A carbohydrate is a biological molecule consisting of carbon (C), hydrogen (H) and oxygen (O) atoms, usually with a hydrogen:oxygen atom ratio of 2:1 (as in water); in other words, with the empirical formula Cm(H2O)n (where m could be different from n).[1] Some exceptions exist; for example, deoxyribose, a sugar component of DNA,[2] has the empirical formula C5H10O4.[3] Carbohydrates are technically hydrates of carbon;[4] structurally it is more accurate to view them as polyhydroxy aldehydes and ketones.[5]The term is most common in biochemistry, where it is a synonym of saccharide, a group that includes sugars, starch, and cellulose. The saccharides are divided into four chemical groups: monosaccharides, disaccharides, oligosaccharides, and polysaccharides. In general, the monosaccharides and disaccharides, which are smaller (lower molecular weight) carbohydrates, are commonly referred to as sugars.[6] The word saccharide comes from the Greek word (skkharon), meaning "sugar." While the scientific nomenclature of carbohydrates is complex, the names of the monosaccharides and disaccharides very often end in the suffix -ose. For example, grape sugar is the monosaccharide glucose, cane sugar is the disaccharide sucrose and milk sugar is the disaccharide lactose (see illustration).Carbohydrates perform numerous roles in living organisms. Polysaccharides serve for the storage of energy (e.g., starch and glycogen) and as structural components (e.g., cellulose in plants and chitin in arthropods). 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 include many other important biomolecules that play key roles in the immune system, fertilization, preventing pathogenesis, blood clotting, and development.[7]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, jams, and desserts).CarbohydratesCarbohydrates 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. SugarsMonosaccharidesThree common sugars share the same molecular formula: C6H12O6. 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. DisaccharidesThree common disaccharides: sucrose common table sugar = glucose + fructose lactose major sugar in milk = glucose + galactose maltose product of starch digestion = glucose + glucoseAlthough 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 disaccharides is C12H22O11 = 2 C6H12O6 H2O All sugars are very soluble in water because of their many hydroxyl groups. Although not as concentrated a fuel as fats, sugars are the most important source of energy for many cells. Carbohydrates provide the bulk of the calories (4 kcal/gram) in most diets, and starches provide the bulk of that. Starches are polysaccharides. PolysaccharidesStarchesStarches are polymers of glucose. Two types are found: amylose consists of linear, unbranched chains of several hundred glucose residues (units). The glucose residues are linked by a glycosidic bond between their #1 and #4 carbon atoms. amylopectin differs from amylose in being highly branched. At approximately every thirtieth residue along the chain, a short side chain is attached by a glycosidic bond to the #6 carbon atom (the carbon above the ring). The total number of glucose residues in a molecule of amylopectin is several thousand.Starches are insoluble in water and thus can serve as storage depots of glucose. Plants convert excess glucose into starch for storage. The image shows starch grains (lightly stained with iodine) in the cells of the white potato. Rice, wheat, and corn (maize) are also major sources of starch in the human diet.

Before starches can enter (or leave) cells, they must be digested. The hydrolysis of starch is done by amylases. With the aid of an amylase (such as pancreatic amylase), water molecules enter at the 1 -> 4 linkages, breaking the chain and eventually producing a mixture of glucose and maltose. A different amylase is needed to break the 1 -> 6 bonds of amylopectin. GlycogenAnimals store excess glucose by polymerizing it to form glycogen. The structure of glycogen is similar to that of amylopectin, although the branches in glycogen tend to be shorter and more frequent.Glycogen is broken back down into glucose when energy is needed (a process called glycogenolysis). In glycogenolysis, Phosphate groups not water break the 1 -> 4 linkages The phosphate group must then be removed so that glucose can leave the cell. The liver and skeletal muscle are major depots of glycogen. There is some evidence that intense exercise and a high-carbohydrate diet ("carbo-loading") can increase the reserves of glycogen in the muscles and thus may help marathoners work their muscles somewhat longer and harder than otherwise. But for most of us, carbo loading leads to increased deposits of fat. CelluloseCellulose is probably the single most abundant organic molecule in the biosphere. It is the major structural material of which plants are made. Wood is largely cellulose while cotton and paper are almost pure cellulose. Like starch, cellulose is a polysaccharide with glucose as its monomer. However, cellulose differs profoundly from starch in its properties. Because of the orientation of the glycosidic bonds linking the glucose residues, the rings of glucose are arranged in a flip-flop manner. This produces a long, straight, rigid molecule. There are no side chains in cellulose as there are in starch. The absence of side chains allows these linear molecules to lie close together. Because of the many -OH groups, as well as the oxygen atom in the ring, there are many opportunities for hydrogen bonds to form between adjacent chains.The result is a series of stiff, elongated fibrils the perfect material for building the cell walls of plants. This electron micrograph (courtesy of R. D. Preston) shows the cellulose fibrils in the cell wall of a green alga. These long, rigid fibrils are a clear reflection of the nature of the cellulose molecules of which they are composed. Carbohydrate Classification There are a variety of interrelated classification schemes. The most useful classification scheme divides the carbohydrates into groups according to the number of individual simple sugar units. Monosaccharides contain a single unit; disaccharides contain two sugar units; and polysaccharides contain many sugar units as in polymers - most contain glucose as the monosaccharide unit.Carbohydrates

MonosaccharidesDisaccharidesPolysaccharides

GlucoseSucroseStarch

GalactoseMaltoseGlycogen

FructoseLactoseCellulose

Ribose

Glyceraldehyde

Number of CarbonsMonosaccharides can be further classified by the number of carbons present. Hexoses (6-carbons) are by far the most prevalent.Number of Carbons

Six = HexoseFive = PentoseThree = Triose

GlucoseRiboseGlyceraldehyde

Galactose

Fructose

Functional Groups Aldoses contain the aldehyde group - Monosaccharides in this group are glucose, galactose, ribose, and glyceraldehyde. Ketoses contain the ketone group - The major sugar in this group is fructose. Reducing: Contain a hemiacetal or hemiketal group. Sugars include, glucose, galactose, fructose, maltose, lactose Non-reducing: Contain no hemiacetal groups. Sucrose and all polysaccharides are in this group.Types of CarbohydratesBack to Top

Like all other biomolecules carbohydrates are made of micromolecules and macromolecules. Micromolecules are the monosaccharides while the macromolecules are the oligosaccharides and polysaccahrides. Actually, the micromolecules polymerize and condense to form macromolecules.

Carbohydrates basically are of three types - Monosaccharides, Oligosaccharides and Polysaccharides.

