1 / 41

Carbohydrates Sugars or Saccharides

Carbohydrates Sugars or Saccharides. One of the most abundant compounds of living cells In living cells (plants) -> carbohydrates are made by photosynthesis Monosaccharides : C 3 -C 9 Oligosaccharides : 2-10 units. Monosaccharides (biological sugars –ose).

elina
Download Presentation

Carbohydrates Sugars or Saccharides

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. CarbohydratesSugars or Saccharides • One of the most abundant compounds of living cells • In living cells (plants) -> carbohydrates are made by photosynthesis • Monosaccharides : C3-C9 • Oligosaccharides : 2-10 units

  2. Monosaccharides (biological sugars –ose) Most frequently found in nature: - hexoses (six-carbon sugars) -> glucose and fructose - pentoses (five-carbon sugars) -> ribose Carbohydrates 2 Enantiomers S, R Configuration Fischer Projection Highest Oxidation state

  3. Monosaccharides (biological sugars –ose) Most frequently found in nature: - hexoses (six-carbon sugars) -> glucose and fructose - pentoses (five-carbon sugars) -> ribose Carbohydrates Pyranoside Furanoside Aldoses Ketoses

  4. Monosaccharides D-Aldoses in the range of C3-C6 Carbohydrates

  5. Monosaccharides D-Ketoses in the range of C3-C6 Carbohydrates

  6. Monosaccharides Stereochemistry Carbohydrates D-Erythrose + L-Erythrose -> Enantiomers D-Erythrose + D-Threose -> Diastereoisomers D-Erythrose + L-Threose -> Diastereoisomers D-glucose + L-glucose -> Enantiomers

  7. Monosaccharides Enolization and Isomerization Epimerization Epimerization Carbohydrates Base-catalysed in water: -> Epimerization + isomerization Isomerization

  8. Monosaccharides Cyclic hemiacetals + hemiketals Carbohydrates

  9. Monosaccharides Cyclic hemiacetals + hemiketals -> glucose Carbohydrates

  10. Monosaccharides Cyclic hemiacetals + hemiketals -> glucose Carbohydrates a b D L α-Sugars have the -CH2OH group and the anomeric hydroxyl group trans. β-Sugars have the -CH2OH group and the anomeric hydroxyl group cis.

  11. Monosaccharides Cyclic hemiacetals + hemiketals -> glucose Carbohydrates Glucopyranoside more stable -> almost 100% in pyranoside form

  12. Monosaccharides Cyclic hemiacetals + hemiketals -> ribose Carbohydrates In solution mainly in pyranoside form (76%) In nucleotides (or other combinations) mostly found in furanose form

  13. Monosaccharides Cyclic hemiacetals + hemiketals -> fructose Carbohydrates

  14. Monosaccharides Cyclic hemiacetals + hemiketals -> fructose Carbohydrates In solution mainly in pyranoside form (67%) In combinations mostly found in furanose form

  15. Monosaccharides The anomeric center Carbonyl group is planar -> attack of OH from either side possible -> 2 epimeric structures (anomers) Both anomers are in equillibrium in solution Carbohydrates Epimers: α -> anomeric center + highest chiral center -> different configuration (R,S convention) Hydroxyl (OH) on anomeric C Down -> α-D-sugars and β-L-sugars β -> anomeric center + highest chiral center -> same configuration (R,S convention) Up -> β-D-sugars and α-L-sugars Epimer (Anomer) Epimer (Anomer)

  16. Monosaccharides The anomeric center Carbonyl group is planar -> attack of OH from either side possible -> 2 epimeric structures (anomers) Both anomers are in equillibrium in solution Carbohydrates Epimers: β -> anomeric center + highest chiral center -> same configuration (R,S convention) α -> anomeric center + highest chiral center -> different configuration R,R-> β S,R-> α

  17. Monosaccharides The anomeric center Carbonyl group is planar -> attack of OH from either side possible -> 2 epimeric structures (anomers) In solution -> all 4 forms in equillibrium !!! Carbohydrates Aldohexoses Ketose

  18. Monosaccharides The anomeric center Esterfication -> freezes sugar in its anomeric form (no interconvertion between α and β any more) Carbohydrates

  19. Monosaccharides Alditols Reduction of sugars -> reducing agent (NaBH4) -> reduces aldehydes + ketons Reduction occurs at small amount of open chain form -> shift in equilibrium -> total reduction achieved Reduction of Aldoses -> 1 product (primary alcohol) -> Alditols Reduction of Ketoses -> 2 products (secondary alcohol) -> Alditols Carbohydrates

  20. Monosaccharides Glycosides (replace suffix –ose with –oside) -> Reaction at C1 (anomeric C) Hemiacetals + Alcohol -> Acetals (Glycoside) Hemiketals + Alcohols -> Ketals (Glycoside) Carbohydrates OH on the anomeric C1

  21. Monosaccharides Glycosides (replace suffix –ose with –oside) Hemiacetals + Alcohol -> Acetals (Glycoside) Hemiketals + Alcohols -> Ketals (Glycoside) Carbohydrates

