In The Name of Allah

1. In The Name of Allah

2. Dr. Ali Moradi Shaid-sadoughi University Biochemistry Department

3. References • LubertStryer - Biochemistry • Lehninger- Principles of Biochemistry • Harper's -Illustrated Biochemistry • Text Book of Biochemistry with clinical correlation, T M. Devlin • بیوشیمی پزشکی، هیئت مولفان ، دانشگاه علوم پزشکی تهران، انتشارات آییژ، دو جلد

4. Carbohydrates

5. General characteristics Compounds composed of C, H, and O (CH2O)n when n = 5 then C5H10O5 Not all carbohydrates have this empirical formula: Deoxysugars, Aminosugars Carbohydrates are the most abundant compounds found in nature (cellulose: 100 billion tons annually)

6. General characteristics Most carbohydrates are found naturally in bound form rather than as simple sugars (Glycoconjugates) Polysaccharides (starch, cellulose, inulin, gums), Mucopolysaccharides (hyaluronic acid) Glycoproteins and proteoglycans (hormones, blood group substances, antibodies) Glycolipids (cerebrosides, gangliosides) Nucleic acids (Ribose and desoxyribose)

7. Functions Sources of energy (Glucose, Fructose,..) Intermediates in the biosynthesis of other basic biochemical entities (Fats and proteins) Form structural tissuesin plants and in microorganisms (cellulose, lignin, murein) Participate in cell-cell recognition, Cell-cell adhesion

8. Classification of carbohydrates Monosaccharides(monoses or glycoses) Oligosaccharides(condensation products of two to ten monosaccharides) Di, tri, tetra, penta, up to 9 or 10 Most important are the disaccharides Polysaccharides or glycans(more than 10) Homopolysaccharides Heteropolysaccharides

9. Classification of Monosaccharides • Number of carbons in chain • Trioses (3C) • tetroses (4C) • pentoses (5C) • hexoses (6C) • heptoses (7C) • Aldose or Ketose • Aldoses (e.g., glucose) have an aldehyde group at one end • Ketoses (e.g., fructose) have a keto group, usually at C2

10. Aldose sugars

12. Ketose sugars

14. Sugars Exhibit Various Forms of Isomerism

15. Aldose and Ketose isomers

16. L and D Isomers D Form: Most of the monosaccharides occurring in mammals are D sugars, and the enzymes responsible for their metabolism are specific for this configuration. L-arabinose L-idoronic acid L form:

17. Enantiomers

18. Epimers Two sugars that differ only in the configuration around one carbon atom are called epimers;

19. Optical isomerism Asymmetric compounds rotate plane polarized light • In general, a molecule with n chiralcenters can have 2n stereoisomers • Of the 16 possible aldohexoses, eight are D forms and eight are L • Most of the hexoses of living organisms are D isomers.

20. POLARIMETRY Measurement of optical activity in chiralor asymmetric molecules using plane polarized light Measurement uses an instrument called a polarimeter (Lippich type) Rotation is either (+) dextrorotatory or (-) levorotatory

23. polarimetry Magnitude of rotation depends upon: 1. The nature of the compound 2. The length of the tube (cell or sample container) usually expressed in decimeters (dm) 3. The wavelength of the light source employed; usually either sodium line at 589.3 nm or mercury vapor lamp at 546.1 nm 4. Temperature of sample 5. Concentration of analyte in grams per 100 ml

24. Polarimetry D = Na+ line T = temperature oC a obs : observed rotation in degree (specify solvent) l = length of tube in decimeter c = concentration in grams/100ml [a] = specific rotation

25. Specific rotation of various carbohydrates at 20oC D-glucose +52.7 D-fructose -92.4 D-galactose +80.2 L-arabinose +104.5 D-mannose +14.2 D-arabinose -105.0 D-xylose +18.8 Lactose +55.4 Sucrose +66.5 Maltose+ +130.4 Invert sugar -19.8 Dextrin +195

26. Racemic mixture • In chemistry, a racemic mixture, or racemate, is one that has equal amounts of left- and right-handed enantiomers of a chiral molecule. • A racemic mixture is denoted by the prefix (±)- or dl- (for sugars the prefix dl- may be used), indicating an equal (1:1) mixture of dextro and levo isomers • A racemate is optically inactive

27. Tartaric acid • It occurs naturally in many plants, particularly grapes, bananas • Add to foods to give a sour taste • Used as an antioxidant

28. Structural representation of sugars Fisher projection: straight chain representation Haworth projection: simple ring in perspective Conformational representation: chair and boat configurations

29. Rules for drawing Haworth projections draw either a six or 5-membered ring including oxygen as one atom most aldohexoses are six-membered Aldotetroses, Aldopentoses, ketohexoses are five-membered Furan Pyran

30. Rules for drawing Haworth projections Next number the ring clockwise starting next to the oxygen If the substituent is to the right in the Fisher projection, it will be drawn down in the Haworth projection (Down-Right Rule)

31. Rules for drawing Haworth projections For D-sugarsthe highest numbered carbon (furthest from the carbonyl) is drawn up. For L-sugars, it is drawn down For D-sugars, the OH group at the anomeric position is drawn down for αand up for β. For L-sugarsα is up and β is down

32. Formation of the two cyclic forms of D-glucose Anomers: Isomeric forms of monosaccharides that differ only in the configuration about the hemiacetal or hemiketal carbon atom are called Mutarotation: interconvert of The a and b anomes of D-glucose in aqueous solution <1% Conformations: interconvertible without the breakage of covalent bonds, configurations : interconvertible only by breaking a covalent bond—for example, in the case of α and β configurations, one-third two-thirds

33. Condensation reactions: acetal and ketal formation

34. D-ribose and other five-carbon saccharides can form either furanose or pyranose structures

35. Chair and boat conformations of a pyranose sugar 2 possible chair conformations of b-D-glucose

36. Envelope Conformations of β- D-ribose Envelope Conformations

37. Oxidation reactions Aldoses may be oxidized to 3 types of acids Aldonic acids: aldehyde group is converted to a carboxyl group ( glucose – gluconic acid) Uronic acids: aldehyde is left intact and primary alcohol at the other end is oxidized to COOH Glucose --- glucuronic acid Galactose --- galacturonic acid Saccharic acids: (glycaric acids) – oxidation at both ends of monosaccharide) Glucose ---- saccharic acid Galactose --- mucic acid Mannose --- mannaric acid

39. Solutions of cupric ion (known as Fehling's solution) provide a simple test for sugars such as glucose. Sugars that react are called reducing sugars; those that do not are called nonreducing sugars

41. Reduction either done catalytically (hydrogen and a catalyst) or enzymatically the resultant product is a polyol or sugar alcohol (alditol) glucose form sorbitol (glucitol) mannose forms mannitol fructose forms a mixture of sorbitol glyceraldehyde gives glycerol

42. Sructures of some sugar alcohols

43. used as a sugar substitute in foods, especially for diabetics. In cosmetics it is commonly used in aftershave lotions, mild soaps and baby shampoos. Sorbitol is used as a humectant and skin conditioning agent

44. Special monosaccharides: deoxy sugars These are monosaccharides which lack one or more hydroxyl groups on the molecule one quite ubiquitous deoxy sugar is 2’-deoxy ribose which is the sugar found in DNA 6-deoxy-L-mannose (L-rhamnose) is used as a fermentative reagent in bacteriology

45. examples of deoxysugars

46. Several sugar esters important in metabolism

47. Special monosaccharides: amino sugars Constituents of mucopolysaccharides

49. The anomeric forms of methyl-D-glucoside