Monosaccharide

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Monosaccharide

Monosaccharides (from Greek

Greek language

Greek is an Indo-European languages native to the southern Balkan peninsula, the language of the Greek people. It forms an independent branch within Indo-European....
monos: single, sacchar: sugar) are the most basic unit of carbohydrate

Carbohydrate

Carbohydrates or saccharides are the most abundant of the four major classes of biomolecules. They fill numerous roles in living things, such as the storage and transport of energy and structural components ....
s. They are the simplest form of sugar

Sugar

Sugar is a class of edible crystalline substances, mainly sucrose, lactose, and fructose. Human taste buds interpret its flavor as sweet. Sugar as a basic food carbohydrate primarily comes from sugar cane and from sugar beet, but also appears in fruit, honey, sorghum, sugar maple , and in many other sources....
and are usually colorless, water

Water

Water is a common chemical substance that is essential for the survival of all known forms of life. In typical usage, water refers only to its liquid form or States of matter, but the substance also has a solid state, ice, and a gaseous state, water vapor or steam....
-soluble, crystalline

Crystal

A crystal or crystalline solid is a solid material whose constituent atoms, molecules, or ions are arranged in an orderly repeating pattern extending in all three spatial dimensions....
solids. Some monosaccharides have a sweet taste

Sweetness

Sweet is one of the five basic tastes and is almost universally regarded as a pleasure experience. Foods rich in simple carbohydrates such as sugar are those most commonly associated with sweetness, although there are other natural and artificial compounds that are much sweeter, some of which have been used as sugar substitutes for those wi...
. Examples of monosaccharides include glucose

Glucose

Glucose , a monosaccharide also known as grape sugar, blood sugar, or corn sugar, is a very important carbohydrate in biology....
(dextrose), fructose

Fructose

Fructose is a simple Reducing sugar sugar found in many foods and is one of the three important dietary monosaccharides along with glucose and galactose....
(levulose), galactose

Galactose

Galactose is a type of Carbohydrate which is less sweetness than glucose. It is considered a nutritive sweetener because it has food energy.Galactan is a polymer of the sugar galactose....
, xylose

Xylose

Xylose, or wood sugar, is an aldopentose — a monosaccharide containing five carbon atoms and including an aldehyde functional group. It has chemical formula 5105....
and ribose

Ribose

Ribose, primarily occurring as D-ribose, is an organic compound that occurs widely in nature. It is an aldopentose, that is a monosaccharide containing five carbon atoms that, in its acyclic form, has an aldehyde functional group at one end....
. Monosaccharides are the building blocks of disaccharide

Disaccharide

A disaccharide is a sugar composed of two monosaccharides.'Disaccharide' is one of the four chemical groupings of carbohydrates ....
s such as sucrose

Sucrose

Sucrose is a disaccharide of glucose and fructose, with the molecular formula C12H22O11. Its systematic name is a-D-glucopyranosyl- -?-D-fructofuranoside ....
and polysaccharide

Polysaccharide

Polysaccharides are relatively complex carbohydrates. They are polymers made up of many monosaccharides joined together by glycosidic bonds. They are therefore very large, often branched, macromolecules....
s (such as cellulose

Cellulose

File:Cellulose Sessel.svgCellulose is an organic compound with the chemical formula , a polysaccharide consisting of a linear chain of several hundred to over ten thousand ? linked D-glucose units....
and starch

Starch

File:Amylose2.svgFile:Amylopektin Sessel.svgStarch or amylum is a polysaccharide carbohydrate consisting of a large number of glucose units joined together by glycosidic bonds....
). Further, each carbon atom that supports a hydroxyl

Hydroxyl

Hydroxyl in chemistry stands for a molecule consisting of an oxygen atom and a hydrogen atom connected by a covalent bond. The neutral form is a hydroxyl Radical and the hydroxyl anion is called a hydroxide....
group (except for the first and last) is chiral

Chirality (chemistry)

The term chiral is used to describe an object that is non-Superposition on its mirror image.Human hands are perhaps the most universally recognized example of chirality: The left hand is a non-superposable mirror image of the right hand; no matter how the two hands are oriented, it is impossible for all the major features of both hands...
, giving rise to a number of isomeric

Isomer

In chemistry, isomers are compounds with the same molecular formula but different structural formulae. Isomers do not necessarily share similar properties unless they also have the same functional groups....
forms all with the same chemical formula.

