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Carbohydrates

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  • 1. Carbohydrates biochemistry
  • 2. Monosacchrides (A) Classification (B) Structure cyclization (C) Joining Aldoses ketose Isorners Epimers Enantiomers DI- Oligo- Poly- Containing Aldehyde gp keto gp H – C - = O I I C = O I D – Sugar L – sugar linear Branch The bonds that link sugars. e.g., (starch) (glycogen) Glycosiclic bond,
  • 3. CARBOHYDRATE → Polyhydroxylated compounds ē at least 3 – carbon atoms ē potentially active carbonyl group which may either be aldehyde, or ‘ketone’ groups. → Also called sacchrides / sugar → Empirical formula (CH20)n
  • 4. Classification of carbohydrates 1 – Monosaccharides. 2 – Disaccharides. 3 – polysacchrides. 4– Derived Carbohydrates Oxidation and reduction products Amino and Deoxy sugars. Homopolysacchrides Heteropolysacchrides Mucopolysacchrides Mucilages Hemicellulose
  • 5. (1). Monosacchrides “ simple sugars ḛ Cannot be further hydrolysed” → they are either aldoses containing aldehye group or ketoses containing ketone group. → white crystalline solids → very soluble in water. → most have sweet taste H R I I C=O C=O I I R R Aldehyde ketone group group
  • 6. Generic Names Aldoses Ketoses Trioses (C3H6 03) glycerose/ Glyceraldehydes dihydroxyacetone Tetroses (C4 H8O4) Enythrose Erthrulose Pentoses (C5H10 O5) Ribose Ribulose Hexoses (C6H10 O6) Glucose Fructose Heptoses (C7H14 O7) Glucoheptose sedoheptulose
  • 7. (2). Oligosaccrides “Condensation products of 3 – 10 monosacchrides” Most are not digested by human enzymes. Monosacchrides attach each other by glycosidic linkages.
  • 8. For example,  - Dextrin ( polymer of 8 – glucose molecules) Maltolriose ( polymer of 3 glucose molecules ) Isomaltose and trehalose.
  • 9. (3). disacchrides “Condensation products of 2 monosacchrides For Example Maltose (glucose + glucose). Sucrose (glucose + fructose). Lactose (glucose + galacose) → hydrolysis of sucrose produces a mixture of glucose and fructose called “Invert sugar” b/c fructose is strongly levorotatory and changes the weaker dextrorotatory action of sucrose.
  • 10. (4). Polysaccharides “condensation products of >10 monosacclrides” → they serves as stores of fuel. → forms structural elements of cells. (a). Homopolysacclrrides. They contains only one type of monosacchrides e.g., starch, glycogen, cellulose and dextrins.
  • 11. (b). Heteropolysacchrides. They contain a no of diff. monosacchrides e.g., Mucopolysacchrides Hyaluronic acid, heparin, chondroitin sulphate, blood group polysacchrides, serum mucoid . Mucilages Agar, vegetasle gums and pectin. Hemicellulose .
  • 12. (5). Derived carbohydrates Derived from carbohydrates by various chemical reactions. (a). Oxidation products derived from glucose on its oxidation e.g., gluconic acid, glucuronic acid, glucaric acid and ascorbic acid (vits). (b). Reduction products glycerol and ribitol derived from glyceraldehydes and ribose.
  • 13. ( c). Amino sugar These have NH2 group at carbon No 2 include glucosamine, galactosamine, manosamino derived from glucose galactose and manose respectively. (d). Deoxy- sugar They have less no of oxygen atoms than parent sugar e.g., 2 – deoxyribose present in DNA has one oxygen atom less as compared to ribose.
  • 14. Structure of monosacchrides (1). Isomers “ compounds that have same chemical formulas” e.g., glucose, galactose, fructose and mannose all have same chemical formula C6H12O6 (hexoses). (2). Epimers “Two isomers ḛ differ in configration around one specific Carbon atom other than the carbon atom of carbonyl group called epimers. Glucose and galactose → carbon 4 epimers Glucose and mannose → carbon 2 epimers.
