1. 1 carbohydrate The word carbohydrate derives historically from the fact that glucose, has the molecular formula C 6 H 12 O 6 and was originally thought to be a “hydrate of carbon, C 6 (H 2 O) 6.” This view was soon abandoned, but the name survived. 15.1 Carbohydrates Polyhydroxy aldehydes and ketones or substances that hydrolyse to yield polyhydroxy aldehydes and ketones. Carbohydrates can be named by IUPAC rules, but generally common names are used because they are simpler and are universally understood. Sugar saccharide Sugar  combination of Sanskrit words: su (sweet) + gar (sand)  “sweet sand” The Latin word for sugar is saccharum, and the derived name saccharide is the basis of a system of carbohydrate classification.

2. 2 Types of carbohydrates Simple carbohydrate = simple sugars = are monosaccharides.They are all sweet Complex carbohydrates = complex sugars = are made of two or more simple sugars. Oligosaccharidesoligo = few “dextrins” Hydrolysis = breakdown with water

3. 3 15.2 Fischer Projections of Monosaccharides Places the most oxidized group at the top. chiral Shows chiral carbons as the intersection of vertical and horizontal lines. The −OH group on the chiral carbon farthest from the carbonyl group determines an L or D isomer. Left is assigned the letter L for the L-isomer. Right is assigned the letter D for the D-isomer. Latin Levo = left Dextro = right Emil Fischer determined the structure of glucose in 1900 and won the Noble Prize in Chemistry in 1902 A chiral carbon is bonded to 4 distinct groups and posses a special property, they are not superimposable with their mirror image. Enantiomers Stereoisomers which are non-superimposable with their mirror image.

4. 4 D-fructose ketohexose Is a ketohexose C 6 H 12 O 6 Is the sweetest carbohydrate. Is found in fruit juices and honey. Converts to glucose in the body. D-galactose Is an aldohexose C 6 H 12 O 6 Not found free in nature. Obtained from lactose, a disaccharide. A similar structure to glucose except for the –OH on C4. Isomers D-glucose aldohexose is an aldohexose C 6 H 12 O 6 Found in fruits, corn syrup, and honey. Known as dextrose, grape sugar, and blood sugar. The monosaccharide in polymers of starch, cellulose, and glycogen.

5. 5 Aldoses

6. 6 A ketose has one fewer asymmetric center than an aldose. Therefore, ketoses have fewer stereoisomers than aldoses. ketoses have the ketone group in the 2-position.Naturally occurring ketoses have the ketone group in the 2-position. Ketoses

7. 7 Aldehydes and ketones can react with an alcohol to form a hemiacetal. 15.3 Cyclic Structures of Monosaccharides (Haworth Structures) Cyclic hemiacetals form when the C=O group and the —OH are part of the same molecule. C-5For hexoses, the hydroxyl group on C-5 reacts with the aldehyde group or ketone group. Are the prevalent form of monosaccharides with 5 or 6 carbon atoms. English chemist Sir Norman Haworth Leads to an equatorial-equatorial configuration referred to as the beta ( β ) isomer. A special type of stereoisomer called an anomer. Leads to an equatorial-axial configuration referred to as the alpha ( α ) isomer. An anomer is one of two stereoisomers of a cyclic saccharide that differs only in its configuration at the hemiacetal carbon, also called the anomeric carbon. Put simply, the anomeric carbon is the carbonyl carbon.

