1. Carbohydrates 2/9/2016Dr Seemal Jelani Introduction to Biochemistry1

2. Most abundant  Their abundance in human body is low but constitute about 75% by mass of dry plant materials  Green (chlorophyll-containing) plants produce carbohydrates via photosynthesis  A major source of energy from our diet composed of the elements C, H and O.  They also called saccharides, which means “sugars.” 2/9/2016 Dr Seemal Jelani Introduction to Biochemistry 2 Carbohydrates

3.  They are produced by photosynthesis in plants.  such as glucose are synthesized in plants from CO 2 from the air, H 2 O from the soil, and energy from the sun absorbed in chlorophyll to form carbohydrates and O2  Oxidized in living cells to produce CO 2, H 2 O, and energy. 2/9/2016 Dr Seemal Jelani Introduction to Biochemistry 3

4.  Cellulose (carbohydrates) serve as structural elements  Starch (carbohydrates) provide energy reserves for the plants 2/9/2016 Dr Seemal Jelani Introduction to Biochemistry 4 Uses of carbohydrates in plants

5.  Dietary intake of plant materials is the major carbohydrate source for humans and animals  Functions:  Carbohydrate oxidation provides energy  Carbohydrate storage in the form of glycogen provides a short-term energy reserve  Carbohydrates supply carbon atoms for the synthesis of other biochemical substances (proteins, lipids, nucleic acids)  Carbohydrate form part of the structural framework of DNA and RNA 2/9/2016 Dr Seemal Jelani Introduction to Biochemistry 5

6. Classification of Carbohydrates The types of carbohydrates are Monosaccharides, the simplest carbohydrates. Disaccharides, which consist of two monosaccharides. Polysaccharides, which contain many monosaccharides. 2/9/2016 Dr Seemal Jelani Introduction to Biochemistry 6

7.  C n H 2n O n  Carbohydrates are Polyhydroxy aldehydes, Polyhydroxy ketones  The carbohydrate glucose is Polyhydroxy aldehyde and the carbohydrate fructose is Polyhydroxy ketone 2/9/2016 Dr Seemal Jelani Introduction to Biochemistry 7 General Formula

8. CHIRALITY: Handedness in molecules  A chiral object is not superimposable on its mirror image they do not possess a plane of symmetry  Two forms of a chiral object are known as enantiomers 2/9/2016dr seemal jelani8

9. Mirror image 2/9/2016dr seemal jelani9

10. Mirror image 2/9/2016dr seemal jelani10

11. Non superposable 2/9/2016dr seemal jelani11

12. Chiral HANDS 2/9/2016dr seemal jelani12

13. Chiral Shells 2/9/2016dr seemal jelani13

14. The plane has the same thing on both sides for the flask There is no mirror plane for a hand 2/9/2016dr seemal jelani14

15.  If an object has a plane of symmetry it is necessarily the same as its mirror image  The lack of a plane of symmetry is called “handedness”, Chirality 2/9/2016dr seemal jelani15

16.  Hands, gloves are prime examples of chiral object  They have a “left” and a “right” version 2/9/2016dr seemal jelani16

17. Why this chapter?  Handedness is important in organic and biochemistry  Molecular handedness makes possible specific interactions between enzymes and substrates 2/9/2016dr seemal jelani17

18. Chirality in daily life  Most Biomolecules in nature are chiral (sugars, DNA, proteins, amino acids, steroids)  Human proteins are exclusively built from L-amino acids; this involves receptors which are chiral 2/9/2016dr seemal jelani18

19.  Aldehydes CHO Aldose  Ketone C=O Ketose Functional groups in carbohydrates 2/9/2016 Dr Seemal Jelani Introduction to Biochemistry 19

20.  Carbohydrates may contain more than one chiral center  FP represents a method for giving molecularity specifications in two dimensions  FP is a two dimensional notation for showing the spatial arrangement of groups about chiral centers in molecule Chirality in carbohydrates Fischer projections 2/9/2016 Dr Seemal Jelani Introduction to Biochemistry 20

21.  Stereoisomers  Enantiomers  Diastereomers  Handedness (Right and left)  D and L  Fischer Projection for 2,3,4-trihydroxybutanal  Epimers 2/9/2016 Dr Seemal Jelani Introduction to Biochemistry 21