Monosaccharides or simple sugars consists of single polyhydroxy aldehyde or ketone. Most common classes of monosaccharides areAldoses -Aldotiroses, aldotertoses, aldopentoses, aldohextoses and aldoheptoses.Ketoses - Ketotrioses, ketotetroses, ketopentoses, ketohextoses, and ketoheptoses.

Oligosaccharides are polymerized monosaccharides, which contain more two to ten residues on hydrolysis.Oligosacharides are classified asdisaccharides, trisaccharides and tetrasaccharides.

Disaccahrides yield two monosaccharides on hydrolysis.Disaccharides are of two types - Reducing disaccharides (example maltose)and non-reducing disaccharides(example sucrose).Trisaccahrides are found in sugar beet and and cotton seed. Example raffinose.Tetrasaccharide yield four monosaccharides on hydrolysis. Example: stachyose.

Polysaccharides are polymeric anhyderides of monosaccharides. Polysaccharides are of two types based on their function and composition.Based on function, polysaccharides of two types storage and structural.Storage polysaccharides - starch.Structural polysaccharide - cellulose.

Based on composition polysaccharides are of two types homoplysaccharides and heteropolysaccharides. Homopolysaccharides give single type of monosaccharide on hydrolysis. Example Inulinpolymerof fructose.Heteropolysaccharides example hyaluronic acid, chondroitin sulphate.Example of CarbohydratesBack to Top

Following are common examples of carbohydrates:Monosaccharides - Glucose, galactose, glycerose, erythrose, ribose, ribulose, fructose.Oligosaccharides - Maltose, lactose, sucrose, raffinose, stachyose.Polysaccharides - Starch, glycogen, cellulose, pectin, inulin,hyaluonic acid.

Foods rich in carbohydrates are referred to as strachy foods. They are found in legumes, starchy vegetables, whole-grain breads and cereals. They also occur naturally with vitamins and minerals in foods like milk, fruits, milk products. They are alsdo found in refined and processedproducts like candy, carbonated beverages, and table sugar.Carbohydrates ClassificationBack to Top

Carbohydrates are classified into three groups

Monosaccharides or MonosachorosesFrom Greek, mono=one; sakchron=sugar.

Monosaccharides are often called simple sugars, these are compound which possess a free aldehyde or ketone group. They are the simplest sugars and cannot be hydrolyzed. The general formula is Cn(H2O)n or CnH2nOn. The monosaccharides are subdivided into tiroses, tertrose, pentoses, hexoses, heptoses etc., and also as aldoses or ketoses depending upon whether they contian aldehyde or ketone group.

Examples of monosaccharides are Fructose, Erythrulose, Ribulose.

Oligosaccharides or Oligosaccharoses In Greek, Oligo means few.Oligosaccharides are compound sugars that yield 2 to 10 molecules of the same or different monosaccharides on hydrolysis.Oligosaccharides yielding 2 molecules of monosaccharides on hydrolysis is known as a disaccharide, and the ones yielding 3 or 4 monosaccharides are known as trisaccharides and tetrasaccharides respectively and so on. The general formula of disaccharides is Cn(H2O)n-1 and that of trisaccharides is Cn(H2O)n-2 and so on.

Example of disaccharides are sucrose, lactose, maltose etc.Trisaccharides are Raffinose, Rabinose.

Polysaccharides or PolysaccharosesIn Greek, poly means many.Polysaccharides arecompound sugarsand yield more than 10 molecules of monosaccharides on hydrolysis. Theya re further classified depending on they type of molecules produced as aresullt of hydrolysis. Theymay be homopolysaccharides i.e, monosaccharides of thesame type or heteropolysaccharides i.e., monosaccharides of different types. The general formula is(C6H10O5)x.

Example of homopolysaccharides are starch, glycogen, cellulose, pectin.Heteropolysaccharides areHyaluronic acid, Chondrotin.

Monosaccharides (from Greek monos: single, sacchar: sugar; British English: monosaccharaides) are the most basic units of carbohydrates. They are the simplest form of sugar and are usually colorless, water-soluble, crystalline solids. Some monosaccharides have a sweet taste. Examples of monosaccharides include glucose (dextrose), fructose (levulose) and galactose. Monosaccharides are the building blocks of disaccharides (such as sucrose and lactose) and polysaccharides (such as cellulose and starch). Further, each carbon atom that supports a hydroxyl group (so, all of the carbons except for the primary and terminal carbon) is chiral, giving rise to a number of isomeric forms, all with the same chemical formula. For instance, galactose and glucose are both aldohexoses, but have different physical structures and chemical properties.[1]Glucose, a monosaccharide (or simple sugar) also known as grape sugar or corn sugar, is an important carbohydrate in biology.The living cell uses it as a source of energy and metabolic intermediate.Glucose is one of the main products of photosynthesis and starts cellular respiration in both prokaryotes and eukaryotes.

All major dietary carbohydrates contain glucose,either as their only building block,as in starch and glycogen,or together with another monosaccharide, as in sucrose and lactose.In the lumen of the duodenum and small intestine the oligo- and polysaccharides are broken down to monosaccharides by the pancreatic and intestinal glycosidases.Glucose is then transported across the apical membrane of the enterocytes by SLC5A1,and later across their basal membrane by SLC2A2.Some of the glucose goes directly toward fueling brain cells and erythrocytes,while the rest makes its way to the liver and muscles,where it is stored as glycogen,and to fat cells,where it can be used to power reactions which synthesize some fats.Glycogen is the body's auxiliary energy source,tapped and converted back into glucose when there is need for energy.

Properties:

The Gibbs free energy of formation of solid glucose is -909 kJ/mol and the enthalpy of formation is -1007 kJ/mol.The heat of combustion (with liquid water in the product) is about 2803 kJ/mol, or 3.72 kcal per gram.The G (change of Gibbs free energy) for this combustion is about -2880 kJ/mol.

