Monosaccharide

The general is a monosaccharide containing 3-6 carbon atoms and more hydroxyl Polyhydroxy aldehydes or ketones. Sugar is the most simple Glyceraldehyde And two hydroxyl groups acetone . Is the basic unit of various monosaccharide sugar molecules composed of naturally occurring monosaccharide is generally D. In the Sugar formula, the monosaccharide is from 3-7 n integer, are called triose, chitosan, Pentose Sugar and sugar, has not. There would be a monosaccharide ring type structure form, can also open chain form There.
Monosaccharide

Monosaccharide Summary

Definition: the monosaccharide is no longer hydrolysis The sugar is various Two sugar The basic unit and the molecular polysaccharide.
According to the number of carbon atoms, can be divided into monosaccharides Triose Ding, sugar, Pentose Hexose, etc.. Nature is mainly pentose and monosaccharide Hexose . According to the structure, and can be divided into monosaccharides aldose and Ketosugar . Polyhydroxy aldehydes called aldose, multi hydroxyl One called ketosugar. For example, glucose Talose , fructose For sugar. The most important monosaccharide most closely relationship with the people is glucose. Common monosaccharide and fructose, Galactose , Ribose and Desoxyribose Etc..

Monosaccharide structure

Monosaccharide Ring and chain structure of monosaccharides

The chain structure of 1 monosaccharides
Method of determining chain structure (glucose):
2 monosaccharide ring structure
In solution, monosaccharide containing more than 4 carbon atoms in the main ring structure.
Monosaccharide molecules in hydroxyl and aldehyde or ketone based inverse semi acetal condensation ring (emiacetal). Ring After the carbonyl C becomes a chiral C atom called heterogeneous end carbon atom (anomeric carbon atom), the two form a ring after Diastereoisomers Be called End group Isomer, isomer or head (anomer), called the alpha - and beta type head isomers.
The ring structure with the general Haworth structure representation:
With Fischer projection said ring structure is very convenient. Haworth type structure can correctly reflect the sugar molecules in the more than Fischer projection Bond angle And the length of the key. Conversion method:
The painting of a five round or six ring
From the right side of the anomeric carbon oxygen atom (anomerio carbon), painting Hemiacetal hydroxyl In Fischer, on the right side of the projection in the ring, left in the ring.
The molecular formula of glucose was C6H12O6, containing five hydroxyl groups and an aldehyde molecule, is aldohexose. The C-2, C-3, C-4 and C-5 are different chiral carbon Atom, 16 (alpha 4=16) with Optical rotation Isomer, D- glucose Is one of them. Exists in the nature of the glucose Fischer Projection, four Chiral carbon atom In addition to C-3 -OH on the left, the other chiral carbon atoms on the -OH are on the right.
Determination of monosaccharide configuration is still using the D/L method. This method only consider carbonyl A chiral carbon configuration are far away from each other, the chiral carbon hydroxy on type D on the right, the left in L. There are many monosaccharides belong to D type sugar.