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Structure

With few exceptions (e.g., deoxyribose

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 in its linear structure....
), monosaccharides have the chemical formula

Chemical formula

A chemical formula is a way of expressing information about the atoms that constitute a particular chemical compound, and how the relationship between those atoms changes in chemical reactions....
C_x(H₂O)_y with the chemical structure H(CHOH)_nC=O(CHOH)_mH. If n or m is zero, it is an aldehyde and is termed an aldose

Aldose

An aldose is a monosaccharide containing one aldehyde group per molecule and having a chemical formula of the form Cnn....
, otherwise it is a ketone and is termed a ketose

Ketose

A ketose is a sugar containing one ketone group per molecule.With 3 carbon atoms, dihydroxyacetone is the simplest of all ketoses and is the only one having no optical activity....
. Monosaccharides contain either a ketone

Ketone

In organic chemistry, a ketone is a type of organic compound which contains a carbonyl group bonded to two other carbon atoms in the form:Neither of the substituents R1 and R2 may be equal to hydrogen ....
or aldehyde

Aldehyde

An aldehyde is an organic compound containing a terminal carbonyl group. This functional group, which consists of a carbon atom bonded to a hydrogen atom and double bond to an oxygen atom , is called the aldehyde group....
functional group

Functional group

In organic chemistry, functional groups are specific groups of atoms within molecules that are responsible for the characteristic chemical reactions of those molecules....
, and hydroxyl

Hydroxyl

Carbonyl

In organic chemistry, a carbonyl group is a functional group composed of a carbon atom double bond to an oxygen atom : C=O.The term carbonyl can also refer to carbon monoxide as a ligand in an inorganic or organometallic complex ; in this situation, carbon is triple-bonded to oxygen : C=O....
carbon atom

Atom

|-! bgcolor=gray | Properties|-||}The atom is a basic unit of matter consisting of a dense, central atomic nucleus surrounded by a electron cloud of electric charge electrons....
s.

Fischer projections

Not all of the following monosaccharides are found in nature—some have been synthesized:

Aldoses
aldotriose	D-glyceraldehyde Glyceraldehyde Glyceraldehyde is a triose monosaccharide with chemical formula Carbon3Hydrogen6Oxygen3. It is the simplest of all common aldoses....
aldotetroses	D-erythrose Erythrose Erythrose is a tetrose carbohydrate with chemical formula Carbon4Hydrogen8Oxygen4. It has one aldehyde group and so is part of the aldose family. The natural isomer is D-erythrose....				D-threose Threose Threose is a tetrose carbohydrate with chemical formula 484. It has one aldehyde group and so is part of the aldose family. It exists in both D and L stereoisomers....
aldopentoses	D-ribose Ribose Ribose, primarily occurring as D-ribose, is an organic compound that occurs widely in nature. It is an aldopentose, that is a monosaccharide containing five carbon atoms that, in its acyclic form, has an aldehyde functional group at one end....		D-arabinose Arabinose Arabinose is an aldopentose — a monosaccharide containing five carbon atoms, and including an aldehyde functional group. It has chemical formula Carbon5Hydrogen10Oxygen5 and a molar mass of 150.13 g/mol....		D-xylose Xylose Xylose, or wood sugar, is an aldopentose — a monosaccharide containing five carbon atoms and including an aldehyde functional group. It has chemical formula 5105....		D-lyxose Lyxose Lyxose is an aldopentose — a monosaccharide containing five carbon atoms, and including an aldehyde functional group. It has chemical formula 5105....
aldohexoses	D-allose Allose Allose is an aldohexose sugar. It is a rare monosaccharide that has been isolated from the leaves of the African shrub Protea rubropilosa. It is soluble in water and practically insoluble in methanol....	D-altrose Altrose Altrose is an aldohexose sugar. D-Altrose is an unnatural monosaccharide. It is soluble in water and practically insoluble in methanol....	D-glucose Glucose Glucose , a monosaccharide also known as grape sugar, blood sugar, or corn sugar, is a very important carbohydrate in biology....	D-mannose Mannose Mannose is a sugar monomer of the hexose series of carbohydrates....	D-gulose Gulose Gulose is an aldohexose sugar. It is an unnatural monosaccharide that exists as a syrup with a sweet taste. It is soluble in water and slightly soluble in methanol....	D-idose Idose Idose is a hexose, a six carbon monosaccharide. It has an aldehyde group and is an aldose. It is not found in nature, but its uronic acid, iduronic acid, is important....	D-galactose Galactose Galactose is a type of Carbohydrate which is less sweetness than glucose. It is considered a nutritive sweetener because it has food energy.Galactan is a polymer of the sugar galactose....	D-talose Talose Talose is an aldohexose sugar. It is an unnatural monosaccharide that is soluble in water and slightly soluble in methanol. Some etymologists suggest that talose's name derives from the automaton of Greek mythology named Talos, but the relevance is unclear....