Upon heating, glucose,like any carbohydrate,will undergo pyrolysis (carbonization) yielding steam and a char consisting mostly of carbon.This reaction is exothermic, releasing about 0.237 kcal per gram.Monosaccharides are important in several ways. A constant source of blood glucose is compulsory for human life. Glucose is the preferred energy source of the brain. Polysaccharides function as storage and structural components in plants and animals.MonosaccharidesA monosaccharide is a carbohydrate that can't be hydrolyzed to simpler carbohydrate units. The monosaccharide is the basic carbohydrate unit of cellular metabolism.Monosaccharides are single sugar units. Their general formula is (CH2O)n. They are classified according to the number of carbon atoms as trioses (3C), tetroses (4C), pentoses (5C), hexoses (6C) and heptoses (7C). Of these, pentoses and especially hexoses (e.g. glucose, fructose, galactose) are the most common so we will concentrate on them.The hexose monosaccharides are the most important carbohydrate sources of cellular energy. 3 hexoses glucose, galactose, and fructose are of major significance in nitrition. All 3 have the same molecular formula and thus contain an equal no. of reduced carbons. They differ in structure but are biologically interconvertible. Glucose plays a cenral role in carbohydrate energy utilization. Other carbohydartes are usually converted to glucose before cellular utilization.1.GlucoseGlucose is the most important of the monosaccharides. It is an aldohexose and is found in the free state in plant and animal tissue.FunctionGlucose is commonly known as dextrose or grape sugar. It is a component of the disaccharides sucrose, maltose, and lactose, and is also the monomer of the polysaccharides starch, cellulose and glycogen. Among the common sugars, glucose is of intermediate sweetness.It is the most common respiratory substrate & the most common monosaccharides. It is also the key sugar of the body and is carried by the bloodstream to all body parts. The concentration of glucose in the blood is normally 80-100 mg per 100ml of blood. Because glucose is the most abundant carbohydrate in the blood, it is also sometimes known as blood suar. Glucose requires no digestion and therefore may be given intravenously to patients who cannot take food by mouth. Glucose is found in the urine of those who have diabetes mellitus (sugar diabetes). The condition in which glucose is excreted in the urine is called glycosuria.MonosaccharidesA monosaccharide is a carbohydrate that can't be hydrolyzed to simpler carbohydrate units. The monosaccharide is the basic carbohydrate unit of cellular metabolism.Monosaccharides are single sugar units. Their general formula is (CH2O)n. They are classified according to the number of carbon atoms as trioses (3C), tetroses (4C), pentoses (5C), hexoses (6C) and heptoses (7C). Of these, pentoses and especially hexoses (e.g. glucose, fructose, galactose) are the most common so we will concentrate on them.The hexose monosaccharides are the most important carbohydrate sources of cellular energy. 3 hexoses glucose, galactose, and fructose are of major significance in nitrition. All 3 have the same molecular formula and thus contain an equal no. of reduced carbons. They differ in structure but are biologically interconvertible. Glucose plays a cenral role in carbohydrate energy utilization. Other carbohydartes are usually converted to glucose before cellular utilization.1.GlucoseGlucose is the most important of the monosaccharides. It is an aldohexose and is found in the free state in plant and animal tissue.Structure

Open chain and ring formsStructure of the open chain and a and b ring forms of glucose. The three forms exist in equilibrium in aqueous solution, with 0.02 % open chain, 36% a glucose and 64% b glucose.The above graph shows glucose as having either an open chain or ring structure. The open chain form can be straight, but because of the bong angles between carbon atoms it is possible for sugars with 5 and 6 carbon atoms to bend and form stable ring structures. In hexoses like glucose, the first carbon atom combines with the oxygen atom on carbon atom no. 5 to give a 6-membered ring. Oxygen is part of the ring and that 1 carbon atom, carbon atom no. 6, sticks up out of the ring. In pentoses, the 1st carbon atom joins with the oxygen atom on the 4th carbon atom to give a 5-membered ring.The ring structures of pentoses and hexoses are the usual forms, with only a small proportion of the molecules existing in the open chain form at any 1 time. The ring structure is the form used to make dissaccharides and poly saccharides.

Alpha and beta isomersThe graph has also showed that glucose can exist in 2 possible forms, known as the alpha and beta forms. The hydroxyl group on carbon 1 can project below the ring (glucose) or above the ring ( glucose). Molecules like this, which have the same chemical formula but with different structures are said to be the isomers of each other. At any given moment in a glucose solution, some of the molecules will be in the open chain form (0.02%) and some in the ring form. This is more stable and therefore more common. A glucose molecule can switch spontaneously from the open chain form to either of the2 ring forms and back again. Overall equilibrium is reached where the proportions of the different forms remain constant.As stated above, only the ring form can be used to make disaccharides and polysaccharides. Despite the relatively small difference in structure between and glucose, there are important consequences. glucose is used to make the polysaccharide starch and glucose the polysaccharide cellulose molecules which have very different properties.Any 2 monosaccharides that differ only in the configuration around a single carbon atom are called epimers. Thus D- and L-glyceraldehyde are epimers.The structure called D-glucose is so named because the H and OH on carbon 5 are in the same configuration as the H and OH on carbon 2 in D-glyceraldehyde. The configuration of the H and OH on carbon 5 in L-glucose corresponds to the H and OH on carbon 2 in L-glyceraldehyde.FunctionGlucose is commonly known as dextrose or grape sugar. It is a component of the disaccharides sucrose, maltose, and lactose, and is also the monomer of the polysaccharides starch, cellulose and glycogen. Among the common sugars, glucose is of intermediate sweetness.It is the most common respiratory substrate & the most common monosaccharides. It is also the key sugar of the body and is carried by the bloodstream to all body parts. The concentration of glucose in the blood is normally 80-100 mg per 100ml of blood. Because glucose is the most abundant carbohydrate in the blood, it is also sometimes known as blood suar. Glucose requires no digestion and therefore may be given intravenously to patients who cannot take food by mouth. Glucose is found in the urine of those who have diabetes mellitus (sugar diabetes). The condition in which glucose is excreted in the urine is called glycosuria.2.FructoseFructose, also known as levulose, is a ketohexose that occurs in fruit juices, honey, and (along with glucose) as a constituent of sucrose.StructureThe open chain form can be represented in a Fischer projection formula:

Like glucose and galatose, fructose exists in both cyclic and open chain forms. One common cyclic structure is a five membered furanose ring in the configuration:

FunctionFructose is the major constituent of the polysaccharide insulin, a starchlike substance present in many plants. It is the sweetest of all the sugars,being about twice as sweet as glucose. This accounts for the sweetness of honey. The enzyme invertase, present in bees, spl;its sucrose into glucose and fructose. Fructose is metabolized directly but is also readily converted to glucose in the liver.3.GalactoseGalactose is also an aldohexose and occurs, along with glucose, in lactose and in many oligo- and polysaccharides such as pectin, gums, and mucilages. Galactose is an isomer of glucose, differing only in the spatial arrangement of the H and OH groups around carbon 4.StructureGalatose, like glucose, is an aldohexose and differs structurally from glucose only in the configuration of the H and OH group on the 4th carbon:

Galatose, like glucose, also exists primarily in 2 cyclic pyranose forms that have hemiacetal structures and undergo mutarotation:FunctionGalactose is synthesized in the mammary glands to make the lactose of milk. It is also a constituent of glycolipids and glycoproteins in many cell membranes such as those in nervous tissue. Galactose is less than half as sweet as glucose.4.Chief function of monosaccharidesExamplesFunctions

