Carbohydrates Structure and Function Sugar features 3 carbon

Carbohydrates: Structure and Function Sugar features • 3 carbon minimum; aldehyde or ketone present; (C H 2 O)n • Energy storage; lubricant; signaling

Carbohydrate Isomeric Forms H

D-Aldose Sugar Configurations Numbering begins at the carbonyl end of the sugar Penultimate carbon (pink) sets Lversus D-form

Isomer Classification Constitutional Isomers? Enantiomers? Diastereomers? Epimers? Anomers? What is the Enantiomer of D-Erythrose?

D-Ketose Sugar Configurations Carbonyl carbon (blue) is the anomeric carbon that generates two anomeric forms in the cyclic structure Anomeric carbon switches between an achiral and chiral form

Pyanose Formation by Intramolecular Linkage

Furanose Formation by Intramolecular Linkage Numbering via anomeric-carbon identification?

Fructose Isomers Anomeric Carbon Alpha – hydroxyl down Beta – hydroxyl up Isomer Options Constitutional or Stereo-isomers? Enantiomers or diastereoisomers? Epimers or anomers?

Carbohydrate Isomeric Forms H

Pictorial Representations of Glucose Cyclic form – Haworth project and chair configuration Linear form – Fisher projection Most abundant natural form? √ Why is only one configuration the most abundant form?

Corn Syrup and Honey Rich in Fructose Does this isomeric exactness really matter for enjoying life? ∆ Perceived as highly sweet Perceived as mildly sweet

Reducing Sugars - Reactive Aldehydes The protein modification referred to as advanced glycosylation end products (AGE) is implicated in aging, arteriosclerosis and diabetes Hemoglobin glycosylation is a high bloodsugar marker Experiment Benedict’s reagent Observation Inference Test solution + Benedict's Red ppt or green ppt or reagent; boil & cool. yellow ppt obtained Reducing sugar e. g. Glucose is present Test solution + Benedict's Solution remains clear reagent; boil & cool. Non-reducing sugar e. g. Sucrose is present

Disaccharide Biosynthesis via Glycosyltransferase Reaction

Alpha and Beta Assignments for Anomeric Carbons Only Why is frucofuranosyl labeled in a beta configuration?

Flipping a Box Upright On It’s Legs up shift to down Leg left shifts to right Left peg up stays up Legs in front stay front

Cellulose Straight Chains β-1, 4 Linkage Plant fiberforming structural polymer Most abundant organic compound in nature Dietary fiber; not digested except by bacteria

Glycogen and Starch Bent Chain α-1, 4 -Linkage Homopolymer for glucose storage Muscle/liver glycogen rich; 1, 6 branched linkage (1 in 10) Plant tissue with amylose (unbranched) & amylopectin (1 in 30 branching)

Glycoproteins – Carbohydrates Attached to Proteins More protein than carbohydrate N-linked via Asn or O-linked via Ser or Thr Chemical signature for protein or whole cell surfaces

Glycosylation of Extracellular Proteins Red blood cell stimulatory hormone: erythropoietin (EPO) Glycosylation enhances stability Endurance athletes illegally use to increase oxygencarrying capacity EPO spiking-detection based on glycosylation patterns

Modified Saccharides N- O- C-glycosidic linkages Increase biochemical versatility (e. g. chemical signaling)

Glycosaminoglycan Structural Units Chitin: N-acetylglucosamine homopolymer Present in insect, crustacean, and arachnid exoskeleton Second most abundant polysaccharide in nature

Glycosaminoglycan Heteropolymers Glucosamine/galactosamine amino sugar derivatives Repeating disaccharide units with negatively charged group

Proteoglycans – Polysaccharides & Proteins Lubricants , structural components, and cell adhesion Cartilage – collagen (strength) and agrecans (shock absorber) More polysaccharide than protein

Chapter 11 Problems: 1, 3, 5, 7, 9, 13, 15, 17, 19, 27 and 31