CHAPTER 7 Carbohydrates hydrates of carbons most abund ending determined by highest asymmetrical carbon 3 triose 4 tetrose 5 pentose 6 hexose Ketose Aldose most natural carbs are D 1 Carbonyl carbon 2 Asymmetric carbons 3 Carbon Numbering 4 D vs L configuration Aldose contains aldehyde group CHO Glyceraldehyde simple aldose Ketose contains ketone group C O dihydroxyacetone simple ketose D L enantiomers of each other Enantiomers mirror images of each other Disasteroisomers different configurations at one or more but not all of the equivalent stereocenters Anomers have a different configuration only about the anomeric carbon atom Epimers are disasteromers that differ in configuration of only one stereogenic center Cyclize become cyclo intramolecular reaction ex D glucose cyclic hemiacetal ex D fructose cyclic hemiketal simple sugars can cyclize two ways 1 furanose structures pentagon chair boat most common chair boat 2 pyranose structures hexagon envelope test Axial and Equatorial Groups slide 14 b D glucose most widely occurring organic group in nature Derivatives of Simple Sugars 1 Sugar Acids free anomeric carbon is reducing agent these are reducing sugars Test for glucose in urine and blood are based on cuprous oxide precipitate reducing sugar sugar that has a free anameric carbon That can participate in a rxn as an acid can donate protons 2 Sugar Alcohols result from mild reduction of carbonyl group can t cyclize like regular aldoses and ketoses taste sweet so some used as sweeteners can t metabolize them 3 Deoxy Sugars Lost 1 or more OH groups replaced with H Found in DNA glucoproteins cell wall polysaccharides deoxy replacing a hydroxyl group with a Hydrogen 4 Sugar Esters Phosphate esters are especially important Activated sugars key metabolic intermediates important in metabolism 5 Amino sugars found in Glycoproteins N O linked saccharides ECM bacterial cell wall yeast and insect walls chitin ex D glucosamine and Dgalactosamine Sugar Polymers a Monosaccharides single sugar molecules simple sugars functional unit of oligo and polysaccharides b Sugar Polymers Can be directional reducing end non reducing end main but not only linkage is Glycosidic bond Oligosaccharides Contain covalently linked oligosaccharides antibiotics glycolipids glycoproteins a O linked Oligosaccharides a Linked to OH on Ser Thr hydroxyK b Most 1 4 sugars b N Linked Oligosaccharides a Linked to NH2 on Asn b 5 sugars c Conserved structure of 5 sugars reducing sugar contain aldehyde groups that can be oxidized to carboxylic acids The reactive aldehyde must be free that is available to do the chemistry is in the open chain form after aldehyde is oxidized becomes a sugar with free anomeric carbon that can act as an acid http guweb2 gonzaga edu faculty cronk biochem C index cfm definition carbohydrate