2. Chapter Eighteen Carbohydrates

3. Ch 18 | # 2 of 52 Carbohydrates cont’d

4. Ch 18 | # 3 of 52 Carbohydrates Major source of ______ from our diet Composed of the elements _, _ and _ Produced by photosynthesis in plants Also called saccharides (sugars)

5. Ch 18 | # 4 of 52 Carbohydrates, Chemically Polyhydroxy aldehydes or polyhydroxy ketones

6. Ch 18 | # 5 of 52 Monosacchrides Three Carbons = ________ Four Carbons = ________ Five Carbons = ________ Six Carbons = ________

7. Ch 18 | # 6 of 52 Monosacchrides Aldoses are monosacchrides with an _________________ group and many hydroxyl (-OH) groups. Ketoses are monosacchrides with a __________________ group and many hydroxyl (-OH) groups.

8. Ch 18 | # 7 of 52 Glucose

9. Ch 18 | # 8 of 52 Galactose D-galactose

10. Ch 18 | # 9 of 52 Fructose

11. Ch 18 | # 10 of 52 Types of Carbohydrates Monosacchrides A carbohydrate that contains a single polyhydroxy aldehyde or polyhydroxy ketone unit. Disaccharides Contain 2 monosacchride units Polysacchrides Contain many monosacchride units

12. Ch 18 | # 11 of 52 Different Forms of Monosaccharides Most monosaccharides exist in two different forms –“left-handed” and –“right-handed” The two forms are related to each other the same way that mirror images are related to each other.

13. Ch 18 | # 12 of 52 ←Fig. 18.3 The mirror image of the right hand is the left hand. Conversely, the mirror image of the left hand is the right hand. Carbohydrates cont’d

14. Ch 18 | # 13 of 52 →Fig. 18.4 A person’s left and right hands are not superimposable upon each other. Carbohydrates cont’d

15. Ch 18 | # 14 of 52 Mirror Images Mirror images –The reflection of an object in a mirror Superimposable mirror images –Images that coincide at all points when the images are laid upon each other Nonsuperimposable mirror images –Images where not all points coincide when the images are laid upon each other The easiest way to determine if two mirror images are superimposable or not, is to make models

16. Ch 18 | # 15 of 52 Chiral Objects Chiral molecules have mirror images that are not superimposable Chiral molecules contain at least one chiral center A chiral carbon atom (“chiral center”) has four different groups attached to it (typically marked with *)

17. Ch 18 | # 16 of 52 Fig. 18.5 Examples of simple molecules that are chiral. Carbohydrates cont’d

18. Ch 18 | # 17 of 52 Stereoisomerism Structural isomers –Isomers in which atoms are connected to each other in different ways Stereoisomers –Isomers whose atoms are connected in the same way but which differ in the orientation of these atoms in space Stereoisomers always have a chiral center and structural rigidity Cis-trans isomers are one form of stereoisomerism

19. Ch 18 | # 18 of 52 Stereoisomers 2 different kinds of stereoisomers –Enantiomers Stereoisomers whose molecules are nonsuperimposable mirror images of each other (the left- and right-hand versions of a single molecule) –Diastereomers Stereoisomers whose molecules are not mirror images of each other

20. Ch 18 | # 19 of 52 →Fig. 18.6 Enantiomers are stereoisomers whose molecules are nonsuperimposable mirror images of each other. a) Enantiomers b) Diastereomers – molecules are not mirror images Carbohydrates cont’d

21. Ch 18 | # 20 of 52 ←Fig. 18.7 The “thought process” used in classifying molecules as enantiomers or diastereomers. Carbohydrates cont’d

22. Ch 18 | # 21 of 52

23. Ch 18 | # 22 of 52 →Fig. 18.8 Emil Fischer was one of the early greats in organic chemistry. He is credited with the development and use of the Fischer Projection Formulas. We have already used this notation in the tetrahedral drawing in a two dimensional form. See page 519 in your text. Carbohydrates cont’d Edgar Fahs Smith Collection, University of Pennsylvania Library

24. Ch 18 | # 23 of 52 Fischer Projections A two-dimensional structural notation for showing the spatial arrangement of groups about chiral centers in molecules –Vertical lines = bonds to groups directed into the page (away from you) –Horizontal lines = bonds to groups directed out of the page (towards you)

25. Ch 18 | # 24 of 52 Properties of Chiral Centers Most important property is a solution of a stereoisomer is its ability to rotate plane polaraized light. Light passing through polarized filters has waves only in one direction, i.e., the light is polarized.

