1. 20 20-1 © 2006 Thomson Learning, Inc. All rights reserved Chair Conformations chair conformation For pyranoses, the six-membered ring is more accurately represented as a chair conformation.

2. 20 20-2 © 2006 Thomson Learning, Inc. All rights reserved Chair Conformations In both Haworth projections and chair conformations, the orientations of groups on carbons 1- 5 of  -D- glucopyranose are up, down, up, down, and up.

3. 20 20-3 © 2006 Thomson Learning, Inc. All rights reserved Mutarotation Mutarotation: Mutarotation: the change in specific rotation that accompanies the equilibration of  - and  - anomers in aqueous solution. Example: when either  -D-glucose or  -D-glucose is dissolved in water, the specific rotation of the solution gradually changes to an equilibrium value of +52.7°, which corresponds to 64% beta and 36% alpha forms.

4. 20 20-4 © 2006 Thomson Learning, Inc. All rights reserved Physical Properties Monosaccharides are colorless crystalline solids, very soluble in water, but only slightly soluble in ethanol Sweetness relative to sucrose:

5. 20 20-5 © 2006 Thomson Learning, Inc. All rights reserved Formation of Glycosides Treatment of a monosaccharide, all of which exist almost exclusively in cyclic hemiacetal forms, with an alcohol gives an acetal. Acetals α + β Mutarotation = No Hemiacetal mutarotation =Yes yes no

6. 20 20-6 © 2006 Thomson Learning, Inc. All rights reserved Formation of Glycosides glycosideA cyclic acetal derived from a monosaccharide is called a glycoside. glycosidic bondThe bond from the anomeric carbon to the -OR group is called a glycosidic bond. Mutarotation is not possible in a glycoside because an acetal, unlike a hemiacetal, is not in equilibrium with the open-chain carbonyl-containing compound. Glycosides are stable in water and aqueous base, but like other acetals, are hydrolyzed in aqueous acid to an alcohol and a monosaccharide. Glycosides are named by listing the alkyl or aryl group bonded to oxygen followed by the name e-ide of the carbohydrate in which the ending -e is replaced by -ide.

7. 20 20-7 © 2006 Thomson Learning, Inc. All rights reserved Reduction to Alditols The carbonyl group of a monosaccharide can be reduced to an hydroxyl group by a variety of reducing agents, including NaBH 4 and H 2 in the presence of a transition metal catalyst. alditolThe reduction product is called an alditol. alditol

8. 20 20-8 © 2006 Thomson Learning, Inc. All rights reserved Reduction to Alditols Sorbitol is found in the plant world in many berries and in cherries, plums, pears, apples, seaweed, and algae. It is about 60 percent as sweet as sucrose (table sugar) and is used in the manufacture of gums, candies and as a sugar substitute for diabetics. These four alditols are also common in the biological world.

9. 20 20-9 © 2006 Thomson Learning, Inc. All rights reserved Oxidation to Aldonic Acids The aldehyde group of an aldose is oxidized under basic conditions to a carboxylate anion. aldonic acidThe oxidation product is called an aldonic acid. reducing sugarA carbohydrate that reacts with an oxidizing agent to form an aldonic acid is classified as a reducing sugar (it reduces the oxidizing agent). enediol intermed.

10. 20 20-10 © 2006 Thomson Learning, Inc. All rights reserved Oxidation to Uronic Acids uronic acid Enzyme-catalyzed oxidation of the primary alcohol at C-6 of a hexose yields a uronic acid. Fisher proj. Chair conformation e.g. Enzyme-catalyzed oxidation of D-glucose, yields D-glucuronic acid.

11. 20 20-11 © 2006 Thomson Learning, Inc. All rights reserved D-Glucuronic Acid D-Glucuronic acid is widely distributed in the plant and animal world. In humans, it is an important component of the acidic polysaccharides of connective tissues, e.g. collagen. Used by the body to detoxify foreign phenols and alcohols; in the liver, compounds  converted to glycosides of glucuronic acid and excreted in the urine.

12. 20 20-12 © 2006 Thomson Learning, Inc. All rights reserved Two Volunteers needed... 1 male 1 female

13. 20 20-13 © 2006 Thomson Learning, Inc. All rights reserved Testing for Glucose

14. 20 20-14 © 2006 Thomson Learning, Inc. All rights reserved Phosphate Esters Mono- and diphosphoric esters are intermediates in the metabolism of monosaccharides. For example, the first step in glycolysis is conversion of D-glucose to a-D-glucose 6-phosphate. Note that at the pH of cellular and intercellular fluids, both acidic protons of a diphosphoric ester are ionized, giving it a charge of -2.

15. 20 20-15 © 2006 Thomson Learning, Inc. All rights reserved Disaccharides e.g. Sucrose (table sugar) Sucrose is the most abundant disaccharide in the biological world; it is obtained principally from the juice of sugar cane and sugar beets. Sucrose is a nonreducing sugar.

