Carbohydrates Lecture Notes PDF

 Lecture 8: Carbohydrates Conform to the formula (CH2O)n Divided into Monosaccharides: - (CH2O)n where n = 3 to 7 - contain a single aldehyde or ketone; many hydroxyls - typically serve as fuel molecules for immediate consumption Polysaccharides: More than one aldehyde or keton...

 Lecture 8: Carbohydrates Conform to the formula (CH2O)n Divided into Monosaccharides: - (CH2O)n where n = 3 to 7 - contain a single aldehyde or ketone; many hydroxyls - typically serve as fuel molecules for immediate consumption Polysaccharides: More than one aldehyde or ketone - Often serve as storage form of carbohydrates  Aldoses vs. Ketoses I or the other monosacharides for - Sugars with an aldehyde functional group are aldoses - Sugars with an ketone functional group are ketoses  with 3 carbers Trioses - sugan one - only not that iral is 3 carbons Contain aldehyde (glyceraldehyde) or ketone (dihydroxyacetone) group  Note that the Carbon 2 of glyceraldehyde is chiral Stereoisomers ↑ The chiral carbon furthest from the carbonyl is the one which will determine if the sugar is named D * or L Arabinose is a diastereomer (stereoisomer but not mirror image of) of Ribose D- and L- ribose are enantiomers (mirror images) of one another. Select the carbon that determines whether this is D or L-Altrose U  A summary of some useful terms! time effect is minalities The D-Aldoses Note that they all have the OH of the carbon furthest from the aldehyde group on the right. That’s why they’re all “D”.  Taba The Aldehydes (in aldoses) react with an alcohol group to form a hemiacetal Ketones (in ketoses) react with an alcohol to form a hemiketal This is why longer monosaccharides cyclize  Monosaccharides with 5 or more carbons spend most of their time in cyclic structures. this is now chiral = > anomeric - carbon  aldos Ketoses Cyclization of the open form of D- C1 is called the glucose anomeric carbon –the Five membered α and β versions of D- ring called a glucose are anomers furanose; looks of one another. Once like furan; six the ring closes the membered = orientation of the OH pyranose. is fixed, unless the Drawn as a ring opens again (is in Haworth equilibrium with linear projection; the C1 form). becomes chiral and the OH can be Anomeric carbon in above (β) or below ketoses: C2. (α) the plane of the ring.  The various forms of monosaccharides undergo spontaneous mutarotation between the α and β and furan and pyran forms. Some are more stable than others, driven by steric constraints. it which at rateist recats with Ch Reactions of monosaccharides -Oxidation reduction (redox) -Isomerization -Esterification -Amino derivatives -Glycoside Formation  Oxidation-Reduction Alcohol  not a be sagan Oxidation of Glucose it das - not conform to sugan formula ↓ a - Sugar a not a Oxidation of the aldehyde group door yields aldonic acid aldelig tur Oxidation of the terminal CH2OH Ver group yields uronic acid Oxidation of both groups yields aldaric acid  Glycoside formation Reaction of the anomeric hydroxyl with hydroxyl groups (ROH) accompanied by elimination of water creates O-glycosidic bonds If the alcohol group is from another monosaccharide, one can make a disaccharide.  Distinguishing features of disaccharides: which2 menssucharides are v patting together e 1.Identity of monosaccharides. i.e. glucose + galactose = lactose. Glucose + glucose = maltose. 2.Carbons involved in linkage. i.e Carbon 1 to 2 in sucrose, 1 to 4 in lactose. 3.The order of two different monosaccharides. The sugar with a free anomeric carbon (i.e. a free aldehyde group when not cyclized) is reducible. This is called the reducing end; the other is the non-reducing end. 4.Configuration of the anomeric carbon: α or β? ba to is the a  If the ROH is the hydroxyl of another monosaccharide, you can make a disaccharide Free anomeric carbon: reducing end this is what makesit or If the hydroxyl group B in the reaction is in the α anomeric configuration, the new bond will be classified as α(1 4). These new S glycosidic bonds do not equilibrate; the α 3 or β configurations are locked into place. α- and β-Lactose (galactose with β1 to α or β glucose; has a β(1,4) linkage) Which OH’s orientation determines whether this is α or β lactose?  Other examples of disaccharides Sucrose: an α-glucose and a β-fructose joined by sured a an α(1,2) glycosidic bond. This is between the anomeric carbons; where is the reducing end?  Polysaccharides: -Homopolysaccharide: one repeating sugar -Heteropolysaccharide: two or more types -Oligosaccharide: polysaccharide with a small number of monosaccharide units (typically