22.  Structural isomers have different properties  Diastereoisomers have different properties  Enantiomers have same properties expect two:  Their interaction with plane polarized light  Their interaction with other chiral substances Properties of Enantiomers 2/9/2016 Dr Seemal Jelani Introduction to Biochemistry 22

23.  Isomers whose atoms are connected in the same way but differ in their arrangement in space  The two non superimposable mirror-image forms of a chiral molecule are stereoisomers Stereoisomers 2/9/2016 Dr Seemal Jelani Introduction to Biochemistry 23

24.  Two major causes:  The presence of a chiral center in a molecule  The presence of structural rigidity in a molecule  The structural rigidity is caused by restricted rotation about chemical bonds Causes of stereoisomerism 2/9/2016 Dr Seemal Jelani Introduction to Biochemistry 24

25. 2/9/2016Dr Seemal Jelani Chem-24125 P LANE -P OLARIZED L IGHT Polarimeter: Polarimeter: a device for measuring the extent of rotation of plane-polarized light

26. Plane-Polarized Light Light Light vibrating in all planes  to direction of propagation Plane-polarized light: Plane-polarized light: light vibrating only in parallel planes optical activity Plane-polarized light the vector sum of left and right circularly polarized light

27. Enantiomers (chiral) interact with Optically Activity Enantiomers (chiral) interact with circularly polarized light rotating the plane one way with R center and opposite way with S result: rotation of plane-polarized light clockwise (+) or counterclockwise (-)

28. Change in the polarized plane? no change in the plane achiral sample Plane-Polarized Light (polarimeter)

29. rotates the plane  Plane-Polarized Light (polarimeter) Change in the polarized plane?

30. Monosaccharides consist of  3-6 carbon atoms typically.  A carbonyl group (aldehyde or ketone).  Several hydroxyl groups.  2 types of monosaccharide structures: Aldoses and ketoses 2/9/2016 Dr Seemal Jelani Introduction to Biochemistry 30 Classification of Monosaccharides

31. Aldoses are monosaccharides  with an aldehyde group  with many hydroxyl (-OH) groups. triose (3C atoms) tetrose (4C atoms) pentose (5 C atoms) hexose (6 C atoms) 2/9/2016 Dr Seemal Jelani Introduction to Biochemistry 31 Aldoses O ║ C─H aldose │ H─ C─OH │ H─ C─OH │ CH 2 OH Erythose, an Aldotetrose

32. Ketoses are monosaccharides  with a ketone group  with many hydroxyl (-OH) groups. 2/9/2016 Dr Seemal Jelani Introduction to Biochemistry 32 Ketoses CH 2 OH │ C=O ketose │ H─ C─OH │ H─ C─OH │ H─C─OH │ CH 2 OH Fructose, a ketohexose

33. 2/9/2016 Dr Seemal Jelani Introduction to Biochemistry 33

34. Learning Check Identify each as aldo- or keto- and as tetrose, pentose, or hexose: 2/9/2016 Dr Seemal Jelani Introduction to Biochemistry 34

35. Structures of Monosaccharides 2/9/2016 Dr Seemal Jelani Introduction to Biochemistry 35 Copyright © 2005 by Pearson Education, Inc. Publishing as Benjamin Cummings

36. A Fischer projection  is used to represent carbohydrates.  places the most oxidized group at the top.  shows chiral carbons as the intersection of vertical and horizontal lines. 2/9/2016 Dr Seemal Jelani Introduction to Biochemistry 36 Fischer Projections

37.  CH 3 CHOHC 6 H 5 2/9/2016 Dr Seemal Jelani Introduction to Biochemistry 37 Learning check

38. In a Fischer projection, 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-form.  right is assigned the letter D for the D-form. 2/9/2016 Dr Seemal Jelani Introduction to Biochemistry 38 D and L Notations

39. LC of D and L Isomers of Monosaccharides 2/9/2016 Dr Seemal Jelani Introduction to Biochemistry 39 glucose ribose galactose

40.  found in fruits, corn syrup, and honey.  an aldohexose with the formula C 6 H 12 O 6 known as blood sugar in the body.  The monosaccharide in polymers of starch, cellulose, and glycogen. 2/9/2016 Dr Seemal Jelani Introduction to Biochemistry 40 D-Glucose

41. D-Fructose  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. 2/9/2016 Dr Seemal Jelani Introduction to Biochemistry 41

