In chemistry, a glycosidic bond is a certain type of functional group that joins a carbohydrate (sugar) molecule to an alcohol, which may be another carbohydrate. Specifically, a glycosidic bond is formed between the hemiacetal group of a saccharide (or a molecule derived from a saccharide) and the hydroxyl group of some alcohol. A substance containing a glycosidic bond is a glycoside. Chemistry (from Greek χημεία khemeia[1] meaning alchemy) is the science of matter at the atomic to molecular scale, dealing primarily with collections of atoms, such as molecules, crystals, and metals. ... In organic chemistry, functional groups are specific groups of atoms within molecules, that are responsible for the characteristic chemical reactions of those molecules. ... Lactose is a disaccharide found in milk. ... Functional group of an alcohol molecule. ... A hemiacetal is a functional group or compound containing the function group in the form of: where R and R are any carbon backbones. ... an essential structural component of living cells and source of energy for animals; includes simple sugars with small molecules as well as macromolecular substances; are classified according to the number of monosaccharide groups they contain. ... Hydroxide is a functional group consisting of oxygen and hydrogen: -O−H It has a charge of 1-. The term hydroxyl group is used when the functional group -OH is counted as a substituent of an organic compound. ... A glycoside is a molecule where a sugar group is bonded through its anomeric carbon to a nonsugar group by either an oxygen or a nitrogen atom. ...

Glucose and ethanol combine to form ethyl glucoside and water.

Image File history File links Download high resolution version (1697x395, 7 KB) Summary Formation of ethyl glucoside from glucose and ethanol, showing the anomeric carbon and the resulting glycosidic bond. ... Glucose (Glc), a monosaccharide (or simple sugar), is the most important carbohydrate in biology. ... Ethanol, also known as ethyl alcohol or grain alcohol, is a flammable, colorless, mildly toxic chemical compound with a distinctive perfume-like odor, and is the alcohol found in alcoholic beverages. ... Ethyl is a two-carbon substituent in organic chemistry. ... A glucoside is a glycoside that is derived from glucose. ... Water is a tasteless, odourless substance that is essential to all known forms of life and is known as the universal solvent. ...

Chemistry

The hemiacetal group of carbohydrates (which contains the anomeric carbon) is reactive, and glycosidic bonds form readily in the presence of acid. This is a condensation reaction as one molecule of water is released. Glycosidic bonds are fairly stable; they can be broken chemically by strong aqueous acids. A hemiacetal is a functional group or compound containing the function group in the form of: where R and R are any carbon backbones. ... It has been suggested that this article or section be merged with Anomer. ... For other uses, see Acid (disambiguation). ... A condensation reaction (also known as a dehydration reaction or dehydration synthesis when water is lost) is a chemical reaction in which two molecules or moieties react and become covalently bonded to one another by the concurrent loss of a small molecule, often water, methanol, or a type of hydrogen... Water is a tasteless, odourless substance that is essential to all known forms of life and is known as the universal solvent. ... Water is a tasteless, odourless substance that is essential to all known forms of life and is known as the universal solvent. ...

A glycosidic functional group is an example of an acetal. An acetal is a functional group or molecule containing the functional group of a carbon bonded to two -OR groups. ...

Saccharides in aqueous solution can exist in linear (rare) or cyclic form (more common), and these forms readily interconvert. Only the cyclic forms have an anomeric carbon and can form a glycosidic bond; once the bond has formed, the saccharide unit can no longer attain the linear form.

Polysaccharides

A glycosidic bond can join two monosaccharide molecules to form a disaccharide, as for instance in the linkage of glucose and fructose to create sucrose. More complicated polysaccharides such as starch, glycogen, cellulose or chitin consist of numerous monosaccharide units joined by glycosidic bonds. Monosaccharides are the simplest form of carbohydrates. ... Sucrose, a common disaccharide A disaccharide is a sugar (a carbohydrate) composed of two monosaccharides. ... Glucose (Glc), a monosaccharide (or simple sugar), is the most important carbohydrate in biology. ... Fructose (or levulose) is a simple sugar (monosaccharide) found in many foods and is one of the three most important blood sugars along with glucose and galactose. ... Sucrose (common name: table sugar, also called saccharose) is a disaccharide (glucose + fructose) with the molecular formula C12H22O11. ... Polysaccharides (sometimes called glycans) are relatively complex carbohydrates. ... Starch(CAS# 9005-25-8) is a complex carbohydrate which is insoluble in water; it is used by plants as a way to store excess glucose. ... Electron micrograph of a section of a liver cell showing glycogen deposits as accumulations of electron dense particles (arrows). ... Cellulose as polymer of β-D-glucose Cellulose in 3D Cellulose (C6H10O5)n is a long-chain polymeric polysaccharide carbohydrate, of beta-glucose [1][2]. It forms the primary structural component of green plants. ... Structure of chitin molecule Chitin (IPA: ) is one of the main components in the cell walls of fungi, the exoskeletons of insects and other arthropods, and in some other animals. ...

