Disaccharides are twomonosaccharideadoptGlycosidic bondThe connected compounds can be divided into two types according to the different connection modes: one is the non reducing sugar formed by dehydration of the semi acetal (semi ketal) hydroxyl groups of two sugars into glycosides, named glycosyl glycosides;The other is a reducing sugar formed by glycosidation of the semi acetal (semi ketal) hydroxyl group of a sugar and the non semi acetal (semi ketal) hydroxyl group of another sugar, which is named glycosyl sugar.The linking mode between sugar and sugar is indicated by numbers and arrows, which are enclosed in brackets between the names of the two sugars. If two hemiacetals (ketals) are hydroxyglycosides, they are indicated by double arrows;One sugar can also be used as another sugarOSubstituent Denomination.[2]
The names of disaccharide derivatives are similar to those of monosaccharide derivatives.[2]
effect
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NaturalFree stateAnd functional sugarsMammalsOflactose, bacteria andinsectHematologicaltrehalose, vegetalsucroseIs representative.These are the energy sources of various organisms, or the material raw materials of organisms, which play an important role in the storage or transportation of necessary sugars.On the one hand, it can be transformed from various specialGlucosidaseAnd corresponding sugarnucleosideIt can also be synthesized byCatabolic enzymeHydrolysis andphosphoric acidDisassemble.Cellobioseandmalt dustIt is also a familiar disaccharide.On the other hand, it is not so much to synthesize alone as to play its rolecelluloseAnd starch.Therefore, there is a higher structure than the naturally discovered disaccharides, and most free disaccharides are the products of their metabolic decomposition.
characteristic
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Glycosidic bondCan be accessed onmonosaccharideAny hydroxyl group of the part is formed, so even if the two monosaccharides for the synthesis of disaccharides are the same (such asglucose）The formed disaccharides also have different physical and chemical properties.
Disaccharides can be crystalline orWater solubilityOr with sweet taste.The monosaccharides that form disaccharides determine these properties.
example
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A disaccharide is a relatively large sugar formed by two monosaccharide molecules linked together by a "glycoside bond". The most common disaccharides in nature are sucrose, lactose and maltose.Disaccharides must be decomposed into monosaccharides in the human body before they can be absorbed and utilized.
lactose
Lactose is a disaccharide, its English name is Lactose;By a moleculeβ-D-galactoseAnd one moleculeβ-D-glucosestayβ-1, 4-position formationGlycosidic bondto be connected.Molecular formula CtwelveHtwenty-twoOeleven，Molar mass342.3g/mol。There are twoTerminal baseIsomer:α-lactoseandβ-lactoseAnd can be converted to each other in aqueous solution.α-Lactose easily binds to one moleculeCrystal water。
The sweetness is about one fifth of sucrose, and the 2-8% solid composition in milk islactose。YoungmammalIntestinal secretionlactaseDecompose lactose intomonosaccharide。Adult animals, including exceptCaucasian raceThe activity of lactase in most human bodies is greatly reduced.Therefore, drinking milk can cause diarrheaabdominal distentionAnd other symptoms, calledLactose intolerance 。
sucrose
Sucrose is basic to human beingsfood additivesFirst, it has a history of thousands of years.
Solubility: Extremely soluble in wateraniline , nitrobenzeneethyl acetate, alcohol and water mixture.Insoluble in gasoline, petroleumAbsolute alcohol、CHCl3, CCl4 in watersolubility: Each gram of water can dissolve 2.1 g sucrose, that is, the solubility is 210g (25 ℃), which is a kind of sugar with high solubility.
Sucrose is easy to be hydrolyzed by acid, and the same amount ofD-glucoseAnd D-fructose.Not reducible.FermentativecaramelIt can be used as a colouring agent for soy sauce.
guanyuzhetang
malt dust
Maltose iscarbohydrateIt is also a kind of traditional Chinese nostalgic snack, made of maltose. Its golden luster, stickiness and softness are the reasons why it is popular.Maltose was called maltose in ancient times《Analytical Dictionary of Characters》: "Yemi food".
In November 2022, Chinese scientists will studyIt was found that disaccharides (sweet taste) were positively selected during watermelon domestication[1]。