Monosaccharide The ring structure and the glucose mutarotation

The crystallization of glucose has two kinds, one is crystallized from ethanol, the melting point of 146 DEG C. [a]D with a new solution which is +112 degrees, the solution is in place, decreased specific rotation at +52.17 DEG after remain unchanged; the other is from pyridine Crystallized, the melting point of 150 DEG C, [alpha]D with a new solution for +18.7 degrees, the solution is in place, specific rotation gradually Rose, also reached +52.7 degrees after unchanged. Sugar in solution, specific rotation to change fixed value of the phenomenon is called mutarotation. Obviously glucose open chain structure can not explain this phenomenon.
The open chain structure visible from glucose, which has aldehyde groups, have hydroxyl in the interior of the molecule, it can form cyclic hemiacetal.
Ring, carbonyl and hydroxyl groups on C-5 glucose via addition reaction to form stable six membered ring. Although with glucose molecules Aldehyde But, in the reaction performance and general aldehydes have many differences, such as the addition of NaHSO3 is very slow, its reason is in solution, glucose almost to the hemiacetal ring exists for the sake of.
Ring, the carbonyl carbon atom (C-1) into the original chiral carbon atom Hemiacetal hydroxyl, newly formed C-1 in the spatial arrangement of two possible. Hemiacetal hydroxyl and hydroxyl decided monosaccharide configuration (C-5 hydroxyl) in Carbon chain Called the alpha type on the same side, in the opposite side of the called beta type. Alpha and beta type is non Enantiomer . The difference is the C-1 configuration, so it is also called Anomer (anomer). The melting point and specific rotation are different.
Grape Mutarotation of sugar, is due to open chain structure and ring structure form a balanced system in the process of specific rotation caused by the change of. In the solution of alpha -D- glucose can be converted to open chain structure, then the structure of open chain into beta -D- glucose; glucose is also beta -D- into chain structure, and then transformed into alpha -D- glucose. After a period of time, three isomers of balance, form a Tautomerism The balance system, the specific rotation of no longer change.
Not only the grapes to mutarotation, who can form a monosaccharide ring structure, will produce mutarotation.

Monosaccharide Haworth type and conformation type ring structure

The upright ring Fischer projection Although it can be said, monosaccharide ring structure, spatial arrangement but also can not accurately reflect the monosaccharide molecules in each atom or radical. This suggested the use of perspective to haworth. Haworth will ring ring into vertical plane. Because the glucose ring type structure is composed of five carbon atoms and one Oxygen atom Consisting of heterocyclic compounds, and it Heterocyclic compounds In Pyran Similar, so called Pyranose . Written respectively attached to the ring atom or group of atoms in the ring above and below to indicate the position of the arrangement.
Writing haswah type is often dropped into a ring of carbon atoms, and the three C-C button towards the front is represented by thick lines.
The D type glucose, hydroxyl ring on the right side of the upright, in the ring plane below the Haas formula; the left side of the upright ring above the plane of the ring hydroxyl group. The ring, in order to make C-5 and hydroxyl Aldehyde Close. C (4) -C (5) single to be rotated 120 degrees. Therefore, hydroxymethyl D type sugar at the end of that is in the ring above the plane. The newly formed on C-1 Hemiacetal The plane of the ring is below the hydroxy alpha type; the plane of the ring above is called beta type.
In abundance, the formation of the various atomic pyran ring, not in a plane, but in a more stable chair conformation. Therefore, in order to better reflect its structure, it is used to express the conformation.
A -D- C-1 -OH in addition to D-glucopyranose even in a key, the other three carbon on the -OH and -CH2OH are connected to the e bond, and beta -D glucopyranose on C-1 -OH and all the larger clusters (-OH, -CH2OH) are connected to the e bond, and the conformation of beta type more stable. It reached equilibrium in solution, beta and alpha type accounted for 64%, accounted for only 36%. configuration
Configuration of monosaccharides (configuration): D type and L type chain structure,
An isomer of the plane of polarization of polarized surface clockwise deflection, is called the right optical material, with + said. Another isomer makes polarization plane polarized along the counterclockwise deflection, left rotation matter, said -.

Monosaccharide Nature

Monosaccharide Physical property

Monosaccharide is a colorless crystal, sweet, hygroscopicity. Easily soluble in water, insoluble in ethanol, insoluble in Ether . Monosaccharide has optical activity, its solution is Mutarotation .

Monosaccharide Chemical property

Monosaccharide ring structure mainly exists in the form, but in the solution and structure of open chain reaction. Therefore, the chemical reaction to some monosaccharide ring type structure, some with open chain structure.