While the cyclic structures of monosaccharide units are fairly rigid, the glycosidic bonds confer flexibility to polysaccharide molecules.

Glycosidic bonds join monosaccharides to form polysaccharides, just like peptide bonds join amino acids to form proteins. A peptide bond is a chemical bond formed between two molecules when the carboxyl group of one molecule reacts with the amino group of the other molecule, releasing a molecule of water (H2O). ... The general structure of an α-amino acid molecule, with the amine group on the left and the carboxyl group on the right. ... A representation of the 3D structure of myoglobin, showing coloured alpha helices. ...

S- and N- and O-glycosidic bonds

Adenosine, a component of RNA, results from the sugar ribose and adenine via the formation of an N-glycosidic bond (shown as the vertical line between the N and the sugar cycle)

In analogy, one also considers S-glycosidic bonds, where the anomeric carbon of a sugar is bound to some other group via a sulfur (rather than an oxygen) atom, and N-glycosidic bonds, where the anomeric carbon is bound to some other group via a nitrogen atom. The glycosidic bonds discussed earlier are often called O-glycosidic bonds to distinguish them from S- and N-glycosidic bonds. Substances containing N-glycosidic bonds are also known as glycosylamines; the term "N-glycoside" is considered a misnomer by IUPAC and is discouraged. Image File history File links Download high resolution version (1902x2067, 12 KB) Description: Chemical structure of Adenosine. ... Image File history File links Download high resolution version (1902x2067, 12 KB) Description: Chemical structure of Adenosine. ... The chemical structure of adenosine Adenosine is a nucleoside comprised of adenine attached to a ribose (ribofuranose) moiety via a β-N9-glycosidic bond. ... Ribonucleic acid (RNA) is a nucleic acid polymer consisting of nucleotide monomers. ... Ribose Ribose, primarily seen as D-ribose, is an aldopentose — a monosaccharide containing five carbon atoms, and including an aldehyde functional group. ... Adenine is one of the two purine nucleobases used in forming nucleotides of the nucleic acids DNA and RNA. In DNA, adenine binds to thymine via two hydrogen bonds to assist in stabilizing the nucleic acid structures. ... It has been suggested that this article or section be merged with Anomer. ... General Name, Symbol, Number sulfur, S, 16 Chemical series nonmetals Group, Period, Block 16, 3, p Appearance lemon yellow Atomic mass 32. ... General Name, Symbol, Number oxygen, O, 8 Chemical series Nonmetals, chalcogens Group, Period, Block 16, 2, p Appearance colorless (gas) very pale blue (liquid) Atomic mass 15. ... General Name, Symbol, Number nitrogen, N, 7 Chemical series nonmetals Group, Period, Block 15, 2, p Appearance colorless Atomic mass 14. ... Glycosylamine is a compound consisting of an amine with a glycosidic linkage to a carbohydrate. ... The International Union of Pure and Applied Chemistry (IUPAC) is an international non-governmental organization devoted to the advancement of chemistry. ...

α-, β-, 1,4 and 1,6 glycosidic bonds

In general, one distinguishes between α- and β-glycosidic bonds, depending on whether the original hydroxyl group of the participating anomeric carbon is in the α or β configuration. In the standard way of drawing sugars, an α-glycosidic bond of a D-sugar emanates below the plane of the sugar, and a β-glycosidic bond emanates above that plane. (The figure above shows methyl α-D-glucoside.) It has been suggested that this article or section be merged with Anomer. ...

In a 1,4-glycosidic bond a C1-O-C4 bond is made involving the C1 of one sugar molecule and C4 of the other; likewise a C1-0-C6 bond is called a 1,6-glycosidic bond.