42. Cyclic structures  are the widespread form of monosaccharides with 5 or 6 carbon atoms. 2/9/2016 Dr Seemal Jelani Introduction to Biochemistry 42 Cyclic Structures

43.  The cyclic forms of monosaccharides result from the ability of their carbonyl group to react intramolecularly with a –OH group  Cyclic structure is formed when the –OH group on C-5 reacts with the aldehyde group or ketone group  The result is a cyclic hemiacetal or cyclic hemiketal 2/9/2016 Dr Seemal Jelani Introduction to Biochemistry 43

44. LE 5-4 Abbreviated ring structure

45. Steps for cyclisation for D-Glucose  All –OH groups to the right in the projection formula appear below the ring whereas –OH gps to the left in FP appear above the ring 2/9/2016 Dr Seemal Jelani Introduction to Biochemistry 45

46. Drawing the Cyclic Structure for Glucose Number the carbon chain and turn clockwise to form a linear open chain. 2/9/2016 Dr Seemal Jelani Introduction to Biochemistry 46 123456123456 6 5 4 3 2 1

47. Cyclic Structure for Glucose STEP 2 Fold into a hexagon.  Bond the C5 –O– to C1.  Place the C6 group above the ring.  Write the –OH groups on C2 and C4 below the ring.  Write the –OH group on C3 above the ring.  Write a new –OH on C1. 2/9/2016 Dr Seemal Jelani Introduction to Biochemistry 47 6 5 4 1 3 2

48. Cyclic Structure for Glucose (cont) 2/9/2016 Dr Seemal Jelani Introduction to Biochemistry 48  -D-Glucose  -D-Glucose   STEP 3 Write the new –OH on C1 down for the  form. up for the  form.

49. 2/9/2016 Dr Seemal Jelani Introduction to Biochemistry 49 Summary of the Formation of Cyclic Glucose

50.  Alcohols react with the carbonyl groups of aldehydes and ketones to give hemiacetal 2/9/2016 Dr Seemal Jelani Introduction to Biochemistry 50

51.  -D-Glucose and β-D-Glucose in Solution When placed in solution,  cyclic structures open and close.  -D-glucose converts to β-D-glucose and vice versa.  at any time, only a small amount of open chain forms.  -D-glucose D-glucose (open) β-D-glucose (36%) (trace) (64%) 2/9/2016 Dr Seemal Jelani Introduction to Biochemistry 51 O H CH 2 OH OH O C H OH OH OH OH OH OH CH 2 OH O OH OH OH OH CH 2 OH O

52.  Fructose and other ketoses with a long carbon chain also cyclizes to form hemiketal  D-fructose and D-ribose form a five- membered ring Intramolecular Cyclic hemiketal Structure of Fructose 2/9/2016 Dr Seemal Jelani Introduction to Biochemistry 52

53. Cyclic Structure of Fructose Fructose  is a ketohexose.  forms a cyclic structure.  reacts the —OH on C-5 with the C=O on C-2. 2/9/2016 Dr Seemal Jelani Introduction to Biochemistry 53 D-fructose  -D-fructose α-D-fructose

54.  This is two dimensional notation that specifies the 3- dimensional structure of cyclic form of carbohydrate Haworth Projection 2/9/2016 Dr Seemal Jelani Introduction to Biochemistry 54

55.  The D and L form of a monosaccharide is determined by the position of the terminal CH2OH gp on the highest-numbered ring carbon atom  In D-form, this group is positioned above the ring  In L-form the terminal CH2OH gp is positioned below the ring (not encountered in biological systems) 2/9/2016 Dr Seemal Jelani Introduction to Biochemistry 55

56.  α and β configurations is determined by the position of the –OH gp on carbon no 1 relative to the CH2OH  In β-configuration both of these gps point in the same direction  In α-configuration the two gps point in opposites direction 2/9/2016 Dr Seemal Jelani Introduction to Biochemistry 56

57.  Oxidation  Reduction  Glycoside formation  Phosphate ester formation  Amino sugar formation Reactions of Monosaccharides 2/9/2016 Dr Seemal Jelani Introduction to Biochemistry 57