  22. Monosaccharides Glycosides (replace suffix –ose with –oside) -> Reaction at C1 Hemiacetal/Hemiketal + Alcohol -> O- Glycoside -> Polysaccharides Hemiketal/Hemiketal + Amine -> N-Glycoside Carbohydrates

  23. Monosaccharides Glycosides (replace suffix –ose with –oside) Hemiacetal/Hemiketal + Alcohol -> O- Glycoside -> Polysaccharides Hemiketal/Hemiketal + Amine -> N-Glycoside Carbohydrates Template for aspirin Nucleotides of RNA and DNA

  24. Monosaccharides Glycosides (replace suffix –ose with –oside) Glucose + MeOH -> Acetal -- reaction works directly Glucose + complex alcohol -> not that easy Carbohydrates Example: Production of salicin -> Template for Aspirin

  25. Monosaccharides Glycosides (replace suffix –ose with –oside) Glucose + MeOH -> Acetal -- reaction works directly Glucose + complex alcohol -> not that easy Carbohydrates Example: Production of salicin -> Template for Aspirin

  26. Monosaccharides Cyclic Acetals + Ketals -> protecting groups 2 OH groups are cis conformation -> reaction with keton Carbohydrates C6

  27. Monosaccharides Modified sugars -> in cell membranes Carbohydrates

  28. Oligosaccharides -> a few monomers Carbohydrates Found in dietary products

  29. Polysaccharides Carbohydrates In Plant cell wall -> cotton In animal and plant cells

  30. Polysaccharides Glycogen -> mammalian sugar storage Carbohydrates

  31. Polysaccharides Starch: amylose + amylopectine -> main plant food reserve Carbohydrates

  32. Polysaccharides - Hydrolysis • Chemically: - under harsh conditions: with hot acid -> monosaccharides (glucose) • - under mild conditions: with acid -> oligosaccharides (randomly) • 2. Enzymatic: very specific hydrolysis • -> α-amylase -> hydrolysis α 1 -> 4 bonds in starch (mainly maltose + glucose) • -> α-1,6-glucosidase -> hydrolysis α 1 -> 6 bonds in starch • -> lactase -> hydrolysis lactose • (high activity of enzyme in infants – low activity in adults -> intolerance) • -> cellulase -> hydrolysis β 1 -> 4 bonds -> animals do not have it (need bacteria) Carbohydrates

  33. Oxidation of sugars Under mild conditions -> with cupric ion (Fehling’s solution) or Br2 -> oxidation of aldehyde group -> acid (aldonic acid) If sugars are glycosidic linked (acetal formation) -> aldehyde group not available for oxidation -> no reducing sugars If sugar are free -> reducing sugars Carbohydrates

  34. Oxidation of sugars Under strong conditions -> with HNO3 -> oxidation of aldehyde group + alcohol groups (primary alcohol) -> diacid (aldaric acid) Carbohydrates

  35. Oxidation of sugars Determination of glucose level in blood or urine -> oxidation of glucose –> H2O2 involved in second reaction -> colorimetric or voltametric sensor (Biosensor) Diabetes mellitus: Insulin deficiency Insulin regulates blood sugar (glucose) level If glucose level is high -> insulin level increases -> prevents break down of glycogen into glucose and conversion of fat or protein into glucose -> blood glucose level will sink again If glucose level is low -> insulin level drops -> more glucose produced -> blood glucose level will rise Carbohydrates

  36. Oxidation of sugars Also oxidized by most enzymes Terminal OH group oxidized in Aldoses -> Uronic acids Carbohydrates Pectins: in cell walls of fruits -> acid solutions form gels -> jam making

  37. Oxidation of sugars Terminal OH group oxidized in Aldoses -> Uronic acids Carbohydrates Pain reliefer Even stronger pain reliefer Morphine metabolism in human body -> make it more soluble -> excretion

  38. Oxidation of sugars Vitamin C: most animals can synthesize Vitamin C – Humans and primates cannot NOT -> synthesized in liver from glucose Essential for: - formation of structural proteins in skin, bones, ligaments - cofactor in synthesis reactions of amino acids and modifications - antioxidants Carbohydrates Deficiently (scurvy) -> muscular pain, skin lesions, fragile blood vessel, bleeding gums, tooth loss

  39. Aminosugars Replacement of one OH group by a amino group In nature -> done by enzymes -> 2-amino-2-deoxy sugars Carbohydrates Chitin: insect skeleton and shells of crustaceans

  40. Aminosugars Replacement of one OH group by a amino group In nature -> done by enzymes -> 2-amino-2-deoxy sugars Bacterial cell walls -> glycycosidic bond cleaved by lysozyme Carbohydrates Lysozyme β-lactam antibiotics -> inhibit peptidase linking peptide bond during biosythesis of cell wall

  41. Aminosugars Replacement of one OH group by a amino group In nature -> done by enzymes -> 2-amino-2-deoxy sugars Carbohydrates Blood groups: Determined by glycoproteins

More Related