12_Carbohydrate

12_Carbohydrate - Chem 267 Basic Organic Chemistry II Prof....

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Prof. Dr. Xiangdong Fang University of Waterloo Chem 267 Basic Organic Chemistry II 1
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2 Carbohydrates: Name Origin, Nature Presence 1) the name of “carbohydrates” originates from their empirical formulas, C m (H 2 O) n , that look like hydrated carbon; 2) carbohydrates are the most abundant class of organic molecules found in living organisms, as both plants and animals synthesize and metabolize carbohydrates; 3) nature synthesizes carbohydrates through photosynthesis, which converts CO 2 and H 2 O into glucose and releasing O 2 at the same time; while glucose can be oxidized to CO 2 and H 2 O and provides energy for living cells. Solar Energy Energy for Cells CO 2 + H 2 O + O 2 carbohydrates
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3 triphosphate ribose adenine chemical energy from carbohydrate oxidation ATP synthase ADP ATP Energy Transfer Involving ATP (Adenosine Triphosphate)
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4 Carbohydrates also act as a biosensor interacting between cells and their environments “carbohydrates play fundamentally important roles in every aspect of bio-recognization processes and signal transductions”
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5 Carbohydrates 1) carbohydrates (also called “ saccharides ”) are polyhydroxy aldehydes ( aldose ) and ketones ( ketose ) or their derivatives; 2) the properties of carbohydrates are quite different depending on their unique molecular structures.
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6 D and L System in Carbohydrates 1) D/L designation is completely arbitrary; 2) D/L system is based on the followings: (a) (+)-glyceraldehyde is arbitrarily assigned with the OH group at C2 to the right side in its Fischer projection; (b) a monosaccharide belongs to the D-family if the OH group on the chiral carbon farthest to C1 is also on the right side in its Fischer projection; otherwise it would be assigned as L system.
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7 Configurational Isomers in Glucose CHOH CHO CHOH CHOH CHOH CH 2 OH 1 2 3 4 5 6 glucose 4 chiral centers 2 4 = 16 possible configurational isomers CHOH CHO CHOH CHOH C CH 2 OH 1 2 3 4 5 6 glucose 4ch ira lcenters, but one is fixed H OH 2 3 = 8 possible configurational isomers with the fixed configuration at C5 (D-configuration) you only have to know three of them: D-glucose , D-mannose
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8 Fischer Projection for D-Aldose Family (Three to Six-Carbon Atoms)
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9 Fisher Projection for D-Ketose Family (Three to Six-Carbon Atoms)
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10 Aldose and ketose are structural isomers CHO OH H HO H H OH H OH CH 2 OH D-glucose aldose (containing aldehyde) C CH 2 OH O HO H H OH H OH CH 2 OH D-fructose ketose (containing ketone)
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11 1) D-galactose, and D-mannose are diastereomers (non-superimposable mirror images); 2) D-glucose and D-mannose (D-glucose and D-galactose) are epimers (differ only at one chiral carbon) CHO OH H HO H HO H H OH CH 2 OH D-galactose CHO OH H HO H H OH H OH CH 2 OH D-glucose
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This note was uploaded on 07/07/2010 for the course CHEM 267 taught by Professor Fang during the Winter '09 term at Waterloo.

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12_Carbohydrate - Chem 267 Basic Organic Chemistry II Prof....

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