Examples from biochemistry

Important examples in biochemistry include DNA (or RNA), where deoxyribose (or ribose) sugar units are joined to nucleobases via N-glycosidic bonds. The polysaccharides often used for energy storage were already mentioned above. Organisms also often form glycoproteins by attaching sugars to proteins via O- or N-glycosidic bonds in a process known as glycosylation. Animals (and pharmacists) often join substances to glucuronic acid via glycosidic bonds in order to increase their water solubility; this is known as glucuronidation. Many other glycosides have important physiological functions. Biochemistry is the study of the chemical processes and transformations in living organisms. ... The general structure of a section of DNA Deoxyribonucleic acid (DNA) is a nucleic acid that contains the genetic instructions for the biological development of a cellular form of life or a virus. ... Ribonucleic acid (RNA) is a nucleic acid polymer consisting of nucleotide monomers. ... Deoxyribose Deoxyribose, also known as D-Deoxyribose and 2-deoxyribose, is an aldopentose — a monosaccharide containing five carbon atoms, and including an aldehyde functional group. ... Ribose Ribose, primarily seen as D-ribose, is an aldopentose — a monosaccharide containing five carbon atoms, and including an aldehyde functional group. ... Adenine Guanine Thymine Cytosine ... A glycoprotein is a macromolecule composed of a protein and a carbohydrate (an oligosaccharide). ... A representation of the 3D structure of myoglobin, showing coloured alpha helices. ... Glycosylation is the process or result of addition of saccharides to proteins and lipids. ... The α-D form of glucuronic acid. ... It has been suggested that Solid solubility be merged into this article or section. ... Example of glucuronidation Glucuronidation of alcohols and acids Glucuronidation is a major inactivating pathway for a huge variety of exogenous and endogenous molecules, including drugs, polluants, bilirubin, androgens, estrogens, mineralocorticoids, glucocorticoids, fatty acid derivatives, retinoids and bile acids. ... A glycoside is a molecule where a sugar group is bonded through its anomeric carbon to a nonsugar group by either an oxygen or a nitrogen atom. ...

Enzymes

Enzymes that form or break glycosidic bonds (i.e. that catalyze their hydrolysis) are called glycoside hydrolases (or glycosidases). Ribbon diagram of the enzyme TIM, surrounded by the space-filling model of the protein. ... Glycoside hydrolases (also called glycosidases) catalyze the hydrolysis of the glycosidic linkage to generate two smaller sugars. ...

Glycoside hydrolases typically can act either on α- or on β-glycosidic bonds, but not on both.

Before monosaccharide units are incorporated into glycoproteins, polysaccharides or lipids in living organisms, they are typically first "activated" by being joined via a glycosidic bond to the phosphate group of a nucleotide such as Uridine diphosphate (UDP) or guanosine diphosphate (GDP). (Sometimes mono- or oligosaccharides are also activated by being linked to lipids through a phosphate or diphosphate group.) Then enzymes known as glycosyltransferases transfer the sugar unit from the activated glycosyl donor to an accepting nucleophile. Lipids are a class of hydrocarbon-containing organic compounds. ... Above is a ball-and-stick model of the inorganic hydrogenphosphate anion (HPO42−). Colour coding: P (orange); O (red); H (white). ... A nucleotide is a chemical compound that consists of a heterocyclic base, a sugar, and one or more phosphate groups. ... Uridine diphosphate, abbreviated UDP, is a nucleotide. ... Guanosine diphosphate, abbreviated GDP, is a nucleotide. ... Glycosyltransferases are a group of enzymes that act as a catalyst for the transfer of a monosaccharide from a glycosylamine derivative to an acceptor. ... In chemistry, a nucleophile (literally nucleus lover) is a reagent which is attracted to centres of positive charge. ...

External links

• Definition of glycosides, from the IUPAC Compendium of Chemical Terminology, the "Gold Book"

The International Union of Pure and Applied Chemistry (IUPAC) is an international non-governmental organization devoted to the advancement of chemistry. ... The Gold Book or Compendium of Chemical Terminology (ISBN 0865426848) is a book published by IUPAC containing internationally accepted definitions for terms in chemistry. ...

References

• Varki A et al. Essentials of Glycobiology. Cold Spring Harbor Laboratory Press; 1999. Searchable online version