8. 8

9. D-glucose 9

10. 10 D-Glucose exists in three different forms: anomer

11. 15.4 Chemical Properties of Monosaccharides Oxidation [O] [O] Aldehydes  carboxylic acid Aldoses have an aldehyde group :. Reducing sugars In aq. solution ketoses slowly rearrange to aldoses :. react Ketoses rearrange to an aldehyde group :. Reducing sugars 11

12. The oxidizing agent is Cu 2+ The oxidizing agent, itself is reduced: Cu 2+ + e-  Cu + 12 Benedict’s reagent Oxidation by Benedict’s reagent

13. 13 Tollens reagent reacts with aldehyde, but the base present in the solution, promotes rearrangements, so ketoses react too. Sugars that give a silver mirror with Tollens are called reducing sugars. The oxidizing agent is Ag+ The oxidizing agent, itself is reduced: Ag+ + e-  Ag Tollens Reagent Oxidation by Tollens Reagent

14. [H] [H] Reduction ReductionAldehydes  1˚ alcohols sugar alcohols alditolsProduces sugar alcohols called alditols. Such as D-glucose gives D- glucitol also called sorbitol. Sorbitol is about 60 percent as sweet as sucrose with one-third fewer calories and may be useful to people with diabetes. Sorbitol has been safely used in processed foods for almost half a century. 14

15. Sugars and artificial sweeteners 15

16. 15.5 Disaccharides Because cyclic sugars are hemiacetals, they can react with an alcohol to form the carbohydrate equivalent of an acetal, which is called a glycoside. Therefore, 2 monosaccharides can react, one as a hemiacetal and the other as an alcohol to give the equivalent glycoside. 16

17. In naming glycosidic bonds, it is necessary to name the configuration as well as the carbons involved in the bond formation. If the –OH group had been in the beta configuration when the glycosidic bond was formed, the bond would be in the β(1→4) configuration. The molecule formed would be named cellobiose and would have a different two-dimensional and three-dimensional shape than maltose. 17

18. 18 The three forms of maltose present in aqueous solution. β

19. Sucrose Sucrose is known as table sugar. It is the most abundant disaccharide found in nature. Sucrose is found in sugar cane and sugar beets. Both anomeric carbons of the monosaccharides in sucrose are bonded, therefore, sucrose is not a reducing sugar. It will not react with Benedict’s reagent. Glycosidic bond between C-1 of glucose (in the  -position) And C-2 of fructose (in the β -position) The designation here is different since two anomeric Cs are involved in the glycosidic linkage. 19

20. 20 What you need to know Monosaccharides Disaccharide Glucose + glucose  maltose + H 2 O  (1  4) Glucose + galactose  lactose + H 2 O β(1  4) Glucose + fructose  sucrose + H 2 O ,β(1  2) AldohexosesGlucose  3 Galactose  3, 4 Ketohexosesfructose Ribose deoxyribose

21. 21 15.6 Polysaccharides Cellulose and starch Cellulose and starch are the two most widely occurring polysaccharides. Different cellulose molecules interact to form a large aggregate structure held together by hydrogen bonds. Nature uses cellulose as a structural material to impart strength and rigidity to plants. Leaves, grasses, and cotton are primarily cellulose.

22. 22 Starch Starch can be separated into 2 fractions: Potatoes, corn, and cereal grains contain large amounts of starch.

23. Storage polysaccharides Starch (in plants) Glycogen (in animals) Amylose Amylose ~ 20% by weight of starch linear glucose polymer several 100’s (up to ~4,000), α (1  4) more branched and compact than amylopectin. α (1  4)glucose polymer with α (1  6) linked branches Amylopectin Amylopectin ~ 80% by weight of starch branched glucose polymer several 1000’s (up to ~10,000), α (1  4) and α (1  6) 23 Total amount in human body ~ 350g divided ~equally in liver and muscle The small, dense particles (blue) within this electron micrograph of a liver cell are glycogen granules.

24.  Cellulose: glucose polymer made up of 1,4’-  -glycoside linkages  Amylose: glucose polymer made up of 1,4’-  -glycoside linkages Difference 24

25. 25 Different glycosidic linkages in starch and cellulose  different physical properties.     Linkages in starch amylose  amylose has an   helix that promotes H-bonding to water  starch is soluble in water β β Linkages in cellulose  promotes extensive intramolecular H-bonding forming linear arrays  Insoluble in water Amylose nor amylopectin is truly soluble in water, too big to form a true solution, they form dispersions.

