Nov21Lect - Carbohydrates 1 Week 11 Monosaccharides...

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Week 11 Carbohydrates 1
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Week 11 Monosaccharides 2 Monosaccharides are classified by their number of carbon atoms: Hexose Heptose Octose Triose Tetrose Pentose Formula Name C 3 H 6 O 3 C 4 H 8 O 4 C 5 H 10 O 5 C 6 H 12 O 6 C 7 H 14 O 7 C 8 H 16 O 8
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Week 11 Monosaccharides 3 There are only two trioses: Often the designations aldo- and keto- are omitted and these compounds are referred to simply as trioses, tetroses, and so forth. Although these designations do not tell the nature of the carbonyl group, they at least tell the number of carbons. Dihydroxyacetone (a ketotriose) Glyceraldehyde (an aldotriose) CHO CHOH CH 2 OH 2 C=O 2
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Week 11 Monosaccharides 4 Glyceraldehyde contains a stereocenter and exists as a pair of enantiomers. CHO C H OH CH 2 OH CHO C 2 OH H HO ( S )-Glyceraldehyde ( R )-Glyceraldehyde
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Week 11 Fischer Projections 5 C CHO CH 2 OH OH H CHO CH 2 OH H ( R )-Glyceraldehyde (three-dimensional representation) convert to a Fischer projection . ( R )-Glyceraldehyde (Fischer projection)
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Week 11 D,L Monosaccharides 6 In 1891, Emil Fischer made the arbitrary assignments of D- and L- to the enantiomers of glyceraldehyde. CHO H OH CH 2 2 H HO D D L-Glyceraldehyde (S)-Glyceraldehyde D-Glyceraldehyde (R)-Glyceraldehyde [ α ] 25 = +13.5 [ α ] 25 = -13.5
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Week 11 D,L Monosaccharides 7
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Week 11 D,L Monosaccharides 8 Here are the two most abundant D-aldotetroses and the two most abundant D-aldopentoses in the biological world: D-Erythrose D-Threose D-Ribose 2-Deoxy-D- ribose CH 2 OH CHO H H 2 H HO H 2 H H 2 H H H H H
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Week 11 D,L Monosaccharides 9 And the three most abundant hexoses: CHO H OH H HO OH H CH 2 OH OH H H HO CH 2 OH OH H CHO H OH H HO CH 2 OH H HO C OH H CH 2 OH OH H O D-Fru ctose D-Glu cose D-Galactose
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Week 11 Amino Sugars 10 CHO OH OH H NH 2 H H HO H CH 2 OH CHO OH OH H H H H HO H 2 N CH 2 OH CHO OH OH H NHCCH 3 H H HO H CH 2 OH O CHO OH H H 2 H HO HO H 2 D-Glucosamine D-Galactosamine N -Acetyl-D- glucosamine 4 2 D-Mannosamine
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Week 11 Aldohexoses 11
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Week 11 Aldohexoses - continued 12
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Week 11 Physical Properties 13 Monosaccharides are colorless crystalline solids, very soluble in water, but only slightly soluble in ethanol. sweetness relative to sucrose: Carbohydrate Fructose Glucose Galactose Sucrose (table sugar) Lactose (milk sugar) Honey Sweetness Relative to Sucrose 1.74 1.00 0.97 0.74 0.32 0.16 Invert sugar 1.25 Artificial Sweetener Sweetness Relative to Sucrose Maltose 0.33 Saccharin 450 Acesulfame-K 200 Aspartame 160
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Week 11 Cyclic Structure 14
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Week 11 Haworth Projections 15 Haworth projections Five- and six-membered hemiacetals are represented as planar pentagons or hexagons, as the case may be, viewed through the edge. They are most commonly written with the anomeric carbon on the right and the hemiacetal oxygen to the back right.
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Nov21Lect - Carbohydrates 1 Week 11 Monosaccharides...

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