Ketoses
ketotriose	dihydroxyacetone Dihydroxyacetone Dihydroxyacetone is a simple carbohydrate that is primarily used as an ingredient in sunless tanning products. It is often derived from plant sources such as sugar beets and sugar cane, by the fermentation of glycerin....
ketotetrose	D-erythrulose Erythrulose D-Erythrulose is a tetrose carbohydrate with the chemical formula Carbon4Hydrogen8Oxygen4. It has one ketone group and so is part of the ketose family....
ketopentoses	D-ribulose Ribulose Ribulose is a ketopentose — a monosaccharide containing five carbon atoms, and including a ketone functional group. It has chemical formula 5105....		D-xylulose Xylulose Xylulose is a ketopentose, a monosaccharide containing five carbon atoms, and including a ketone functional group. It has the chemical formula 5105....
ketohexoses	D-psicose Psicose D-Psicose is an ultralow-energy monosaccharide sugar. It is a C-3 epimer of D-fructose, and is present in small quantities in agricultural products and commercially-prepared carbohydrate complexes....	D-fructose Fructose Fructose is a simple Reducing sugar sugar found in many foods and is one of the three important dietary monosaccharides along with glucose and galactose....	D-sorbose Sorbose Sorbose is a ketose belonging to the group of sugars known as monosaccharides. The commercial production of vitamin C often begins with sorbose. L-Sorbose is the configuration of the naturally-occurring sugar....	D-tagatose Tagatose Tagatose is a functional sweetener. It is a naturally occurring monosaccharide, specifically a hexose. It is often found in dairy products, and is very similar in texture to sucrose and is 92% as sweet, but with only 38% of the calories....

Monosaccharides with even longer chains are known, such as the ketoheptoses, mannoheptulose

Mannoheptulose

Mannoheptulose is a hexokinase inhibitor. It is a heptose, a monosaccharide with seven carbon atoms. By blocking the enzyme hexokinase, it prevents glucose phosphorylation....
and sedoheptulose

Sedoheptulose

Sedoheptulose or D-altro-heptulose is a ketoheptose — a monosaccharide with seven carbon atoms and a ketone functional group. It is one of the few heptoses found in nature....
.

Cyclic structure

Most monosaccharides will cyclize in aqueous solution, forming hemiacetal

Hemiacetal

Hemiacetals and hemiketals are compounds of the general formula R1R'1COR2, where R2 is not hydrogen....
s or hemiketals (depending on whether they are aldoses or ketoses) between an alcohol and the carbonyl group of the same sugar. Glucose

Glucose

Glucose , a monosaccharide also known as grape sugar, blood sugar, or corn sugar, is a very important carbohydrate in biology....
, for example, readily forms a hemiacetal

Hemiacetal

Hemiacetals and hemiketals are compounds of the general formula R1R'1COR2, where R2 is not hydrogen....
linkage between its carbon₁ and oxygen₅ to form a 6-membered ring called a pyranoside. The same reaction can take place between carbon₁ and oxygen₄ to form a 5-membered furanoside. In general, pyranosides are more stable and are the major form of the monosaccharide observed in solution. Since cyclization forms a new stereogenic center at carbon₁, two anomer

Anomer

In sugar chemistry, an anomer is a special type of epimer. It is a stereoisomer of a saccharide that differs only in its configuration at the hemiacetal carbon, also called the anomeric carbon....
s can be formed (a-isomer and ß-isomer) from each distinct straight-chain monosaccharide. The interconversion between these two forms is called mutarotation

Mutarotation

'Mutarotation is the term given to the change in the specific rotation of a cyclic monosaccharide as it reaches an equilibrium between its α and β anomeric forms....
.

A common way of representing the structure of monosaccharides is the Haworth projection

Haworth projection

A Haworth projection is a common way of representing the cyclic Structural formula of monosaccharides with a simple three-dimensional perspective....
. In a Haworth projection, the a-isomer has the OH- of the anomeric carbon below the plane of the carbon atoms, and the ß-isomer, has the OH- of the anomeric carbon above the plane. Monosaccharides typically adopt a chair conformation, similar to cyclohexane

Cyclohexane

Cyclohexane is a cycloalkane with the molecular formula Carbon6Hydrogen12. Cyclohexane is used as a nonpolar solvent for the chemical industry, and also as a raw material for the industrial production of adipic acid and caprolactam, both of which are intermediates used in the production of nylon....
. In this conformation the a-isomer has the OH- of the anomeric carbon in an axial position, whereas the ß-isomer has the OH- of the anomeric carbon in equatorial position.