  • 15. ¹CHO ¹CHO I I H – C2 – OH H – C2 - OH I I H – C3 – OH H – C3 – OH I I OH – C4 – OH H – C4 – OH I I H – C5 – OH H – C5 – OH I I H – C6 – OH H – C6 – OH I I H H ¹CHO ¹CH2OH I I OH – C2 – H C2 =O I I H – C3 – OH OH – C3 – H I I H – C4 – OH H – C4 – OH I I H – C5 – OH H – C5 – OH I I H – C6 – OH H – C6 – OH I I H H Aldoses Keto sugar Galactose Glucose Mannose Fructose C4- epimers C2 – epimers all Isomers of each other
  • 16. Enantiomers or optical isomers or stereoisomers NAMING ENANTIOMERS (a) By configration D – sugar L – sugar (b) By Optical Activity Levorotatory ‘l’/- ve (3) Dextrorotatory ‘d’/+ ve
  • 17. Levorotatory and dextrotatory substances Substance moving the plain polarized light to the left and right are called levo. and dextrorotatory respectively as ‘l’(-ve) and ‘d’ (+ve) → optical activity of sugar is dlt presence of asymmetrical c. atoms
  • 18. As Dihydroxyacetone has no asymmtric carbon so it has no optical activity. ¹CH2OH I ²CH = O I ³CH20H → Enantiomers have some physical and chemical properties bt rotate PPL in opposite directions.
  • 19. POLARIMETER The instrument ē which optically active compounds are studiedis a polarimeter Emergent Light ē rotated Plane of the polarizationNicol Prism Polarizer The rotation in degree of / gm of substance /ml of the Solvent in a tube of one dm (10 Cm )in length in called Specific rotation Unpolorized Light osscilating in all planes (source) Incident Plane – polarized Light osscilating In one plane Polarimeter Tube containing Sol of an optical Isomer Nicol prism analyzer Levorotatory Dextrorotatory Anticlockwise clockwiseT = temp of rotation D = Na light ʎ (589 nm) Obs = observed rotation in a tuse C = conc of substance g/ml L = length of tuse in dm [ ] = rotation [ ] = obs D l x C T
  • 20. (3). Enantiomers “ a pair of structures that are mirror images of each other in regard to asymmetric carbon atoms present in their molecules” e.g., Glucose occurs as D and L glucose isomers. The name D and L depends upon the position of OH group on the last asymmetric cabon atom ( to which 4 diff atoms or groups are attached) of monosacchride.
  • 21. C¹HO C¹HO I I H – C2 – OH HO – C2 – H I I OH – C3 – H H – C3 – OH I I H – C4 – OH HO – C4 – H I I H – C5 – OH HO – C5 – H I I CH20H CH20H D – glucose L – glucose 6 6 mirror
  • 22. → The structure of the smallest sugar containing 3 – C atoms namely Glyceraldehydes also called “ Referance sugar” C¹HO C¹HO I I H – C2 – OH OH – C2 – H I I H – C3 – OH H – C3 – OH I I H H D – glyceraldehyde L – glyceraldehyde
  • 23. (a). D – sugars all such sugars whose asymmetric C – atom situated farthest from the potential aldehyde or ketone gp has the same configration as the asymmetric C-atom of D- glyceraldehyde are called D – sugar.
  • 24. (b). L – Sugars All sugars whose carbon atom situated farther from the potential aldehyde or ketone gp has the same configration as the asymmetrical c. atom of L – glyceraldehydes are called L – sugars.
  • 25. CYCLIZATION (Hemiacetal/ Hemiketal rings) pyranose furanose Anomeric 1 Mutarotation 2 Representation 3 Anomers 4 Carbon v Fischer projection formula. Haworths ‘’ ‘’ ‘’ Boat and chair forms  - sugar. Β – sugar . Anomeric Isomers or diast- Ercomers. OH gp not altach Covallently attach To other molceule to other molecule Ring open and aldehyde if attach to if attach gp of acyclic sugar - OH gp to – NH2 gp Oxidized Reducing sugar O – Glycoside N – glycosidic linkage likage v 5 Glycosidic Bone V
  • 26. Cyclization of monosacchrides Each Monosacchride exists in Open chain (acyclic) form and predominantly in ring form. Hemiacetal or Hemeketal ring Aldehyde or Keto group has reacted ē an alcohol group on the same sugar to from hemiacetal or hemiketal ring. (4).
