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CARBOHYDRATES (SACCHARIDES, SUGARS)

CARBOHYDRATES (SACCHARIDES, SUGARS). (MONOSACCHARIDES, SIMPLE SUGARS). PHOTOSYNTHESIS. Saccharide classification. Monosaccharides (simple sugars) Glucose Mannose Ribose. Oligosaccharides Sucrose Lactose Maltose. Polysaccharides Starch Cellulose Pectins.

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CARBOHYDRATES (SACCHARIDES, SUGARS)

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  1. CARBOHYDRATES (SACCHARIDES, SUGARS)

  2. (MONOSACCHARIDES, SIMPLE SUGARS)

  3. PHOTOSYNTHESIS

  4. Saccharide classification Monosaccharides (simple sugars) Glucose Mannose Ribose Oligosaccharides Sucrose Lactose Maltose Polysaccharides Starch Cellulose Pectins Hydrolyze to simple sugars. Contain many monosugars linked together Not hydrolyze to smaller molecules Hydrolyze to simple sugars. Contain 2-10 monosugars linked together

  5. Monosaccharide structures an aldohexose a ketohexose an aldopentose

  6. Naturally occurring D-sugars (R)-(+)-glyceraldehyde Configuration at stereogenic center farthest from the carbonyl group is on the right in Fischer projection

  7. D-Aldoses an aldotriose aldotetroses

  8. D-Aldoses aldotetroses aldopentoses

  9. D-Aldoses

  10. D-Aldoses Allose Altrose Glucose Mannose Gulose Idose Galactose Talose All Altruists Gladly Make Gum In Gallon Tanks

  11. D-Ketoses a ketotriose a ketotetrose a ketopentose a ketopentose

  12. D-Ketoses ketopentoses ketohexoses

  13. Cyclic forms of monosugars In monosugars carbonyl and hydroxyl groups are in the same molecule, so hemiacetal formed is a 6- or 5-membered ring with one oxygen atom – pyran or furan analogue

  14. Cyclic forms of monosugars D-glucose, pyranose form D-fructose, furanose form

  15. 6- and 5-membered oxygen heterocycles

  16. Interconversion of Fischer and Haworth projections D-glucose (Fischer) D-glucose (Haworth))

  17. Two stereoisomers of pyranose form (anomers) α-D-glucopyranose 36% β-D-glucopyranose 64% α anomer β anomer

  18. Mutarotation of monosaccharides α-D-glucopyranose (36%) [α]D = +112.2° β-D-glucopyranose (64%) [α]D = +18.7° At equilibrium [α]D = +52.6°

  19. Chair conformations of glucopyranose anomers α-D-glucopyranose β-D-glucopyranose

  20. Chair conformations of glucopyranose anomers Anomeric carbon (C1) Anomeric carbon (C1) α-D-glucopyranose β-D-glucopyranose

  21. β-D-glucopyranose Anomeric hydroxyl

  22. Physical properties of hexoses • Crystalline solids, non-volatile, decompose at elevated temperature (caramelization) • Polar, very well soluble in water, soluble to some extent in lower alcohols, insoluble in nonpolar organic solvents • Form oversaturated solutions in water (syrups) – difficult for crystallization

  23. Chemical properties of hexoses • Enolization (isomerization) • Oxidation • Reduction • Glycoside formation (acetals) • Acylation (esters formation) • Alkylation (ethers formation) • Reactions with nitrogen nucleophiles • Kiliani-Fischer chain lengthening • Wohl degradation (chain shortening)

  24. Chemical properties of hexoses • Enolization (isomerization) D-glucose, D-mannose Keto-enol tautomerism (base or acid-catalyzed)

  25. Chemical properties of hexoses • Oxidation Tollens reagent Fehling reagent Ag0 Red solid Silver mirror

  26. Chemical properties of hexoses • Oxidation Oxidation of aldehyde group of aldose leads to aldonic acid

  27. Chemical properties of hexoses • Oxidation Oxidation of aldehyde and hydroxymethyl groups of aldoses leads to dicarboxylic aldaric acids

  28. Chemical properties of hexoses • Oxidation Oxidation of hydroxymethyl group of aldose leads to uronic acid

  29. Chemical properties of hexoses • Reduction Reduction of aldehyde group of aldoses leads to alditols

  30. Acetal formation from hemiacetal Cyclic monosugar + alcohol → Glycoside + water

  31. Chemical properties of hexoses • Glycoside formation Acetal Hemiacetal

  32. Glycosides in nature Bearberry Methylarbutin Skin-lightening activity

  33. Glycosides in nature Willow Salix alba Salicin Anti-inflammatory activity

  34. Glycosides in nature Aglycon Amygdalin Cyanogenic glycoside

  35. Properties of glycosides • Exist as two distinct anomers - α or β • Do not show reducing properties (ring does not open) • Mutarotation is not possible (ring does not open) • Stable in alkaline aq. solutions (like ethers) • Hydrolyze in acidic aq. solutions into sugar and aglycon

  36. Chemical properties of hexoses • Acylation (esters formation)

  37. Chemical properties of hexoses • Alkylation (ethers formation)

  38. Chemical properties of hexoses • Reactions with nitrogen nucleophiles Reaction with hydroxylamine leads to D-glucose oxime

  39. Chemical properties of hexoses • Reactions with nitrogen nucleophiles Reaction with phenylhydrazine leads to D-glucose phenylhydrazone

  40. Chemical properties of hexoses • Reactions with nitrogen nucleophiles Reaction with excess of phenylhydrazine leads to D-glucose osazone

  41. Chemical properties of hexoses • Reactions with nitrogen nucleophiles D-glucose osazone can be converted into osone – 1,2-dicarbonyl derivative

  42. Kiliani-Fischer chain lengthening of monosugars

  43. Kiliani-Fischer chain lengthening of monosugars

  44. Wohl degradation (chain shortening) of monosugars

  45. GLYCOSIDES Monosugar + alcohol Glycoside + water Aglycon: 4-methoxyphenol Sugar: D-glucose

  46. OLIGOSACCHARIDES

  47. OLIGOSACCHARIDES Monosugar + monosugar Disaccharide + water 1β,4’ glycoside bond Cellobiose, a 1,4’-β-glycoside D-Glup-(β1→4)-D-Glup

  48. CELLOBIOSE 1’ 1 4’

  49. MALTOSE 1α,4’ glycoside bond Maltose, a 1,4’-α-glycoside D-Glup-(α1→4)-D-Glup

  50. MALTOSE Maltose and cellobiose are diastereoisomers. The only differrence is the configuration of glycoside bond – α in maltose, β in cellobiose.

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