1. Carbohydrates: Structure and Function
Sugar features
3 carbon minimum; aldehyde or ketone present; (C H2O)n
Energy storage; lubricant; signaling

2. Carbohydrate Isomeric Forms

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

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

5. 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

6. Pyanose Formation by Intramolecular Linkage

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

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

9. Carbohydrate Isomeric Forms

10. 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?

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

12. 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 blood-
sugar marker
Benedict’s reagent
Experiment
Observation
Inference
Test solution + Benedict's reagent; boil & cool.
Red ppt or green ppt or yellow ppt obtained
Reducing sugar e.g. Glucose is present
Solution remains clear
Non-reducing sugar e.g. Sucrose is present

13. Disaccharide Biosynthesis via Glycosyltransferase Reaction

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

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

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

17. 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)

18. 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

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

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

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

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

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

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