16. 20 20-16 © 2006 Thomson Learning, Inc. All rights reservedDisaccharides Lactose Lactose sugar present in milk; 5-8% human milk, 4-6% cow's milk. Little sweetness: added to cheap foods ~ fillers... D-galactopyranose bonded by a b-1,4-glycosidic bond to carbon 4 of D-glucopyranose. Lactose is a reducing sugar. Why? In equilb. w/ Open chain form~ can be oxidized to carboxylate

17. 20 20-17 © 2006 Thomson Learning, Inc. All rights reserved A, B, AB and O Blood types

18. 20 20-18 © 2006 Thomson Learning, Inc. All rights reserved Antigen Anti-bodies

19. 20 20-19 © 2006 Thomson Learning, Inc. All rights reserved Disaccharides Maltose Present in malt, the juice from sprouted barley and other cereal grains. Maltose consists of two units of D-glucopyranose joined by an  -1,4-glycosidic bond. Maltose is a reducing sugar.

20. 20 20-20 © 2006 Thomson Learning, Inc. All rights reserved Polysaccharides Polysaccharide: Polysaccharide: a carbohydrate of many monosaccharides joined by glycosidic bonds. Starch: Starch: a polymer of D-glucose, E stores in plants Two forms: amylose and amylopectin. 25% Amylose, unbranched chains w/ 4000 D-glucose units joined by  -1,4-glycosidic bonds. 75% Amylopectin, has branched chains with up to 10,000 D-glucoses, joined by  -1,4-glycosidic bonds; at branch points, new chains of 24 to 30 units are started by  -1,6- glycosidic bonds.

21. 20 20-21 © 2006 Thomson Learning, Inc. All rights reserved Polysaccharides Figure 20.3 Amylopectin.

22. 20 20-22 © 2006 Thomson Learning, Inc. All rights reserved Polysaccharides Glycogen Glycogen is the energy-reserve carbohydrate for animals. Glycogen is a branched polysaccharide of approximately 10 6 glucose units joined by  -1,4- and  - 1,6-glycosidic bonds. The total amount of glycogen in the body of a well- nourished adult human is about 350 g, divided almost equally between liver and muscle.

23. 20 20-23 © 2006 Thomson Learning, Inc. All rights reserved Polysaccharides Cellulose Cellulose linear polysaccharide - D-glucose units,  -1,4-glycosidic bonds. ~ molecular weight of 400,000 g/mol, corresponding to approximately 2200 glucose units per molecule. Cellulose align themselves side by side into fibers.. OH groups form numerous intermolecular H-bonds. This arrangement of parallel chains in bundles gives cellulose fibers their high mechanical strength. reason why cellulose is insoluble in water.

24. 20 20-24 © 2006 Thomson Learning, Inc. All rights reserved Polysaccharides Cellulose (cont’d) Humans can’t use cellulose, lack digestive enzymes  -glucosidases, catalyze hydrolysis of  -glucosidic bonds. Humans have only  -glucosidases; hence, the polysaccharides we use as sources of glucose are starch and glycogen. Many bacteria and microorganisms have  -glucosidases and can digest cellulose. Termites have such bacteria in their intestines and can use wood as their principal food. Ruminants (cud-chewing animals) and horses can also digest grasses and hay.

25. 20 20-25 © 2006 Thomson Learning, Inc. All rights reserved Acidic Polysaccharides Acidic polysaccharides: Acidic polysaccharides: a group of polysaccharides that contain carboxyl groups and/or sulfuric ester groups, and play important roles in the structure and function of connective tissues. There is no single general type of connective tissue. Large number of highly specialized forms, such as cartilage, bone, synovial fluid, skin, tendons, blood vessels, intervertebral disks, and cornea. Most connective tissues are made up of collagen, a structural protein, in combination with a variety of acidic polysaccharides.

26. 20 20-26 © 2006 Thomson Learning, Inc. All rights reserved Acidic Polysaccharides e.g. Hyaluronic acid e.g. Hyaluronic acid contains from 300 to 100,000 repeating units. is most abundant in embryonic tissues, connective tissues (synovial fluid) the lubricant of joints -the vitreous of the eye: provides a clear, elastic gel that maintains the retina in its proper position

27. 20 20-27 © 2006 Thomson Learning, Inc. All rights reserved Acidic Polysaccharides Heparin Heparin: a heterogeneous mixture of variably sulfonated polysaccharide chains, ranging in molecular weight from 6,000 to 30,000 g/mol.

28. 20 20-28 © 2006 Thomson Learning, Inc. All rights reserved Acidic Polysaccharides Heparin (cont’d) Heparin is synthesized and stored in mast cells of various tissues, particularly the liver, lungs, and gut. The best known and understood of its biological functions is its anticoagulant activity (blood thinner). It binds strongly to antithrombin III, a plasma protein involved in terminating the clotting process.