  • 27. (a). Pyranose ring if resulting ring has 6 members (5C and 1 oxygen). (b). Furanose, ring if it is 5 membered (4C and 1 oxygen) (1). ANOMERS aldehyde/ keto gp cyclize to produce ammonic C atom. These are isomers that differ in configration around the anomcric carbon atom i.e., the carbon atom of the carbonyl group carbon No 1 in aldoses and carbon No 2 in ketoses.
  • 28. OH H H OH C C I I H – C – OH H – C – OH I I β – D OH – C – H H0 – C – H I I H – C - OH H – C – OH I I H – C - H – C I I H – C – OH H – C – OH I I H H β – D glucopyranose - D Glucopyranose The 2 types anomers called and - β anomers.
  • 29. (2). Mutarotaion Thy cyclic and β anomers of sugar in a solution can readily be interconverted and are in equillibrium with each others e.g., a sotuain of pure D – glucose in water. Produces an equilibrium mixture of about 64% β – D glucose and 36 % - D glucose.
  • 30. OH H O H OH II ¹C C – H ¹C I I I H - ²C – OH H – C – OH H - ²C- OH I I I HO - ³C – H HO – C – H HO - ³C – H I I I H – C – OH H – C – OH H – C – OH I I I H – C - H – C – OH H – C I I I H – C – OH H – C – OH H – C – OH I I I H H H β – D glucopyranose +19º (64%) D – glucose - D glucopyranose (36%) +112º
  • 31. It is dlt the fact that being dissolved in water the glucose molecules going on changing from one to another from each having a diff. optical rotation of polarized light. An equilibrium is reached after the passage of sometime and the specific rotatin becomes fixed.
  • 32. (3). representation of sugar conformation. H OH C1 I H – C – OH I HO – C – H I H – C – OH I H – C – I H – C – OH I H (a). Fischer Projection formula carbon chain is written vertically ē C1 at the top. - D glucose
  • 33. Carbon 1 is drawn farthest to the right and - H , - OH and CH20H projects either above and below the plane of paper. (b). Haworth projection formula
  • 34. 5 H 5 H H 5 OH H H 4 1 4 1 4 1 OH H OH H 3 2 3 2 3 2 OH H 1 → 5 ring H OH H OH pyran CH20H CH20H 6 6 β – D glucopyranose- D glucopyranose
  • 35. O O O CH20H CH20H I I H – C – OH H – C – OH H OH 4 1 3 2 3 2 OH H OH H H OH H H 4 1 3 2 1 – 4 ring H OH H OH Furan - D glucofuranose β – D glucofuranose 6 6 5 5
  • 36. ( C). Boat and Chair forms. Provides more exact representation of the three diamentional conformation of sugar in nature.
  • 37. Glycosidic Bonds Glycosidic bonds B/w sugar are named according to no of connected carbons and ē regard to the position of anomeric. – OH gp of sugar involved in the bond. oThe linkage is an bond if anomeric OH is in configration. oThe linkage is a β – bond if anomeric OH is in β – configration. (4).
  • 38. β – Galactose β – Glucose → Lactose β(1 – 4 glycosidic bond) is reducing sugar b/c anomaric end of glucose is not involved in glycosidic linkage. CH2OH CH2OH O O OH H OH O 5 5 4 1 4 1 OH OH 3 2 3 2 H OH OH 6 6 H
  • 39. CHEMICAL PROPERTES OF MONOSACCHRIDES (1). Reacting ē hydrazine's to form osazones. Meating of sugars containing aldehyde or ketone group ē phenylhydrazine produces phenylosazones e.g., Glucose + 3(C6H5NHH2) → glucosazone + C6H5NH+NH3 + 2H20 fructose, glucose and mannose form identical osazones called glucosazone.
  • 40. Galactose → Galactosazone. Maltose → Maltosazone. Lactose → lactosazone. Lactose and maltose forms osazones crystals. Sucrose not form osazones. (2). Reduction to form sugar Alcohol. Both aldoses or ketoses may be reduced at their addehyde and ketone groups to produce corresponding polyhydroxy alcohol.