Monosaccharide Epimerization

Dilute alkali treatment with glucose, will change as part of mannose And a complex mixture of fructose. This change is accomplished through enol intermediates.
D- fructose D- D-, mannose and glucose C-3.C-4, C-5 and C-6 have the same structure, only the structure of C-1 and C-2 are different, but their C-1, C-2 structure into enol form, the structure of the same. Therefore, not only is D- and D- or D- glucose, fructose mannose in dilute alkali catalysis, can three of the tautomeric mixture.
In between containing multiple chiral carbon atoms of optically active isomers, where only one configuration of chiral carbon atom is not at the same time, each called epimers. D- D- is the C-2 of glucose and mannose Epimers . Therefore, called treatment with dilute alkali D- glucose equilibrium mixture of D- glucose, D- fructose three substances reaction Epimerization .

Monosaccharide Oxidation

Monosaccharide either aldoses or ketoses may be weak oxidant Yellen, Fehling reagent and reagent Benedict Effect of low oxide formation of metal or metal. These three reagents are alkaline weak oxidizing agent. Monosaccharide heating in alkaline solution, generating complex mixtures.
Monosaccharide is easy to weak alkaline oxidation shows that they have reduced, so called them reducing sugar .
Monosaccharide oxidation in acidic conditions, due to the different oxidant strength, oxidation products of monosaccharides are also different. For example, glucose is bromine oxidation, generation Gluconic acid And use; Strong oxidizer Nitric acid oxidation, generating glucaric acid.
Bromine oxidation ability is weak, the aldose Aldehyde Oxidized to carboxyl. When adding bromine aldose, slightly heated, water can be faded brown, and sugar was not oxidized, so it can be used to distinguish between aldose and bromine Ketosugar .

Monosaccharide Effect of glycosides

Hemiacetal hydroxyl monosaccharide cyclic hemiacetal structure with another molecule of alcohol or hydroxyl function, remove a molecule of water and formation of acetal. This is called sugar acetal Glycoside . For example, alpha and beta -D- glucopyranose mixture in hydrogen chloride The catalytic reaction of methanol from below, a water molecule to generate alpha and beta -D- methyl pyran Glucoside The mixture.
Alpha and beta -D- pyran grape mixture of beta -D- methyl glucopyranoside alpha -D- methyl glucopyranoside, glycosides from sugar and non sugar components. The noncarbohydrate part is called Aglycone or Aglycone . Through the "oxygen bridge" sugar and aglycone after dehydration connection, this bond is called Glycoside bond . The ring type structure of monosaccharides have alpha - and beta two configurations, so can generate alpha - and beta two no configuration in. For the beta configuration of natural glycosides. Is the name of the glycoside named according to their composition, and pointed out that the glycoside bond and sugar. According to the sources of natural glycosides often used common name.
No hemiacetal hydroxyl has glycosidic structure, can be transformed into aldehyde type open chain structure in solution, so no reducing sugar workers was no mutarotation. Glucoside was stable in neutral or alkaline environment, but in acidic solution or under the action of the enzyme, then hydrolyzed sugar and non sugar part.
Glucoside is one of the effective ingredients of Chinese herbal medicine, is colorless, odorless solid, bitter taste, but glycosides and flavonoids as yellow anthraquinone glycoside.
Glycoside contains sugar, so it can be dissolved in water. Glycosides are optically active, more natural glycosides L .

Monosaccharide Effect of ester

Containing multiple hydroxyl monosaccharide molecules, these can react with acids to produce esters. The human body generates glucose glucose phosphate under the action of the enzyme, such as 1- and 6- phosphate phosphate D-glucopyranose D-glucopyranose etc..
Monosaccharide phosphate Has an important significance in the process of life, which is the intermediate product of many metabolism in human body.

Monosaccharide Osazone reaction

Three monosaccharide molecules and molecular effects of phenylhydrazine product, called maltobiose. For example, excess glucose and phenylhydrazine, generation Grape Osazone.
Whether it is or can aldose ketose osazones, osazone reaction can be regarded as the specific reaction of alpha hydroxy aldehyde or alpha hydroxy ketone.
Maltobiose yellow crystal is difficult to dissolve in water. Different phenylosazone has the characteristics of crystal shape and the melting point. Often use maltobiose and these properties to identify the different sugar.
Osazone reaction occurs only in the C-1 and C-2 of monosaccharide molecules, does not involve other carbon atoms, besides C-1 and C-2 carbon atoms of the same configuration of sugar, can generate the same maltobiose. For example: D- glucose and D- fructose phenylosazone produce the same.

