monosaccharides galactose and glucose Learning Goal Describe the monosaccharide units and linkages in disaccharides Disaccharides A disaccharide consists of two monosaccharides linked together ID: 933377
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Slide1
15.5 Disaccharides
Lactose is a disaccharide found in milk and milk products. It contains the monosaccharides galactose and glucose.
Learning Goal Describe the monosaccharide units and linkages in disaccharides.
Slide2Disaccharides
A disaccharide
consists of two monosaccharides linked together.is formed when two monosaccharides combine in a dehydration reaction. Monosaccharides Disaccharide glucose + glucose maltose + H2O glucose + galactose lactose + H2O
glucose + fructose
sucrose
+ H
2
O The most common disaccharides are maltose, lactose, and sucrose.
Slide3Maltose
Maltose is a disaccharide also known as malt sugar.composed of two
D-glucose molecules.obtained from the hydrolysis of starch.used in cereals, candies, and brewing.found in both the α and β forms.
Slide4Formation of Maltose
Maltose is linked by an α-(1 4)-glycosidic bond formed from the α —
OH on carbon 1 of the first glucose and the— OH on carbon 4 of the second glucose.
Slide5Lactose, Milk Sugar
Lactose is a disaccharide found in milk and milk products.makes up 6–8% of human milk and about 4–5% of cow’s milk.
Slide6Lactose
Lactose is a disaccharide of β-D-
galactose and α- or β-D-glucose.The bond in lactose is a β-(1 4)-glycosidic bond because the — OH group on carbon 1 of β-D-galactose forms a glycosidic bond with the — OH group on carbon 4 of a D-glucose molecule.
Slide7Sucrose, Table Sugar
Sucrose, or table sugar,consists of
α-D-glucose and β-D-fructose.has an α,β-(1 2)-glycosidic bond between carbon 1 of glucose and carbon 2 of fructose.
Slide8Sucrose
Sucrose cannotform an open chain or be oxidized.react with Benedict’s reagent and is not a reducing sugar.
The sugar we use to sweeten our cereal, coffee, or tea is sucrose. Most of the sucrose for table sugar comes from sugar cane (20% by mass) or sugar beets (15% by mass).
Slide9Chemistry Link to Health:
Sweetness of SweetenersSugars and artificialsweetenersdiffer in sweetness.are compared to sucrose (table sugar), which is assigned a value of 100.
Slide10Chemistry Link to Health:
Sweetness of SweetenersSucralose is marketed as Splenda.
made from sucrose by replacing some of the hydroxyl groups with chlorine atoms.
Slide11Chemistry Link to Health:
Sweetness of SweetenersAspartame, which has some caloric value, is marketed as NutraSweet or Equal.a
noncarbohydrate sweetener made from aspartic acid and a methyl ester of the amino acid phenylalanine.so sweet that a very small quantity is needed.
Slide12Chemistry Link to Health:
Sweetness of SweetenersNeotame, another artificial sweetener, is a modification of the aspartame structure.
differs by the addition of a large alkyl group to the amine group, which prevents enzymes from breaking the amide bond between aspartic acid and phenylalanine, so phenylalanine is not produced.is very sweet; only small amounts of Neotame are needed because it is about 10 000 times sweeter than sucrose
Slide13Chemistry Link to Health:
Sweetness of SweetenersSaccharin, another artificial sweetener,is marketed as Sweet’N Low.
has been used as a noncarbohydrate artificial sweetener for more than 60 years.has been banned in Canada as an artificial sweetener because studies indicate that it may cause bladder tumors.is still approved by the FDA for use in the United States.
Slide14Study Check
Identify the monosaccharides in each of the following: A. Lactose (1) α-
D-Glucose (2) β-D-Fructose (3) β-D-Galactose B. Maltose (1) α-D-Glucose (2) β-D-Fructose (3) β-D-Galactose C. Sucrose
(1) α-D-Glucose (2) β
-
D
-
Fructose (3) β-D-Galactose
Slide15Solution
Identify the monosaccharides in each of the following: A. Lactose (1) α-
D-Glucose (3) β-D-Galactose B. Maltose (1) α-D-Glucose C. Sucrose (1) α-D-Glucose (2) β-D-Fructose
Slide16Chemistry Link to Health:
Blood Types and CarbohydratesBlood types A, B, AB, and O are determined by terminal saccharides attached to the surface of red blood cells.
Slide17Chemistry Link to Health:
Blood Types and CarbohydratesBlood type O has three common terminal monosaccharides:N-acetylglucosamine,
galactose, and fucose.A contains the same three monosaccharides, but in addition, a molecule of N-acetylgalactosamine is attached to galactose in the saccharide chain.B also contains the same three monosaccharides, but in addition, a second molecule of galactose is attached to the saccharide chain.AB consists of the same monosaccharides found in blood types A and B.
Slide18Chemistry Link to Health:
Blood Types and CarbohydratesThe structures of monosaccharides N-
acetylglucosamine, galactose, and fucose are as follows:
Slide19Chemistry Link to Health:
Blood Types and CarbohydratesPersons with type O blood, which produces antibodies against blood types A, B, and AB, are universal donors.blood types A, B, and AB can receive type O blood.type AB blood, which contains all the terminal monosaccharides
, produce no antibodies to type A, B, or O blood.type AB blood are universal recipients.
Slide20Chemistry Link to Health:
Blood Types and CarbohydratesStructures of these monosaccharides are as follows:
Slide21Chemistry Link to Health:
Blood Types and Carbohydrates
Slide22Chemistry Link to Health:
Blood Types and Carbohydrates
Slide23Study Check
Melibiose is a disaccharide that is 30 times sweeter than sucrose.What are the monosaccharide units in melibiose?What type of
glycosidic bond links the monosaccharides?Identify the structure as α- or β-melibiose.
Slide24Solution
Melibiose is a disaccharide that is 30 times sweeter than sucrose.What are the monosaccharide units in melibiose? α
-D-galactose and α-D-glucoseWhat type of glycosidic bond links the monosaccharides? α-(1 6)-glycosidic bondIdentify the structure as α- or β-melibiose.
α-melibiose