58.  Yield three different types of oxidation products  Oxidizing agent used to determined the product Weak oxidizing Agent: Tollen's Reagent Benedict Solution Reducing Sugars Is a carbohydrate that gives a positive test with TR, FS and BS Oxidation 2/9/2016 Dr Seemal Jelani Introduction to Biochemistry 58

59.  Strong oxidizing agent oxidizes both end of monosaccharide i.e  Terminal pri-alcohol and carbonyl group to give dicarboxylic acid  Such polyhydroxy dicarboxylic acids are known as – aric acids  The oxidation of glucose gives Glucaric acid 2/9/2016 Dr Seemal Jelani Introduction to Biochemistry 59

60.  Carbonyl group present in a monosaccharide ( aldose, ketose) can be reduced to a Hydroxyl group using Hydrogen as a reducing group  Product is called Sugar Alcohol  D- Glucitol is also known as D-sorbitol  These are used as moisturizing agents in foods and cosmetics because of their affinity for water Reduction 2/9/2016 Dr Seemal Jelani Introduction to Biochemistry 60

61.  Cyclic forms of monosaccharides are hemiacetals and hemiketals react with alcohols to form Acetals and Ketals  The general name for monosaccharide acetals and Ketals is Glycoside  Glycoside  It is an Acetal or a Ketal formed from a cyclic monosaccharide Glycoside Formation 2/9/2016 Dr Seemal Jelani Introduction to Biochemistry 61

62.  Glycoside produced from glucose is Glycoside  Glycoside produced from galactose is Galactoside  Exist in α and β forms  Named as by listing alkyl or aryl group attached to the oxygen followed by the name of a monosaccharide involved with the suffix-ide 2/9/2016 Dr Seemal Jelani Introduction to Biochemistry 62

63.  The –OH gp of a monosaccharide can react with Oxoacids to form Esters  Phosphate esters are formed from phosphoric acid and various monosaccharides commonly encountered in biological system  Example  Specific enzymes in the body catalyze the esterification of the carbonyl group (C1) and the primary alcohol (C6) of glucose to give  Glucose-1-Phosphate  Glucose-6-Phosphate Phosphate Ester formation 2/9/2016 Dr Seemal Jelani Introduction to Biochemistry 63

64.  These phosphate esters of glucose are stable in aqueous solution and play important roles in the metabolism of carbohydrates 2/9/2016 Dr Seemal Jelani Introduction to Biochemistry 64

65.  Amino sugars of glucose, mannose and galactose are common in nature  They are produced by replacing the –OH group on carbon 2 on the monosaccharide with an amino group  Amino sugars and their N-acetyl-derivatives are important building blocks of polysaccharides such as cartilage  The N-acetyl derivatives of D-glucosamine and D-galactosamine are present in the biochemical markers on red blood cells, which distinguish the various blood type Amino Sugar formation 2/9/2016 Dr Seemal Jelani Introduction to Biochemistry 65

66. Disaccharides 2/9/2016 Dr Seemal Jelani Introduction to Biochemistry 66

67. A disaccharide consists of two monosaccharides. Monosaccharides Disaccharide glucose + glucose maltose + H 2 O glucose + galactoselactose + H 2 O glucose + fructosesucrose + H 2 O 2/9/2016 Dr Seemal Jelani Introduction to Biochemistry 67 Important Disaccharides

68.  Monosaccharide + Monosaccharide (Functioning as A hemiacetal or an alcohol) hemiketal) Disaccharide + H2O glycoside Disaccharides 2/9/2016 Dr Seemal Jelani Introduction to Biochemistry 68

69. Maltose is  A disaccharide also known as malt sugar.  Composed of two D-glucose molecules.  Obtained from the hydrolysis of starch.  Used in cereals, candies, and brewing.  Found in both the  - and β - forms.  The Glycosidic linkage between the two glucose units is called (1-4) linkage 2/9/2016 Dr Seemal Jelani Introduction to Biochemistry 69 Maltose

70.  Cyclic forms of monosaccharides are hemiacetals and hemiketals, they react with alcohols to form acetals and Ketals  The bond that links two monosaccharides of a disaccharide together is called a Glycosidic linkage  A Glycosidic linkage is the carbon-Oxygen-carbon bond that joins the two components of Glycoside together Glycosidic Formation 2/9/2016 Dr Seemal Jelani Introduction to Biochemistry 70

71. 2/9/2016 Dr Seemal Jelani Introduction to Biochemistry 71 Formation of Maltose Free α-OH

