharides. For example, several polymers of glucose involve glycosidic bonds between C1 and C6 in addition to bonds between C1 and C4. This fact makes polymers of monosaccharides potentially much more complex than polymers of amino acids (proteins) or nucleotides (DNA), as you will see shortly. Continue reading >>
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Biochemistry/carbohydrates
"Carbohydrates" are chemically defined as "polyhydroxy aldehyde or polyhydroxy ketones or complex substances which on hydrolysis yield polyhydroxy aldehyde or polyhydroxy ketone." Carbohydrates are one of the fundamental classes of macromolecules found in biology. Carbohydrates are commonly found in most organisms, and play important roles in organism structure, and are a primary energy source for animals and plants. Most carbohydrates are sugars or composed mainly of sugars. By far, the most common carbohydrate found in nature is glucose, which plays a major role in cellular respiration and photosynthesis. Some carbohydrates are for structural purposes, such as cellulose (which composes plants' cell walls) and chitin (a major component of insect exoskeletons). However, the majority of carbohydrates are used for energy purposes, especially in animals. Carbohydrates are made up of a 1:2:1 ratio of Carbon, Hydrogen, and Oxygen (CH2O)n These are used only for energy in living organisms. Simple carbohydrates are also known as "Monosaccharides".The chemical formula for all the monosaccharides is CnH2nOn. They are all structural isomers of each other. There are two main types of monosaccharides. The first type are aldoses, containing an aldehyde on the first carbon, and the second type are ketoses, which have a ketone on the second carbon (This carbonyl group is always located on the second carbon). Name Formula Aldoses Ketoses Trioses C3 H6 O3 Glycerose Dihydroxyacetone Tetroses C4 H8 O4 Erythrose Erythrulose Pentoses C5 H10 O5 Ribose Ribulose Hexoses C6 H12 O6 Glucose Fructose Heptose C7 H14 O7 Glucoheptose Sodoheptulose The suffix -oses is kept for the aldoses & the suffix -uloses is kept for the ketoses. Except fructose ketoses are as common as aldoses.The most abundant m Continue reading >>
Is Glucose A Disaccharide? If So, Why?
Answer Wiki Types and origin of carbohydrates There are four families of carbohydrates: monosaccharides, disaccharides, oligosaccharides and polysaccharides. Each family is distinguished by the number of simple sugar molecules that the compounds. monosaccharides The monosaccharide molecule represents the carbohydrate base unit. There are more than 200 in the wild. They differ between them by the number of carbon atoms in the composition of the molecule. mettants in a called the original prefix greek representing the number of carbon atoms of the cycle, followed by the suffix "venture" qu'ils'agit indicating a sugar. For example, monosaccharides to 3 carbon atoms are called trioses, tetroses 4 carbons, 5-carbon pentose, hexose carbons 6 and 7 carbons the heptoses. The most important monosaccharides diet are: glucose, fructose and galactose. Glucose, also called dextrose or blood sugar, occurs naturally in foods, but it can also come from the digestion of complex carbohydrates. The body can also synthesize glucose through gluconeogenesis, a mechanism which synthesizes glucose from non-carbohydrate carbon skeletons of compounds such as glycerol, pyruvate, lactate, or certain amino acids. Gluconeogenesis occurs primarily in the liver. Glucose is absorbed directly through the small intestine without digestion (without intervention of digestive enzymes). Once in the blood, glucose can: either be used directly by cells to produce energy, and it is the case that if the organization has an immediate need for energy. either be stored as glycogen in the muscles and liver, and it is the case that when the body is to reduce the glycogen reserves during physical effort, for example, either be turned into fat to be stored in fat cells, liver or mammary glands as reserve fat. More gluc Continue reading >>
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Disaccharides
Disaccharides are formed by the condensation reactions of two simple sugar molecules. Condensation is the loss of water in a chemical reaction. Two OH groups, one from each sugar molecule, come together to release water and form an oxygen bridge between. One of the OH groups is attached to the anomeric carbon (the carbon that has 2 oxygens bonded to it). Here you see the formation of sucrose from the 6-membered form of glucose and the 5-membered form of fructose. Note that linear fructose has a ketone rather than an aldehyde group. Which carbon in glucose and in fructose would be the carbonyl carbon in the linear form? Another example is the condensation of 2 molecules of glucose. Sucrose is the disaccharide of glucose and fructose.This is common table sugar and it comes from sugar cane and sugar beets. Maple syrup also contains sucrose. Maltose is derived from the coupling of two molecules of glucose.It is produced when the enzyme amylase breaks down starch. Maltose is formed in germinating cereal grains and is important in the production of alcohol by fermentation. This is a disaccharide of galactose and glucose.Lactose is also called milk sugar and it makes up between 2 and 8 % of milk. Most reactions involve the combination of an electrophile and a nucleophile. Remember that a strongly electrophilic carbon is formed by the protonation of a simple sugar. The cation on carbon is stabilized by the adjacent oxygen atom. The empty p orbital on carbon can overlap with the filled p orbital on oxygen. The carbon is still electron-poor though and will react rapidly with nucleophiles. Most reactions can be viewed as the addition of a nucleophile to an electrophile. In acid-base reactions, the base is also a nucleophile and combines with the proton, an electrophile. When carb Continue reading >>