Monosaccharide nomenclature

Monosaccharides are classified by the number of carbon

Carbon

Carbon is a chemical element with chemical symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalence?making four electrons available to form covalent bond chemical bonds....
atoms they contain:

Triose
Triose

A triose is a monosaccharide containing three carbon atoms. There are only two trioses, an aldotriose and a ketotriose . Trioses are important in Cellular respiration....
, 3 carbon atoms
Tetrose
Tetrose

A tetrose is a monosaccharide with 4 carbon atoms. They either have an aldehyde functional group in position 1 or a ketone functional group in position 2 ....
, 4 carbon atoms
Pentose
Pentose

A pentose is a monosaccharide with five carbon atoms.They either have an aldehyde functional group in position 1 , or a ketone functional group in position 2 ....
, 5 carbon atoms
Hexose
Hexose

In organic chemistry, a hexose is a monosaccharide with six carbon atoms, having the chemical formula C6H12O6. Hexoses are classified by functional group, with aldohexoses having an aldehyde at position 1, and ketohexoses having a ketone at position 2....
, 6 carbon atoms
Heptose
Heptose

A heptose is a monosaccharide with seven carbon atoms.They either have an aldehyde functional group in position 1 , or a ketone functional group in position 2 ....
, 7 carbon atoms

Monosaccharides are classified the type of carbonyl

Carbonyl

Functional group

In organic chemistry, functional groups are specific groups of atoms within molecules that are responsible for the characteristic chemical reactions of those molecules....
they contain:

Aldose
Aldose

An aldose is a monosaccharide containing one aldehyde group per molecule and having a chemical formula of the form Cnn....
, -CHO (aldehyde
Aldehyde

An aldehyde is an organic compound containing a terminal carbonyl group. This functional group, which consists of a carbon atom bonded to a hydrogen atom and double bond to an oxygen atom , is called the aldehyde group....
)
Ketose
Ketose

A ketose is a sugar containing one ketone group per molecule.With 3 carbon atoms, dihydroxyacetone is the simplest of all ketoses and is the only one having no optical activity....
, C=O (ketone
Ketone

In organic chemistry, a ketone is a type of organic compound which contains a carbonyl group bonded to two other carbon atoms in the form:Neither of the substituents R1 and R2 may be equal to hydrogen ....
)

Isomerism

The total number of possible stereoisomers of one compound (n) is dependent on the number of stereogenic centers (c) in the molecule. The upper limit for the number of possible stereoisomers is n = 2^c. The only carbohydrate without an isomer is dihydroxyacetone

Dihydroxyacetone

Dihydroxyacetone is a simple carbohydrate that is primarily used as an ingredient in sunless tanning products. It is often derived from plant sources such as sugar beets and sugar cane, by the fermentation of glycerin....
or DHA.

Monosaccharides are classified according to their molecular configuration

Molecular configuration

The configuration of a molecule is the permanent geometry that results from the space arrangement of its chemical bond. The ability of the same set of atoms to form two or more molecules with different configurations is stereoisomerism....
at the chiral carbon furthest removed from the aldehyde or ketone group. The chirality at this carbon is compared to the chirality of carbon 2 on glyceraldehyde

Glyceraldehyde

Glyceraldehyde is a triose monosaccharide with chemical formula Carbon3Hydrogen6Oxygen3. It is the simplest of all common aldoses....
. If it is equivalent to D-glyceraldehyde's C2, the sugar is D; if it is equivalent to L-glyceraldehyde's C2, the sugar is L. Due to the chirality of the sugar molecules, an aqueous solution of a D or L saccharides will rotate light. D-glyceraldehyde causes polarized light to rotate clockwise (dextrorotary); L-glyceraldehyde causes polarized light to rotate counterclockwise (levorotary). Unlike glyceraldehyde, D/L designation on more complex sugars is not associated with their direction of light rotation. Since more complex sugars contain multiple chiral carbons, the direction of light rotation cannot be predicted by the chirality of the carbon that defines D/L nomenclature.

D, configuration as in D-glyceraldehyde
Glyceraldehyde

Glyceraldehyde is a triose monosaccharide with chemical formula Carbon3Hydrogen6Oxygen3. It is the simplest of all common aldoses....
L, configuration as in L-glyceraldehyde
Glyceraldehyde

Glyceraldehyde is a triose monosaccharide with chemical formula Carbon3Hydrogen6Oxygen3. It is the simplest of all common aldoses....

All these classifications can be combined, resulting in names like D-aldohexose or ketotriose.

Monosaccharide

Structure

Fischer projections

Cyclic structure

Monosaccharide nomenclature

Isomerism

See also

External links