72.  Produced as an intermediate in the hydrolysis of the polysaccharide cellulose  Contains two D-glucose monosaccharide units  Differ from maltose –must have a β- configuration  β- (1-4)Glycosidic linkage  Reducing sugar having three isomeric forms in Aq. Solu and on hydrolysis produces two D-glucose molecules Cellobiose 2/9/2016 Dr Seemal Jelani Introduction to Biochemistry 72

73.  Different in biological behaviors  Differences are related to stereochemistry of their glycosidic linkages  Maltase enzyme which breaks glucose-glucose α (1-4) linkage present in maltose is found in human body and in yeast  That’s why maltose is easily digested by human body and readily fermented by yeast Difference in maltose and Cellobiose 2/9/2016 Dr Seemal Jelani Introduction to Biochemistry 73

74.  Both the human body and yeast lacks enzyme cellobiase which is needed to break the glucose- glucose β (1-4) glycosidic linkage of Cellobiose  Cellobiose cannot be digested by humans or fermented by yeast 2/9/2016 Dr Seemal Jelani Introduction to Biochemistry 74

75. Lactose  is a disaccharide of β-D- galactose and α- D- glucose.  contains a β -1,4- glycosidic bond.  is found in milk nearly 4- 9% and milk products. 2/9/2016 Dr Seemal Jelani Introduction to Biochemistry 75 α-form

76. 2/9/2016 Dr Seemal Jelani Introduction to Biochemistry 76 Sucrose Sucrose or table sugar is obtained from sugar cane and sugar beets. consists of α-D-glucose and β-D-fructose.. has an α,β-1,2-glycosidic bond. α-D-glucose β -D-fructose

77. Sugars and artificial sweeteners  differ in sweetness.  are compared to sucrose (table sugar), which is assigned a value of 100. 2/9/2016 Dr Seemal Jelani Introduction to Biochemistry 77 Sweetness of Sweeteners 60 000

78. Identify the monosaccharides in each of the following: A. lactose (1) α-D-glucose (2) β-D-fructose (3) β-D-galactose B. maltose (1) α-D-glucose (2) β-D-fructose (3) β-D-galactose C. sucrose (1) α-D-glucose (2) β-D-fructose(3) β-D-galactose 2/9/2016 Dr Seemal Jelani Introduction to Biochemistry 78 Learning Check

79. Polysaccharides 2/9/2016 Dr Seemal Jelani Introduction to Biochemistry 79 Copyright © 2005 by Pearson Education, Inc. Publishing as Benjamin Cummings

80. Polysaccharides  Are polymers of D-glucose.  Include Amylose and Amylopectin, starches made of α-D-glucose.  Include glycogen (animal starch in muscle), which is made of α-D-glucose.  Include cellulose (plants and wood), which is made of β-D-glucose. 2/9/2016 Dr Seemal Jelani Introduction to Biochemistry 80 α-D-Glucose

81. 2/9/2016 Dr Seemal Jelani Introduction to Biochemistry 81 Structures of Amylose and Amylopectin

82. Amylose Amylose is  a polymer of α-D- glucose molecules.  linked by  -1,4 glycosidic bonds.  a continuous (unbranched) chain. 2/9/2016 Dr Seemal Jelani Introduction to Biochemistry 82

83. Amylopectin  is a polymer of α-D- glucose molecules.  is a branched-chain polysaccharide.  has α-1,4-glycosidic bonds between the glucose units.  has α-1,6 bonds to branches. 2/9/2016 Dr Seemal Jelani Introduction to Biochemistry 83

84.  Starches like amylose and amylopectin hydrolyze to dextrins (smaller polysaccharides)  Contain 3-8 glucose units 2/9/2016 Dr Seemal Jelani Introduction to Biochemistry 84 Dextrins

85. Glycogen  is the polysaccharide that stores α-D-glucose in muscle.  is similar to amylopectin, but is more highly branched. 2/9/2016 Dr Seemal Jelani Introduction to Biochemistry 85

86. Cellulose  is a polysaccharide of glucose units in unbranched chains.  has β-1,4-glycosidic bonds.  cannot be digested by humans because humans cannot break down β-1,4-glycosidic bonds. 2/9/2016 Dr Seemal Jelani Introduction to Biochemistry 86