  • 41. Glucose → sorbitol Manose → Manitol Fructose → sorbitol + manitol glyceraldehyde → Glycerol Ribose → Ribitol MANITOL is used in pt ē cerebral edema b/c it acts as osmotic diuretic and ↓es water content of body thus ↓es Brain swelling.
  • 42. SORBITOL Get deposited in the lense of eyes of diabetic pt and contribute to Cataract formation.
  • 43. (3). Oxidation to produce sugar acids. On oxidation give 3 types of sugar acids. Gluconic acid → at C1. Glucuronic acid – at C6. Gluconic acid – both at C1 and C6.
  • 44. GLUCURONIC ACID. → It is used in the process of detoxifying and inactivating many substances in body like benzoic acid, steroid hormones and bilirubin. → In all plants and mammals it is used as a precursor of Ascorbic acid (vitc)
  • 45. (4). Reduction Action of sugar in Alkaline solution. Any of the sugar containing potentially free aldehyde or ketone groups possesses the property of readily reducing alkaline solutions of many mettalic salt such as Cu Ag, Bi , Hg , Fe. +2 + +3 + +3
  • 46. Examples of reducing sugar. Glucose, galactose, glyceraldehydes lactose and maltose. Non reducing sugar. Sucrose and trehalose, glycosides. → Test used for detection of presence of red. Sugar. Benedicts reagent. Fehling’s solution.
  • 47. (5). Action of Acids. Monosaccharide's are resistant to actions of hot dilute mineral acids. Strong acid remove water from sugar to form organic compocuds furfurals C5H10 05 → C5 H4 O2 + 3H2o (6). Action of Bases Dilute basic solutions at low temp can bring about a rearrangement of groups around anomeric C. atom and its adjacent C. atom e.g., glucose can be changed to fructose and mannose.
  • 48. (7). Formation of Esters The OH group of sugars may be esterified to form Estes. Such as phosphates, acetates, proprionates, Sugar phosphate back bone form the structural framework of nucleic acid (DNA and RNA).
  • 49. (8). Formation of amino sugars The OH group of monosacdride can be replaced by an amino (- NH2) group forming an amino sugar e.g., D – glucosamine → hyaluronic acid. D – galactosamine → Chondroitin. D – manosaming → mucoprotein. Amino sugars also present in antibiotics e.g., in Erythromycin.
  • 50. (9). Fermentation. Breakdown of sugars by bacteria and yeasts using a method of respiration. ē out oxygen (anrerobic). C6H12O6 → 2 C2H5OH + 2CO2 (glucose) (ethanol). Uses production of Yogurt. Alcoholic Beverages. Pickles Bread. Fuel.
  • 51. (10). Formation of Glycosides. Glycosides are compounds in ḛ a carbohydrate residue (e.g., glucose) is attached by an acetal linkage at anomeric C . atom to an alcohol residue called a glycon ḛ is non- carbohydrate. → Aglycon attach to sugar thr. OH gp or – NH groups. forming O – and N – glycoside respectively.
  • 52. For example Sugar + asparagine → N – glycosidic bond. Sugar + serine → O – glycosidic bond.
  • 53. H OH H C C I I H – C – OH H – C – OH I I HO – C – H HO – C – H I I H – C – OH H – C – OH I I H – C H – C – I I CH2OH CH2OH - D glucose β – D glucose CH3OH Methyl Alcohol
  • 54. H OCH3 HCO H C C I I H – C – OH H – C – OH I I HO – C – H HO – C – H + H2O I I H – C – OH H – C – OH I I H – C H – C I I CH2OH CH2OH 3 Methyl - D methyl β – D Glucose Glucose Acetal inkage is used for both Ketones aldehyde
  • 55. Cardiac Glycosides (Digoxin) Drugs used in of CCF and Cardiac arrythmias (AF) Glycoside hydrolases (Glycosidases) Catahyse the hydrolysis of glycosidic linkage to release small sugars. o cellulases used for degrading cellulose to glucose.
  • 56. Invertase for manufacturing of invert sugar (Honey food industry). Xylanases for removing hemicellulose from paper pulp (paper and pulp industry).