Monosaccharide Reduction reaction

Monosaccharides may be reduced to the corresponding sugar alcohol (Sugar alcohol).
D- glucose was reduced to D- glucose alcohol, also known as Shan Li alcohol (D-Sorbitol).
Sugar alcohol is mainly used in food processing and medicine, add alcohol to Shan Li candy Can prolong the shelf life of candy candy, because it can prevent water loss. The saccharin treated juice generally have after taste, add d-Sorbitol After removal of the after taste. The human body after eating, Shan Li alcohol in the liver and converted to fructose.

Monosaccharide Monosaccharide classification

Monosaccharides have been found in nature is mainly pentose and hexose. Common pentose D- (-) - Ribose D- (-) -2- Desoxyribose And (+) - D- xylose And (+) - L- Arabia sugar . They are an polysaccharide glycoside or exist in the form of animals and plants. Common hexose D- (+) D- (+) - glucose, mannose, D- (+) - Galactose And D- (-) - the latter is fructose, sugar. Hexose to free or combined form in plants.

Monosaccharide Ribose

In the form of RNA glucoside in yeast and cells, nucleic acids and certain enzymes and vitamins composition divided into. In addition to DNA and 2- RNA, deoxyribose (referred to as desoxyribose).
Ribose and deoxyribose ring for the furan ring, called furanoses.
Beta -D - (-) - ribofuranose beta -D- (-) - deoxy furan Ribonucleic acid The ribose or deoxyribose C-1 beta glycosidic bond with ribonucleoside or Deoxyriboside Collectively, nucleoside.
Nucleoside ribose or deoxyribose, with hydroxyl and phosphate C-5 or C-3 with ester bond with a nucleotide . The nucleotide containing ribose referred to as Ribonucleotide That is the basic unit of RNA; nucleotide containing deoxyribose are called Deoxyribotide That is the basic unit of DNA.

Monosaccharide Glucose

D- (+) - glucose is widely distributed in nature, especially in the more content of grapes, so called glucose. Glucose also exists in human blood (called 389-555umol/l) blood sugar . In the urine of diabetics contains glucose, sugar content with the severity and different. Is a lot of sugar such as sucrose and glucose, Malt dust , lactose And starch, Glycogen The unit, composed of cellulose.
Glucose is a colorless crystal or white crystalline powder, the melting point of 146 DEG C, soluble in water, insoluble in alcohol Sweet. Natural dextrorotatory glucose is so called. Dextrose .
In the liver, glucose in enzyme oxidation of grape Uronic acid That is, hydroxymethyl glucose is generated on the end of carboxyl oxide.
Glucuronic acid and toxic substances such as alcohol and phenol combined into non-toxic compounds excreted by urine in the liver, can be reached Detoxification .

Monosaccharide Galactose

Galactose and glucose combined with lactose in the milk, exist in mammals,. In some brain cerebroside complex also contains galactose.
Galactose is aldose is glucose diastereomerically. The two differ only in the C-4 configuration on the contrary, the two C-4 epimer. Galactose has ring structure, the C-1 also has alpha - and beta two configurations.
Alpha -D- beta -D- galactopyranose galactopyranose
Galactose is a colorless crystal, melting point of 165-166 deg.. half lactose Yes Reduction Also, mutarotation, balance the specific rotation of +83.3 degrees.
The human body is galactose hydrolysis product of lactose in food intake. Under the catalysis of the enzyme galactose can be transformed into glucose.
Some derivatives of galactose are widely distributed in the plant kingdom. For example, Galacturonic acid Is the main component of plant mucus; also called agar gel 9 agar ) is composed of polymer galactose derivatives.