Trioses Glyceraldehyde dihydroxyacetone intermediates in respiration (as in glycolysis) photosynthesis (in dark reactions) other branches of carbohydrate metabolism

Pentoses ribose deoxyribose ribulose synthesis of nucleic acids; ribose is a constituent of RNA, deoxyribose of DNA synthesis of some coenzymes synthesis of ATP requires ribose ribulose bisphosphate is the CO2 acceptor in photosynthesis and is made from the 5C sugar ribulose

Hexoses glucose fructose galactose source of energy when oxidized in respiration; glucose is the most common respiratory substrate and the most common monosaccharide synthesis of disaccharides; 2 monosaccharide units can link together to form a disaccharide synthesis of polysaccharides; gulcose is particularly important in this role

Carbohydrate Monosaccharides inShare 7 By Dr Ananya Mandal, MDCarbohydrates are large macromolecules made up of carbon (C), hydrogen (H) and oxygen (O) and have the general formula Cx(H2O)y.Carbohydrates can be classified according to the number of sugar units they contain, as follows: Monosaccharides consist of a single sugar. Examples include glucose and fructose. Depending on the number of carbon atoms, the carbohydrate may be a triose, tetrose, pentose or hexose. Disaccharides contain two sugar units Oligosaccharides contain 3 to 10 sugar units Polysaccharides contain more than 10 sugar units.MonosaccharidesThe general formula for a monosaccharide is (CH2O)n. Monosaccharides are the simplest form of carbohydrate, which means they cannot be hydrolyzed or broken down into smaller carbohydrates. Monosaccharides are important molecules that complex carbohydrates are broken down into, in order to generate energy. They are also essential for building nucleic acids.Monosaccharide classificationRelated Stories Dietary linoleic acid lowers risk of coronary heart disease Changes in cell metabolism slow growth of colorectal cancer Helsinn, Pharmacosmos sign license agreement for commercialization of Monofer in the USMonosaccharides can be classified in three main ways, according to:1. The number of carbon atoms Monosaccharides containing three carbon atoms are referred to as trioses, while those with four carbons are called tetroses and those with five are called pentoses etc.2. The location of the carbonyl group If the carbonyl group is an aldehyde, then the monosaccharide is an aldose whereas if the carbonyl group is a ketone, the monosaccharide is a ketose.3. The molecules stereochemistry or chiral handedness This refers to the configuration of the molecule, which may exist in different structural forms or isomers.The first two classification systems above are often combined and a monosaccharide may be called an aldohexose (e.g. glucose), an aldopentose (e.g. ribose) or a ketohexose (e.g. fructose), for example.Apart from the first and last carbon atom, each carbon atom bearing a hydroxyl group is asymmetric and may have two possible configurations in space (R or S). A number of isomers can therefore exist for any monosaccharide.GlucoseGlucose is a carbohydrate, and is the most important simple sugar in human metabolism. Glucose is called a simple sugar or a monosaccharide because it is one of the smallest units which has the characteristics of this class of carbohydrates. Glucose is also sometimes called dextrose. Corn syrup is primarily glucose. Glucose is one of the primary molecules which serve as energy sources for plants and animals. It is found in the sap of plants, and is found in the human bloodstream where it is referred to as "blood sugar". The normal concentration of glucose in the blood is about 0.1%, but it becomes much higher in persons suffering from diabetes.

When oxidized in the body in the process called metabolism, glucose produces carbon dioxide, water, and some nitrogen compounds and in the process provides energy which can be used by the cells. The energy yield is about 686 kilocalories (2870 kilojoules) per mole which can be used to do work or help keep the body warm. This energy figure is the change in Gibbs free energy G in the reaction, the measure of the maximum amount of work obtainable from the reaction. As a primary energy source in the body, it requires no digestion and is often provided intravenously to persons in hospitals as a nutrient. GlucoseGlucose is a carbohydrate, and is the most important simple sugar in human metabolism. Glucose is called a simple sugar or a monosaccharide because it is one of the smallest units which has the characteristics of this class of carbohydrates. Glucose is also sometimes called dextrose. Corn syrup is primarily glucose. Glucose is one of the primary molecules which serve as energy sources for plants and animals. It is found in the sap of plants, and is found in the human bloodstream where it is referred to as "blood sugar". The normal concentration of glucose in the blood is about 0.1%, but it becomes much higher in persons suffering from diabetes.

When oxidized in the body in the process called metabolism, glucose produces carbon dioxide, water, and some nitrogen compounds and in the process provides energy which can be used by the cells. The energy yield is about 686 kilocalories (2870 kilojoules) per mole which can be used to do work or help keep the body warm. This energy figure is the change in Gibbs free energy G in the reaction, the measure of the maximum amount of work obtainable from the reaction. As a primary energy source in the body, it requires no digestion and is often provided intravenously to persons in hospitals as a nutrient. A monosaccharide is one saccharide (or sugar) molecule. An example of a monosaccharide is glucose.A disaccharide is two saccharides (sugars) bonded together through a dehydration reaction. An example of a disaccharide is maltose which is two glucose linked together. A polysaccharide is typically ten or more saccharides bonded together. Cellulose is an example of a polysaccharide, which is ten or more glucose linked together.What is the difference between a monosaccharide and a disaccharide?A: The body requires less effort to break down monosaccharides, resulting in easier digestion and more energy for the body than disaccharides. Monosaccharides include fructose, glucose and galactose, while disaccharides include lactose, sucrose and maltose.Keep Learning What is the difference between monosaccharide and polysaccharide?

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Both disaccharides and monosaccharides are a form of carbohydrate called simple sugars. Monosaccharides contain one sugar and disaccharides contain two sugars, and for a disaccharide to form, two monosaccharides must come together via a covalent bond. Many sugars present in foods are disaccharides, and they also exist in nature in the sucrose contained in fruits and vegetables. Sucrose cannot be hydrolyzed (adding water to cleave chemical bonds) but other disaccharides can be.The simplest type of carbohydrate is the monosaccharide. Since they are the simplest form, further hydrolyzing is not possible. Monosaccharides work to reduce other sugars and they taste sweet. Due to their reducing abilities, they work in Fehling's or benedict's reagents to produce a positive result. They get their classification from whether they have a keto or aldehyde group and how many carbon atoms a molecule has. For example, if there are six carbon atoms on a monosaccharide, it is a hexose, and if there are five carbon atoms, it is a pentose.