26. Ch 18 | # 25 of 52 ←Fig. 18.9 Vibrational characteristics of ordinary and polarized light. Carbohydrates cont’d

27. Ch 18 | # 26 of 52 Fig. 18.10 Schematic depiction of how a polarimeter works. Carbohydrates cont’d

28. Ch 18 | # 27 of 52 Rotation of light: –Levorotatory: Rotation of light to the left –Dextrorotatory: Rotation of light to the right Not to be confused with D and L forms or the “handedness” of molecules. They are different.

29. Ch 18 | # 28 of 52 D notation

30. Ch 18 | # 29 of 52 Chiral Centers – Why Do We Care? Monosaccharides often contain more than one chiral center –This means that there are at least two different forms of each monosaccharide, a left-handed form and a right- handed form –Each form elicits a different chemical response Biologically active monosaccharides are the right- handed versions of molecules

31. Ch 18 | # 30 of 52 ←Fig. 18.11 The distinctly different natural flavors of spearmint and caraway are caused by enantiomeric molecules. Carbohydrates cont’d

32. Ch 18 | # 31 of 52 Intermolecular Interactions Interactions where there is binding or contact at three points. Look at enantiomeric pair and see how each would bind differently.

33. Ch 18 | # 32 of 52 →Fig. 18.12 Epinephrine binds to the receptor at three points. Carbohydrates cont’d

34. Ch 18 | # 33 of 52

35. Ch 18 | # 34 of 52

36. Ch 18 | # 35 of 52 Cyclic Structures Monosaccharides with 5-6 carbon atoms form cyclic structures The hydroxyl group on C-5 reacts with the aldehyde group or ketone group (to form a hemiacetal or a hemiketal)

37. Ch 18 | # 36 of 52 Haworth Structure for D-Isomers Two-dimensional structural notations that specifies the 3-dimensional structure of a cyclic form of a monosaccharide –The cyclic structure of a D-isomer has the final CH 2 OH group located above the ring.

38. Ch 18 | # 37 of 52 →Fig. 18.16 The cyclic hemiacetal forms of D- glucose result from the intramolecular reaction between the carbonyl group and the hydroxyl group on carbon 5.

39. Ch 18 | # 38 of 52 Haworth Structure for D-Glucose  -D-Glucose  -D-Glucose  

40. Ch 18 | # 39 of 52 ←Fig. 18.17 Walter Norman Haworth was a British carbohydrate chemist. Carbohydrates cont’d © Hulton-Deutsch Collection / CORBIS

41. Ch 18 | # 40 of 52 →Fig. 18.19 The three forms of maltose present in aqueous solution.

42. Ch 18 | # 41 of 52 Disaccharides A disaccharide consists of two monosaccharides Glucose + Glucose  Maltose + water Glucose + Galactose  Lactose + water Glucose + Fructose  Sucrose + water

43. Ch 18 | # 42 of 52

44. Ch 18 | # 43 of 52 ←Fig. 18.22 The polymer chain of a polysaccaride may be unbranched or branched.

45. Ch 18 | # 44 of 52 Amylose, Amylopectin, and Glycogen Amylose is a continuous chain of glucose molecules linked by  -1,4 glycosidic bonds Amylopectin is a branched chain of glucose molecules linked by a  -1,4- and  -1,6-glycosidic bonds. Glycogen is similar to amylopectin, but more highly branched

46. Ch 18 | # 45 of 52 Fig. 18.24 Two perspectives on the structure of the polysaccaride amylopectin.

47. Ch 18 | # 46 of 52 Cellulose Cellulose is a polymer of glucose molecules linked by  -1,4-glycosidic bonds Enzymes in saliva can hydrolyze  -1,4 glycosidic bonds in starch, but not  -1,4 glycosidic bonds in cellulose

48. Ch 18 | # 47 of 52 Carbohydrates cont’d

49. Ch 18 | # 48 of 52 Fig. 18.28 The structures of cellulose (a) chitin (b). Carbohydrates cont’d

50. Ch 18 | # 49 of 52 Phosphate Ester Formation When a cyclic monosaccharide reacts with phosphoric acid, a phosphate ester is produced Phosphodiesters link the monomers in DNA

51. Ch 18 | # 50 of 52 Amino Sugar Formation When a cyclic monosaccharide reacts with an amine, an amine sugar is produced

52. Ch 18 | # 51 of 52 Glycolipids and Glycoproteins A glycolipid is a lipid molecule that has one or more carbohydrate (or carbohydrate derivative) units covalently bonded to it. A glycoprotein is a protein molecule that has one or more carbohydrate (or carbohydrate derivative) units covalently bonded to it.

53. Ch 18 | # 52 of 52