1. Carbohydrates

2. Structure of Carbohydrates

3. Properties of Carbohydrates Most abundant class of organic molecules Source: Photosynthesis Classification –Monosaccharides Stereoisomers Aldehydes (Aldose) or Ketones (Ketose) Number of Carbons (ie 3=triose; 6=hexose) Combined: Aldotriose/Ketotetrose –Polymers Oligosaccharides (2- ~20 sugars) Polysaccharides (> ~20 sugars)

4. Biological Roles of Carbohydrates Energy source Energy storage Cell walls Recognition events –Between proteins (targeting) –Between cells Signalling Components of other biological molecules –Antibiotics –Enzyme cofactors –Nucleic Acids

5. Monosaccharides (Sugars)

6. Classes of Monosaccharides

7. Chirality D- versus L- determined by chirality of highest number carbon (from aldehyde or ketone)

8. Figure 8-1 Aldoses

9. Figure 8-1 Aldoses

10. Figure 8-2 Ketoses

11. Figure 8-2 Ketoses

12. Epimers (stereoisomers differing by configuration of only one of several chiral centers)

14. Enantiomers (mirror images)

15. Mutarotation Creation of new chiral center

16. Formation of Hemiacetal

17. Formation of Hemketal

18. Anomeric Carbon Atom Mutarotation Reversible Creation of new asymmetric center

19. Cyclization of D-Glucose

20. Anomers Anomeric carbon atom –Most oxidized carbon atom –Shares electrons with 2 oxygen atoms  -configuration has -OH on opposite side of ring from CH 2 OH group at chiral center that designates D - or L -

21. Cyclization of D -Fructose (biologically relevant forms)

22. Nomenclature

23. Examples of Nomenclature  - D -glucopyranose  - D -fructofuranose Configuration of anomeric carbon Configuration of sugar Sugar prefix Ring Type *not required Anomeric carbon modification: ose: reducing oside: non-reducing

24. Cyclization of D -Fructose (biologically relevant forms)

25. Figure 8-5 Chair Conformations of  - D -glucopyranose Chair and Boat Forms Equitorial and Axial Substituents Steric Crowding: equitorial more stable EquatorialAxial

26. Derivatives of Monosaccharides

27. Phosphate Esters

28. Deoxy Sugars Note: 5-membered ring form is used in biological systems

29. Amino Sugars (e.g. GlcNAc-6-P)

30. Sugar Alcohols

31. Glycosides

32. Structure of Glycosides

33. Glycosidic Linkages (glycoside) Acetal Stable: no mutarotation Non-reducing sugar (no free anomeric C atom)

34. Nomenclature

35. Reducing test Free Aldehydes are reductants If free to mutarotate sugar is a reductant –Must have only –OH at anomeric carbon Cupric oxide brick-red precipitate Cu 2 O

36. Disaccharides

37. Sucrose (non-reducing) OR: Glc(α1 β2)Fru

38. Sucrose OR: Glc(α1 β2)Fru

39.  -Maltose Glc(α1  4)Glc

40.  -Lactose Gal(β1  4)Glc

41. Nomenclature 1.Recognize individual monosaccharides 2.Drop the –se and add root for rings –6 member: pyran –5 member: furan 3.Attach : –ose: can mutarotate –oside: canNOT mutarotate –osyl: not terminal residu e 4.Indicate carbon to carbon number linkage (#  #) 5.Label each residue with D or L and α or β

42. Oligosaccharides Generally complex –Heteropolymers –Branched Various Cellular Functions –Receptors –Antigens –Signal transduction –Trafficking

43. O-linked Oligosaccharides (serine/threonine)

44. N-linked Oligosaccharides (asparagine)

45. Sugar groups on glycoproteins frequently function in recognition

46. Polysaccharides Simpler structures –Homopolymers –Less branching Limited Cellular Functions –Structural/Protective –Energy Storage

47. Linear Polysaccharides

48. Branched Polysaccharides

49. Functions of Polysaccharides Structural - e.g. plant cell walls, cement between cells (animals):  -linkages stable to enzymatic cleavage Storage - e.g. glycogen as energy reserves:  -linkages are readily cleaved Potential osmotic problem Accessibility for energy production  -linkages Branching

50. Cellulose (plant cell walls)

51. Chitin  (1—>4)-linked homopolymer of N-acetylglucosamine Exoskeletin of invertebrates (e.g. crustacians, insects, and spiders) Cell wall (most fungi and some algae)

52. Glycogen (storage) Linear: α1  4 Branches: α1  6

53. Starch (plants) linear branched (similar to glycogen, but fewer branches)