Monosaccharides and disaccharides are the two kinds of simple sugars, a form of carbohydrate. In contrast to polysaccharides, which contain three or more sugars and are also known as complex carbohydrates, monosaccharides and disaccharides contain one and two sugars, respectively. Monosaccharides include glucose, fructose, and galactose. Disaccharides, by contrast, include sucrose, lactose, and maltose, and these are made up of two monosaccharides bonded together, such as glucose and fructose or even glucose with glucose. Monosaccharides require the least effort by the body to break down and therefore are digested and subsequently available for energy more quickly than disaccharides.Carbohydrates are the bodys most immediately available source of energy, the source it relies upon for everything from getting through a workout to fueling the brain. The more complex the carbohydrate that is, the more sugars it contains the longer it takes to be broken down in the intestines to its simplest components, monosaccharides and disaccharides. Glucose, a form of monosaccharide, is the bodys preferred energy source, and it is also known as blood sugar. Most carbohydrates, whether disaccharides or polysaccharides, end up in glucose form once broken down in the digestive tract. In other words, a major difference between monosaccharides and disaccharides is that monosaccharides are used immediately for energy, whereas disaccharides must be converted into their monosaccharide components before they are of use to the body.AdThe foods from which monosaccharides and disaccharides like fructose and sucrose are derived for commercial purposes is another difference between the two. Glucose is found in a large number of living organisms, from plants, to insects, to humans. In commercial food production, however, fructose tends to be the preferred sweetener, as it is sweeter than table sugar and can be made cheaply from corn. High fructose corn syrup, for instance, is a fructose sweetener derived from corn that is found in many sweet foods and beverages like baked goods and soda.Disaccharides are obtained from a variety of plant and animal sources, sources that naturally contain a combination of monosaccharides. Sucrose, the scientific name for table sugar, is a disaccharide that contains both glucose and fructose. It is typically derived from the sugar cane or sugar beet plants, both of which are vegetables. Lactose, another disaccharide, comes not from plants but from animals as it is the type of sugar found in milk and other dairy products. It is made up of glucose combined with galactose.DisaccharideFrom Wikipedia, the free encyclopediaA disaccharide or biose[1] is the carbohydrate formed when two monosaccharides undergo a condensation reaction which involves the elimination of a small molecule, such as water, from the functional groups only. Like monosaccharides, disaccharides form an aqueous solution when dissolved in water. Three common references are sucrose, lactose,[2] and maltose."Disaccharide" is one of the four chemical groupings of carbohydrates (monosaccharide, disaccharide, oligosaccharide, and polysaccharide).Contents 1 Classification 2 Formation 3 Properties 4 Common disaccharides 5 References 6 External linksClassificationThere are two different types of disaccharides: reducing disaccharides, in which one monosaccharide, the reducing sugar, still has a free hemiacetal unit; and non-reducing disaccharides, in which the components bond through an acetal linkage between their anomeric centers and neither monosaccharide has a free hemiacetal unit. Cellobiose and maltose are examples of reducing disaccharides. Sucrose and trehalose are examples of non-reducing disaccharides. [3] [4]FormationDisaccharides are formed when two monosaccharides are joined together and a molecule of water is removed, a process known as dehydration reaction. For example; milk sugar (lactose) is made from glucose and galactose whereas the sugar from sugar cane and sugar beets (sucrose) is made from glucose and fructose. Maltose, another notable disaccharide, is made up of two glucose molecules.[5] The two monosaccharides are bonded via a dehydration reaction (also called a condensation reaction or dehydration synthesis) that leads to the loss of a molecule of water and formation of a glycosidic bond.[6]PropertiesThe glycosidic bond can be formed between any hydroxyl group on the component monosaccharide. So, even if both component sugars are the same (e.g., glucose), different bond combinations (regiochemistry) and stereochemistry (alpha- or beta-) result in disaccharides that are diastereoisomers with different chemical and physical properties.Depending on the monosaccharide constituents, disaccharides are sometimes crystalline, sometimes water-soluble, and sometimes sweet-tasting and sticky-feeling.Common disaccharidesDisaccharideUnit 1Unit 2Bond

Sucrose (table sugar, cane sugar, beet sugar, or saccharose)GlucoseFructose(12)

LactuloseGalactoseFructose(14)

Lactose (milk sugar)GalactoseGlucose(14)

Maltose (malt sugar)GlucoseGlucose(14)

TrehaloseGlucoseGlucose(11)

CellobioseGlucoseGlucose(14)

ChitobioseGlucosamineGlucosamine(14)

Maltose, cellobiose, and chitobiose are hydrolysis products of the polysaccharides starch, cellulose, and chitin, respectively.Less common disaccharides include:[7]DisaccharideUnitsBond

Kojibiosetwo glucose monomers(12) [8]

Nigerosetwo glucose monomers(13)

Isomaltosetwo glucose monomers(16)

,-Trehalosetwo glucose monomers(11)

,-Trehalosetwo glucose monomers(11)[9]

Sophorosetwo glucose monomers(12)

Laminaribiosetwo glucose monomers(13)

Gentiobiosetwo glucose monomers(16)

Turanosea glucose monomer and a fructose monomer(13)

Maltulosea glucose monomer and a fructose monomer(14)

Palatinosea glucose monomer and a fructose monomer(16)

Gentiobiulosea glucose monomer and a fructose monomer(16)

Mannobiosetwo mannose monomerseither (12), (13), (14), or (16)

Melibiosea galactose monomer and a glucose monomer(16)

Melibiulosea galactose monomer and a fructose monomer(16)

Rutinosea rhamnose monomer and a glucose monomer(16)

Rutinulosea rhamnose monomer and a fructose monomer(16)

Xylobiosetwo xylopyranose monomers(14)

Name 3 DisaccharidesList of Disaccharides

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This is the chemical structure of lactose, a disaccharide found in milk. Calvero, Creative Commons License Updated September 15, 2014.Disaccharides are sugars or carbohydrates made by linking two monosaccharides. This is a list of some disaccharides, including the monosaccharides they are made from and foods containing them. Sucrose, maltose, and lactose are the most familiar disaccharides, but there are others.1. sucrose (saccharose)glucose + fructoseSucrose is table sugar. It is purified from sugar cane or sugar beets. 2. maltoseglucose + glucoseMaltose is a sugar found in some cereals and candies. It is a product of starch digestions and may be purified from barley and other grains. 3. lactosegalactose + glucoseSugar found in milk. 4. lactulosegalactose + fructose 5. trehaloseglucose + glucose 6. cellobioseglucose + glucoseHydrolysis product of cellulose. AdsDownload Full Free Bookswww.readingfanatic.comDownload 1000's of Free eBooks, Get Reviews & More! Get AppBest chemistry educationchemistry.sciencedenmark.comLove the lab? Study chemistry at the University of CopenhagenScience Discovers God?y-jesus.comDo New Scientific Discoveries Point to a Creator of the Universe? Glucose Foods Chemistry Cellulose Blood Glucose Control CarbohydrateBonds and PropertiesNote multiple disaccharides are possible when monosaccharides bond to each other, since a glycosidic bond can form between any hydroxyl group on the component sugars. For example, two glucose molecules can join to form maltose, trehalose, or cellobiose. Even though these disaccharides are made from the same component sugars, they are distinct molcules with different chemical and physical properties from each other.