Carbohydrates
Carbohydrates (also called saccharides) are molecular compounds made from just three elements: carbon, hydrogen and oxygen. Monosaccharides (e.g. glucose) and disaccharides (e.g. sucrose) are relatively small molecules. They are often called sugars. Other carbohydrate molecules are very large (polysaccharides such as starch and cellulose). Carbohydrates are: a source of energy for the body e.g. glucose and a store of energy, e.g. starch in plants building blocks for polysaccharides (giant carbohydrates), e.g. cellulose in plants and glycogen in the human body components of other molecules eg DNA, RNA, glycolipids, glycoproteins, ATP Monosaccharides Monosaccharides are the simplest carbohydrates and are often called single sugars. They are the building blocks from which all bigger carbohydrates are made. Monosaccharides have the general molecular formula (CH2O)n, where n can be 3, 5 or 6. They can be classified according to the number of carbon atoms in a molecule: n = 3 trioses, e.g. glyceraldehyde n = 5 pentoses, e.g. ribose and deoxyribose ('pent' indicates 5) n = 6 hexoses, e.g. fructose, glucose and galactose ('hex' indicates 6) There is more than one molecule with the molecular formula C5H10O5 and more than one with the molecular formula C6H12O6. Molecules that have the same molecular formula but different structural formulae are called structural isomers. Glyceraldehyde's molecular formula is C3H6O3. Its structural formula shows it contains an aldehyde group (-CHO) and two hydroxyl groups (-OH). The presence of an aldehyde group means that glyceraldehyde can also be classified as an aldose. It is a reducing sugar and gives a positive test with Benedict's reagent. CH2OHCH(OH)CHO is oxidised by Benedict's reagent to CH2OHCH(OH)COOH; the aldehyde group is oxidised to Continue reading >>
Disaccharide - An Overview | Sciencedirect Topics
Fuming Zhanga, ... Robert J. Linhardtabc, in Handbook of Glycomics , 2010 Disaccharide analysis is one of the most important ways to characterize a GAG, which consists of repeating disaccharide units composed of different monosaccharide residues, linkages, and sulfation patterns. Disaccharide analysis typically follows the complete enzymatic digestion of GAGs by corresponding lyases. There are several techniques used to measure the resulting disaccharide composition. Capillary electrophoresis (CE) is often used in disaccharide analysis because of its high resolving power and sensitivity. The methods for CE disaccharide analysis are presented in Table 3.3 [5376]. CE can be used with UV, fluorescence, or MS for detection of analyte. Strong ion-exchange (SAX) high-performance liquid chromatography (HPLC) has also been used for disaccharide analysis [77,78]. This method is also widely used in oligosaccharide mapping. SAX-HPLC relies on UV detection at 232nm and thus has rather low sensitivity, limiting its utility for microanalysis of GAGs prepared from small tissue of cell culture samples. Reversed phase (RP)-HPLC is another method to analyze disaccharide composition. This method often utilizes fluorescence derivatization of the disaccharides with 2-aminoacridone or some other fluorescent tag [79]. RP-HPLC has been used for the disaccharide analysis of both HS and CS/DS obtained from biological samples. The pre-analysis derivatization of disaccharides, without sample clean-up, is followed by RP-HPLC separation and can detect as little as approximately 100pg (approximately 1013mol) of each disaccharide present in the mixture, thereby requiring >10ng of total GAG for analysis. Reversed-phase ion-pairing (RPIP)-HPLC is also widely used recently to analyze disaccharide compos Continue reading >>
Disaccharide | Biochemistry | Britannica.com
Disaccharide, also called double sugar, any substance that is composed of two molecules of simple sugars ( monosaccharides ) linked to each other. Disaccharides are crystalline water-soluble compounds . The monosaccharides within them are linked by a glycosidic bond (or glycosidic linkage), the position of which may be designated - or - or a combination of the two (-,-). Glycosidic bonds are cleaved by enzymes known as glycosidases. The three major disaccharides are sucrose , lactose , and maltose. In the bacterium Escherichia coli, energy is derived from the metabolism of disaccharide and oligosaccharide sugars and other small molecules. Sucrose, which is formed following photosynthesis in green plants, consists of one molecule of glucose and one of fructose bonded via an -,-linkage. Lactose (milk sugar), found in the milk of all mammals , consists of glucose and galactose connected by a -linkage. Maltose , a product of the breakdown of starches during digestion, consists of two molecules of glucose connected via an -linkage. Another important disaccharide, trehalose , which is found in single-celled organisms and in many insects , also consists of two molecules of glucose and an -linkage, but the linkage is distinct from the one found in maltose. Continue reading >>