26. Cellulose The linear nature of the molecules allows them to act like stiff rods, a feature that enables then to align side by side into well organized water insoluble fibers. There are not enough water molecules on the surface of the fiber to pull individual molecules apart, extensive H-bonds. 26

27. Cellulose Cellulose is an insoluble fiber in our diet because we lack the enzyme cellulase to hydrolyze the  (1→4) glycosidic bond. Whole grains are a good source of cellulose. Cellulose is important in our diet because it assists with digestive movement in the small and large intestine. Some animals and insects can digest cellulose because they contain bacteria that produce cellulase. 27

28. 28 Use of iodine to test for starch. Blue liq. = I 2 in presence of starch Clear liq.= solution of I2

29. 1. What functional group(s) is in the open chains of monosaccharides? a. hydroxyl groupsb. aldehyde groups or ketone groupsc. ketone groupsd. answers 1 and 2 2. What is the classification of the following sugar? a. aldotrioseb. aldopentosec. ketotetrosed. ketohexose 3. What is the classification of the following sugar? a. aldotrioseb. ketopentosec. aldotetrosed. ketotetrose 4. What are the functional groups and the number of -OH groups in an aldohexose? a. aldehyde and four -OH groupsb. aldehyde and five -OH groups c. ketone and five -OH groupsd. ketone and four -OH groups 29 Ch#15-Extra CreditDue right at the end of the chapter.

30. 5. Structure A and B are shown below. Determine whether each structure is the D or L isomer. a. Structure A is an L-isomer and Structure B is an L-isomer. b. Structure A is a D-isomer and Structure B is a D-isomer. c. Structure A is a D-isomer and Structure B is an L-isomer. d. Structure A is an L-isomer and Structure B is a D-isomer. 6. Which carbohydrate is this? a. D-glucoseb. L-glucose c. D-ribosed. L-ribose 7. This carbohydrate has how many chiral carbons and has which D/L orientation? a. Three chiral carbons and an L-orientationb. five chiral carbons and an L-orientation c. five chiral carbons and a D-orientationd. Three chiral carbons and a D-orientation 9. Which monosaccharide is also known as dextrose or blood sugar? a. Glucoseb. ribosec. galactosed. fructose 8. Which monosaccharide is also known as fruit sugar? a. riboseb. galactosec. glucosed. fructose 30

31. 31 A B 11. Which of the following is the correct Haworth structure for D-mannose? A B C D E

32. 12. When glucose is treated with Benedict's solution, blue Cu 2+ ions are reduced and a red precipitate forms. What changes occur to the glucose molecule? The terminal alcohol group is oxidized to a carboxylic acid. The last chiral alcohol group is oxidized to a ketone. The ketone group is reduced to an alcohol. The aldehyde group is oxidized to a carboxylic acid. 13. What structural change occurs when glucose is treated with H 2 ? The ketone group is reduced to an alcohol. The aldehyde group is reduced to an alcohol. The terminal alcohol group is oxidized to a carboxylic acid. The last chiral alcohol group is reduced to a alkane. 14. What transformation is happening in this reaction? the reduction of D-galactose the oxidation of L-galactose the oxidation of D-galactose the reduction of L-galactose 15. What transformation is happening in this reaction? the oxidation of L-mannose the reduction of L-mannose the reduction of D-mannose the oxidation of D-mannose 32

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34. 19. Melibiose is a disaccharide that is 30 times sweeter than sucrose. 34 a. What are the monosaccharide units in melibiose? b. What type of glycosidic bond links the monosaccharides? c. Identify the structure as α- or β-melibiose.

35. 20. Animal starch that is stored in the liver and muscles is which polysaccharide? cellulose sucrose glycogen amylose 21. What is the monosaccharide used to build polysaccharides of amylopectin? glucose galactose Lactose amylose 22. Which disaccharide occurs as a breakdown product of amylose? Sucrose Maltose Glycogen amylopectin 35