What are the different Polysaccharides?PrintEmailSaveImage Credit:http://bioweb.wku.edu/

Our body needs different types of food for the various functions, maintenance and growth. Food can be categorized broadly into carbohydrates, proteins and fats. While fats help in long term storage of energy which is not utilized right away, proteins help in building muscles and tissues. It is the carbohydrates that provide us with the energy required to do immediate work as they can be broken down right away into glucose which is utilized by the muscles to provide energy. These in turn are categorized into mono-saccharides(simple sugars), di-saccharides and polysaccharides. "SACCHARIDES" is derived from the greek word sacchar meaning "Sugar" and Poly meaning many sugars put together is basically a many sugared molecule in simple terms.Polysaccharidesare polymer carbohydrates made up of many monosaccharides or disaccharides. In simple terms, polysaccharides are complex sugar molecules made up of many blocks of simple sugar. The sugars are held together by the glycosidic bonds. A glycosidic bond is a covalent bond that joins a carbohydrate molecule to another group that may or may not be a carbohydrate. Their properties may vary from their building blocks i.e. the monosaccharides. Content What are the various types of Polysaccharides?What are the different kinds of Structural Polysaccharides?How are Polysaccharides processed in our Body?What is Dietary Fiber?What is Starch?What is Ganoderma Polysaccharide?What are the various types of Polysaccharides?If thepolysaccharideis made up of same type of monosaccharides, they are calledhomopolysaccharide or homoglycan, if it is mad up of different types of monosaccharides, they are known ashetero-polysaccharides or heteroglycans. The three common polysaccharides are Starch, Glycogen and Cellulose.Starches : While Starches are basically glucose polymers they need the enzyme Amylase to be broken down into glucose or to be digested. Plants store glucose in the form of starches.Glycogen : This is a storage form of glucose which is broken down into glucose when needed by animals and humans.Cellulose : These are polysaccharides that are the components of plants and are used as building material. They give both shape and structure to the plants. Cellulose cannot be digested by humans and that is the reason we cannot digest grass as it is made up of cellulose.Cows, horses, sheep, goats can digest cellulose because they have symbiotic bacteria in their intestinal tract and it is these bacteria with their enzymes that help in digesting cellulose. Humans still use Cellulose in the form of cotton, paper to make a lot of products which we are all too familiar with.What are the different kinds of Structural Polysaccharides?Chitin : It is a modified polysaccharides that contains Nitrogen. It is derived from glucose. It forms the external skeleton in many animals and is also bio-degradable. These polysaccharides resembles the cellulose in structure and the protein keratin in terms of function. This polysaccharide has a wide use in the agricultural, industrial and medical fields. Chitin has proven great use as a fertilizer and also to increase the immunity among the plants. It is used as a binder in dyes, adhesives and fabrics in the industrial area. It is also used as a surgical thread in the field of medicine because of its ability to dissolve.Pectin : This is a polysaccharide that forms the primary cell walls of many terrestrial plants. This is an example of heteropolysaccharides. It has various uses in the food industry as it acts as a gelling agent for jams and jellies. It is also used as a food thickening agent and stabilizer in juices, milk.Arabinoxylans : It is a polysaccharide found in the primary and secondary cell wall of plants i.e. wood and also in the cereal grains. It is a combination of arabinose and xylose.How are Polysaccharides processed in our Body?The food we eat is mixed with enzymes released by the body at various points to help in the digestion of the different types of molecules such as fats, proteins and carbohydrates. While chewing helps in breaking down the carbohydrates into smaller chunks, it is in the stomach followed by the small intestine that the final breakdown of the polysaccharides happens. The acid released in the stomach breaks them down into monosaccharides. The monosaccharides are glucose molecules which are the basic energy providing molecules. The glucose is further broken down in the cells into molecules of ATP - Adenosine Triphosphate. It is only when glucose is broken down into ATP can carbohydrates provide energy that can utilized by the body to do work. While the excess ATP molecules are converted by the liver into glycogen, these can be later broken down to glucose when needed by the body.What is Dietary Fiber?Dietary Fiber is a kind of polysaccharide that our body cannot digest. While women need at least 25 grams of fiber per day, men need anywhere from 30-38 grams per day. Dietary fiber is fiber that our body cannot digest to get any nutrients out of it and is the indigestable part that absorbs water as it moves down the alimentary canal and helps in bowel movement. But then not all fibers are dietary fibers. Some of the examples of fibers are,non-starch polysaccharides - cellulose, lignin, chitins and pectins, gum, mucilage. Both fibers and Dietary fibers are present in soluble and insoluble forms. Dietary fiber is only present in plant food which includes nuts, fruits and vegetables. Good sources of dietary fiber are broccoli, bran cereals, beans, peas, whole-wheat breads, grains and cereals. The soluble dietary fiber helps us in preventing constipation, reducing cholesterol levels, treatment of hemorrhoids and diverticulosis. The soluble fibers can be only digested with the help of the bacteria present in our digestive tract. The insoluble fiber is indigestible and helps in bowel movement.What is Starch?Starch, an example of the storage polysaccharide isproduced by all plants. It acts as a major energy reserve in plants and consists of glucose units. Starch is generally made up of 20-25%amylose and 75 to 80% amylopectin. Starch can be digested by hydrolysis with the help of "Amylases" enzymes. Amylases enzymes are present in animals and humans and hence starch can be digested by them. Rice, Potato, Maize and Wheat are all starches used by us as part of our diet. Starch is also used as an adhesive.What is Ganoderma Polysaccharide?Polysaccharides are present in a very high concentration in 2 Asian herbs, Ganoderma Lucidum and Cordyceps Sinensis. While the Ganoderma herb has Ganoderma Polysaccharides, the Cordyceps herb contains Cordyceps Polysaccharides. Both these herbs are proven to improve immune system, which helps in helping with cancer and diabetes.What are three examples of polysaccharides?Topic: Molecular Biology

cenicienta | (Level 1) Valedictorian Posted February 13, 2012 at 3:29 AM via webdislike 1 like What are three examples of polysaccharides?1 Answer | Add YoursTop Answer

belarafon | High School Teacher | (Level 2) Educator Emeritus Posted February 13, 2012 at 4:21 AM (Answer #1) dislike 1 like Privacy Policy | Send FeedbackPolysaccharides form when monosaccharides or disaccharides attach in chains. They are carbohydrate structures and generally heterogeneous. They are common in plants and are used as food and energy storage by most animals.The most prominent example of apolysaccharide is Starch, which is composed of glucose. While it is not soluble in water, it can be digested by any animal with the specific enzyme amylase, including humans. Starch helps regulate and store energy.Another commonpolysaccharide is Cellulose, the primary component of plants and especially trees. Since cellulose has a very strong molecular structure, it is not easily digested by animals; dietary fibers such as psylliumhusk are examples of cellulose.Chitin is another example; it is the smooth substance that forms crustacean and clam shells, as well as insect exoskeletons. Chitin is not easily broken down and is very common, and so acts as protection in organisms and has many industrial uses.PolysaccharideFrom Wikipedia, the free encyclopedia

3D structure of cellulose, a beta-glucan polysaccharide.