Monosaccharide fructose

D- fructose found free in fruits and honey, is a unit of sucrose, prostate and in animal semen Also contains a considerable amount of fructose.
Fructose is a colorless crystal, easily soluble in water, the melting point of 105 DEG C. D- fructose Laevulose Also, mutarotation, balance the specific rotation of -92 degrees. This balance system is a mixture of open chain and cyclic fructose.
Beta -D- (-) - fructophyranose beta -D- (-) - fructofuranose
Fructose under free state, mainly exists in the form of pyran ring: in combination with the state is more of a furan ring form.
Fructose can also form phosphate, fructose -6- phosphate body (F-6-) and fructose -1 6- two phosphate, F-1, 6- two).
Fructose phosphate in vivo Glucose metabolism The important intermediate products, has played an important role in sugar metabolism. F-1, 6- two catalyzed by enzymes, can be generated Glyceraldehyde -3- phosphate and two hydroxyl groups acetone Phosphate.
In vivo through this reaction into triose hexose, which is an intermediate step in the process of glucose metabolism. This reaction is similar to the reverse reaction of aldol condensation reaction.

Monosaccharide Amino sugar

The nature of the amino sugar is hydroxyl on the C-2 molecule is aldohexose amino substituted derivatives.
Beta -D- glucosamine beta -D- galactosamine
Amino sugar found in protein and in combination with the state glycoprotein However, the free amino galactose toxicity in the liver.

Monosaccharide Uronic acid

Uronic acid (alduroic acid) - from the most distant aldose aldehyde is oxidized carboxyl Sugar into acid. The existence of natural uronic acid D- glucose, 3 D- mannose hexuronic acid and D- galactose derivative, which is an important animal and plant and microbial polysaccharides, which only Galacturonic acid Can the free state exists in plant fruit. In animal in vivo, D- glucuronic acid A Detoxification The function of. Many kinds of aglycone binding and D- glucuronic acid, are generally small molecular compounds, including phenols, aromatic acid, fatty acid, Aromatic hydrocarbon Etc.. Usually the aglycone and D- glucuronic acid 1: the proportion of 1, with few exceptions. The main binding site in the liver.

Monosaccharide Deoxysugar

Compound monosaccharide hydroxyl groups are formed by substitution of hydrogen. Such as D-2- Desoxyribose DNA component; L- fucose into glycoproteins composition, it is L-6- - galactose.

Monosaccharide Two nucleoside phosphate sugar

Two nucleotide sugar phosphate (nucleoside diphosphate sugar) compounds of monosaccharide and nucleoside two phosphate terminal phosphate group with the glycosidic bond formed by the connection. The activation of the sugar radical is involved in many metabolic reactions, especially oligosaccharides and polysaccharides biosynthesis . As of now, study the natural nucleoside two sugar phosphate has more than 100 kinds, such as nucleoside two glucose phosphate was UDP- glucose, ADP- glucose, CDP- glucose, GDP- glucose, TDP- glucose 5. Uridine two phosphogluconic (uridine diphosphate glucose, UDPG) as the representatives two sugar nucleoside phosphate.

Monosaccharide absorb

Sugar has been digested into monosaccharides in the small intestine, intestinal epithelial cells could be absorbed into the blood. According to the absorption rate Can be divided into two categories: monosaccharide galactose and glucose, which belongs to a kind of quick absorption; fructose is belong to a class of slow absorption.
(glucose or galactose) absorption and Na+ coupling, the two together using a carrier protein in intestinal epithelium striated border on. Because the concentration of intestinal cavity is higher than the Na+ cells, and Na+ Carrier protein Combine the concentration difference into cells, as long as the intestinal cavity to maintain a high concentration of Na+, you can take the initiative to glucose transport into the cell, until the intestinal cavity of glucose transport all finished. When Na+ and glucose into the cells, and the carrier from Na+ by the sodium pump cell side of the membrane active transport in intercellular space. Glucose molecules to diffuse through the side of the membrane, and At the end of the film Out of the cell (Figure 8-9). In the intestinal lumen may be through fructose Easy Diffusion transport into the villi.