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Carbohydrates

Carbohydrates. Energy Cycle of Life. Formula: (CH 2 O) n (with n ≥ 3) Trioses: n=3 Tetroses: n=4 Pentoses: n=5 Hexoses: n=6 Heptoses: n=7 Octoses: n=8 Sugars contain one aldehyde or ketone carbonyl and at least two alcohols.

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Carbohydrates

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  1. Carbohydrates

  2. Energy Cycle of Life

  3. Formula: (CH2O)n (with n ≥ 3) Trioses: n=3 Tetroses: n=4 Pentoses: n=5 Hexoses: n=6 Heptoses: n=7 Octoses: n=8 Sugars contain one aldehyde or ketone carbonyl and at least two alcohols. Pentoses and hexoses can be linear or cyclic (cyclic or ring form favored under physiological conditions) Monosaccharides (Monomeric Sugars)

  4. Trioses: The Simplest Monosaccharides Aldehyde-containing sugar = aldose Ketone-containing sugar = ketose

  5. Aldose-Ketose Interconversion via Enediol Intermediate Note: Isomerization of dihydroxyacetone phosphate to glyceraldehyde-3-phosphate during glycolysis is catalyzed by triose phosphate isomerase, a “perfect enzyme.”

  6. The Enantiomers of Glyceraldehdye Most naturally occurring sugars are D-sugars.

  7. RS Nomenclature System (Cahn, Prelog, Ingold System)

  8. Some Abundant Monosaccharides

  9. Stereochemistry of Aldotetroses <- Enantiomers -> <- Enantiomers -> <- Diastereomers ->

  10. The Two Enantiomers of the Ketotetrose Erythrulose

  11. Stereochemical Relationships of the D-Aldoses

  12. Stereochemical Relationships of the D-Ketoses

  13. Cyclization of Hexoses Pentoses can cyclize also (e.g., ribofuranose).

  14. Pyranoses vs. Furanoses

  15. Pyranose Ring Sugars in Chair and Boat Conformations Chair conformation more stable

  16. Conformations of Chair Form of a Pyranose

  17. The Two Chair Conformations of b-D-Glucopyranose Conformation on the left more stable since relatively bulky OH and CH2OH groups all occupy equatorial positions (in the conformation on the right they occupy more crowded axial positions).

  18. Conformational Isomers of Furanoses

  19. a and b Anomers of Glucose a anomer b anomer Anomers: different configurations at C1

  20. The Four Most Common Hexoses

  21. Abundance of Different Forms of Some Monosaccharides

  22. Terminology Describing Structure of Sugars

  23. Derivatives of the Monosaccharides

  24. Modified Sugars

  25. Acid and Lactone Derivatives Oxidation of a monosaccharide yields the corresponding acid and lactone derivatives.

  26. Alditols Reduction of the carbonyl group on a sugar yields the corresponding alditol.

  27. Amino Sugars Often found in complex oligo- and polysaccharides.

  28. Glycosides and the Glycosidic Bond

  29. Two Toxic Glycosides Produced by Plants Inhibits Na+/K+ ATP-dependent pump Yields hydrogen cyanide (HCN) on hydrolysis.

  30. Oligosaccharides

  31. Structures of Some Important Disaccharides Reducing sugar ide Non-reducing sugars H A reducing sugar has a free anomeric carbon not in glycosidic bond (free hemiacetal or hemiketal).

  32. Reducing sugars

  33. Occurrence of Some Dissaccharides

  34. Formation of the Glycosidic Bond

  35. Formation of Lactose in vivo

  36. Storage polysaccharides Structural polysaccharides Glycosaminoglycans Polysaccharides

  37. Amylose: A Linear Glucose Polymer (Glucan) A major storage form of glucose in plants. Polymer of a-D-glucopyranosewith a(1->4) glycosidic linkages

  38. Amylopectin: A Branched Glucan Another storage form of glucose in plants. a(1->4) and a(1->6) glycosidic linkages R = reducing end N = nonreducing end

  39. Also a branched glucan with a(1->4) and a(1->6) glycosidic linkages linkages, like amylopectin. Has more frequent a(1->6) branches. Glycogen: The Major Storage Form of Glucose in Animals Glycogen granules in a liver cell

  40. Organization of Plant Cell Walls

  41. Cellulose: A Structural Polysaccharide in Plants Polymer of b-D-glucopyranosewith b(1->4) glycosidic linkages

  42. Chitin: A Structural Polysaccharide in Exoskeletons of Many Arthropods and Mollusks Polymer of N-acetyl-b-D-glucosamine (GlcNAc) with b(1->4) glycosidic linkages

  43. Repeating Structures of Some Glycosaminoglycans Glycosaminoglycans constitute the carbohydrate component of proteoglycans, conjugates of glycosaminoglycans and proteins, with structural functions in vertebrate cartilage and connective tissue.

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