Amylose is a linear polymer of glucose mainly linked with (14) bonds. It can be made of several thousands of glucose units. It is one of the two components of starch, the other being amylopectin.Polysaccharides are polymeric carbohydrate molecules composed of long chains of monosaccharide units bound together by glycosidic linkages and on hydrolysis give the constituent monosaccharides or oligosaccharides. They range in structure from linear to highly branched. Examples include storage polysaccharides such as starch and glycogen, and structural polysaccharides such as cellulose and chitin.Polysaccharides are often quite heterogeneous, containing slight modifications of the repeating unit. Depending on the structure, these macromolecules can have distinct properties from their monosaccharide building blocks. They may be amorphous or even insoluble in water.[1][2] When all the monosaccharides in a polysaccharide are the same type, the polysaccharide is called a homopolysaccharide or homoglycan, but when more than one type of monosaccharide is present they are called heteropolysaccharides or heteroglycans.[3][4]Natural saccharides are generally of simple carbohydrates called monosaccharides with general formula (CH2O)n where n is three or more. Examples of monosaccharides are glucose, fructose, and glyceraldehyde[5] Polysaccharides, meanwhile, have a general formula of Cx(H2O)y where x is usually a large number between 200 and 2500. Considering that the repeating units in the polymer backbone are often six-carbon monosaccharides, the general formula can also be represented as (C6H10O5)n where 40n3000.Polysaccharides contain more than ten monosaccharide units. Definitions of how large a carbohydrate must be to fall into the categories polysaccharides or oligosaccharides vary according to personal opinion. Polysaccharides are an important class of biological polymers. Their function in living organisms is usually either structure- or storage-related. Starch (a polymer of glucose) is used as a storage polysaccharide in plants, being found in the form of both amylose and the branched amylopectin. In animals, the structurally similar glucose polymer is the more densely branched glycogen, sometimes called 'animal starch'. Glycogen's properties allow it to be metabolized more quickly, which suits the active lives of moving animals.Cellulose and chitin are examples of structural polysaccharides. Cellulose is used in the cell walls of plants and other organisms, and is said to be the most abundant organic molecule on earth.[6] It has many uses such as a significant role in the paper and textile industries, and is used as a feedstock for the production of rayon (via the viscose process), cellulose acetate, celluloid, and nitrocellulose. Chitin has a similar structure, but has nitrogen-containing side branches, increasing its strength. It is found in arthropod exoskeletons and in the cell walls of some fungi. It also has multiple uses, including surgical threads. Polysaccharides also include callose or laminarin, chrysolaminarin, xylan, arabinoxylan, mannan, fucoidan and galactomannan.Contents 1 Function 1.1 Structure 2 Storage polysaccharides 2.1 Starches 2.2 Glycogen 3 Structural polysaccharides 3.1 Arabinoxylans 3.2 Cellulose 3.3 Chitin 3.4 Pectins 4 Acidic polysaccharides 5 Bacterial capsular polysaccharides 6 Chemical identification tests for polysaccharides 6.1 Periodic acid-Schiff stain (PAS) 7 See also 8 References 9 External linksFunctionStructureNutrition polysaccharides are common sources of energy. Many organisms can easily break down starches into glucose; however, most organisms cannot metabolize cellulose or other polysaccharides like chitin and arabinoxylans. These carbohydrate types can be metabolized by some bacteria and protists. Ruminants and termites, for example, use microorganisms to process cellulose.Even though these complex to carbohydrates are not very digestible, they provide important dietary elements for humans. Called dietary fiber, these carbohydrates enhance digestion among other benefits. The main action of dietary fiber is to change the nature of the contents of the gastrointestinal tract, and to change how other nutrients and chemicals are absorbed.[7][8] Soluble fiber binds to bile acids in the small intestine, making them less likely to enter the body; this in turn lowers cholesterol levels in the blood.[9] Soluble fiber also attenuates the absorption of sugar, reduces sugar response after eating, normalizes blood lipid levels and, once fermented in the colon, produces short-chain fatty acids as byproducts with wide-ranging physiological activities (discussion below). Although insoluble fiber is associated with reduced diabetes risk, the mechanism by which this occurs is unknown.[10]Not yet formally proposed as an essential macronutrient (as of 2005), dietary fiber is nevertheless regarded as important for the diet, with regulatory authorities in many developed countries recommending increases in fiber intake.[7][8][11][12]Storage polysaccharidesStarchesStarches are glucose polymers in which glucopyranose units are bonded by alpha-linkages. It is made up of a mixture of amylose (1520%) and amylopectin (8085%). Amylose consists of a linear chain of several hundred glucose molecules and Amylopectin is a branched molecule made of several thousand glucose units (every chain of 2430 glucose units is one unit of Amylopectin). Starches are insoluble in water. They can be digested which can break the alpha-linkages (glycosidic bonds). Both humans and animals have amylases, so they can digest starches. Potato, rice, wheat, and maize are major sources of starch in the human diet. The formations of starches are the ways that plants store glucoseGlycogenGlycogen serves as the secondary long-term energy storage in animal and fungal cells, with the primary energy stores being held in adipose tissue. Glycogen is made primarily by the liver and the muscles, but can also be made by glycogenesis within the brain and stomach.[13]Glycogen is the analogue of starch, a glucose polymer in plants, and is sometimes referred to as animal starch,[14] having a similar structure to amylopectin but more extensively branched and compact than starch. Glycogen is a polymer of (14) glycosidic bonds linked, with (16)-linked branches. Glycogen is found in the form of granules in the cytosol/cytoplasm in many cell types, and plays an important role in the glucose cycle. Glycogen forms an energy reserve that can be quickly mobilized to meet a sudden need for glucose, but one that is less compact and more immediately available as an energy reserve than triglycerides (lipids).In the liver hepatocytes, glycogen can compose up to eight percent (100120g in an adult) of the fresh weight soon after a meal.[15] Only the glycogen stored in the liver can be made accessible to other organs. In the muscles, glycogen is found in a low concentration of one to two percent of the muscle mass. The amount of glycogen stored in the bodyespecially within the muscles, liver, and red blood cells[16][17][18]varies with physical activity, basal metabolic rate, and eating habits such as intermittent fasting. Small amounts of glycogen are found in the kidneys, and even smaller amounts in certain glial cells in the brain and white blood cells. The uterus also stores glycogen during pregnancy, to nourish the embryo.[15]Glycogen is composed of a branched chain of glucose residues. It is stored in liver and muscles. It is an energy reserve for animals. It is the chief form of carbohydrate stored in animal body. It is insoluble in water. It turns red when mixed with iodine. It also yields glucose on hydrolysis. Schematic 2-D cross-sectional view of glycogen. A core protein of glycogenin is surrounded by branches of glucose units. The entire globular granule may contain approximately 30,000 glucose units.[19] A view of the atomic structure of a single branched strand of glucose units in a glycogen molecule.Structural polysaccharidesArabinoxylansArabinoxylans are found in both the primary and secondary cell walls of plants and are the copolymers of two pentose sugars: arabinose and xylose.CelluloseThe structural component of plants are formed primarily from cellulose. Wood is largely cellulose and lignin, while paper and cotton are nearly pure cellulose. Cellulose is a polymer made with repeated glucose units bonded together by beta-linkages. Humans and many animals lack an enzyme to break the beta-linkages, so they do not digest cellulose. Certain animals such as termites can digest cellulose, because bacteria possessing the enzyme are present in their gut. Cellulose is insoluble in water. It does not change color when mixed with iodine. On hydrolysis, it yields glucose. It is the most abundant carbohydrate in nature.ChitinChitin is one of many naturally occurring polymers. It forms a structural component of many animals, such as exoskeletons. Over time it is bio-degradable in the natural environment. Its breakdown may be catalyzed by enzymes called chitinases, secreted by microorganisms such as bacteria and fungi, and produced by some plants. Some of these microorganisms have receptors to simple sugars from the decomposition of chitin. If chitin is detected, they then produce enzymes to digest it by cleaving the glycosidic bonds in order to convert it to simple sugars and ammonia.Chemically, chitin is closely related to chitosan (a more water-soluble derivative of chitin). It is also closely related to cellulose in that it is a long unbranched chain of glucose derivatives. Both materials contribute structure and strength, protecting the organism.PectinsPectins are a family of complex polysaccharides that contain 1,4-linked -D-galactosyluronic acid residues. They are present in most primary cell walls and in the non-woody parts of terrestrial plants.Acidic polysaccharidesAcidic polysaccharides are polysaccharides that contain carboxyl groups, phosphate groups and/or sulfuric ester groups.Bacterial capsular polysaccharidesPathogenic bacteria commonly produce a thick, mucous-like, layer of polysaccharide. This "capsule" cloaks antigenic proteins on the bacterial surface that would otherwise provoke an immune response and thereby lead to the destruction of the bacteria. Capsular polysaccharides are water soluble, commonly acidic, and have molecular weights on the order of 100-2000 kDa. They are linear and consist of regularly repeating subunits of one to six monosaccharides. There is enormous structural diversity; nearly two hundred different polysaccharides are produced by E. coli alone. Mixtures of capsular polysaccharides, either conjugated or native are used as vaccines.Bacteria and many other microbes, including fungi and algae, often secrete polysaccharides to help them adhere to surfaces and to prevent them from drying out. Humans have developed some of these polysaccharides into useful products, including xanthan gum, dextran, welan gum, gellan gum, diutan gum and pullulan.Most of these polysaccharides exhibit useful visco-elastic properties when dissolved in water at very low levels.[20] This makes various liquids used in everyday life, such as some foods, lotions, cleaners, and paints, viscous when stationary, but much more free-flowing when even slight shear is applied by stirring or shaking, pouring, wiping, or brushing. This property is named pseudoplasticity or shear thinning; the study of such matters is called rheology.Viscosity of Welan gum

Shear Rate (rpm)Viscosity (cP)

0.323330

0.516000

111000

25500

43250

52900

101700

20900

50520

100310

Aqueous solutions of the polysaccharide alone have a curious behavior when stirred: after stirring ceases, the solution initially continues to swirl due to momentum, then slows to a standstill due to viscosity and reverses direction briefly before stopping. This recoil is due to the elastic effect of the polysaccharide chains, previously stretched in solution, returning to their relaxed state.Cell-surface polysaccharides play diverse roles in bacterial ecology and physiology. They serve as a barrier between the cell wall and the environment, mediate host-pathogen interactions, and form structural components of biofilms. These polysaccharides are synthesized from nucleotide-activated precursors (called nucleotide sugars) and, in most cases, all the enzymes necessary for biosynthesis, assembly and transport of the completed polymer are encoded by genes organized in dedicated clusters within the genome of the organism. Lipopolysaccharide is one of the most important cell-surface polysaccharides, as it plays a key structural role in outer membrane integrity, as well as being an important mediator of host-pathogen interactions.The enzymes that make the A-band (homopolymeric) and B-band (heteropolymeric) O-antigens have been identified and the metabolic pathways defined.[21] The exopolysaccharide alginate is a linear copolymer of -1,4-linked D-mannuronic acid and L-guluronic acid residues, and is responsible for the mucoid phenotype of late-stage cystic fibrosis disease. The pel and psl loci are two recently discovered gene clusters that also encode exopolysaccharides found to be important for biofilm formation. Rhamnolipid is a biosurfactant whose production is tightly regulated at the transcriptional level, but the precise role that it plays in disease is not well understood at present. Protein glycosylation, particularly of pilin and flagellin, became a focus of research by several groups from about 2007, and has been shown to be important for adhesion and invasion during bacterial infection.[22]Chemical identification tests for polysaccharidesPeriodic acid-Schiff stain (PAS)This section does not cite any references or sources. Please help improve this section by adding citations to reliable sources. Unsourced material may be challenged and removed. (March 2013)

Polysaccharides with unprotected vicinal diols or amino sugars (i.e. some OH groups replaced with amine) give a positive Periodic acid-Schiff stain (PAS). The list of polysaccharides that stain with PAS is long. Although mucins of epithelial origins stain with PAS, mucins of connective tissue origin have so many acidic substitutions that they do not have enough glycol or amino-alcohol groups left to react with PAS.

carbohydratesgen formulasimplest carbohydrate (structural formula)classification of carbohydratesimportance of monosaccharide w/ structual fornuladifference between monosaccharidewhat are disaccharides (w/ examples)what are polysaccharides (w/ examples)