1. Chapter 8 (part 1)
Carbohydrates

2. Carbohydrates Most abundant class of biological molecules on Earth
Originally produced through CO2 fixation during photosynthesis

3. Roles of Carbohydrates
Energy storage (glycogen,starch)
Structural components (cellulose,chitin)
Cellular recognition
Carbohydrate derivatives include DNA, RNA, co-factors, glycoproteins, glycolipids

4. Carbohydrates
Monosaccharides (simple sugars) cannot be broken down into simpler sugars under mild conditions
Oligosaccharides = "a few" - usually 2 to 10
Polysaccharides are polymers of the simple sugars

5. Monosaccharides Polyhydroxy ketones (ketoses) and aldehydes (aldoses)
Aldoses and ketoses contain aldehyde and ketone functions, respectively
Ketose named for “equivalent aldose” + “ul” inserted
Triose, tetrose, etc. denotes number of carbons
Empirical formula = (CH2O)n

6. Monosaccharides are chiral
Aldoses with 3C or more and ketoses with 4C or more are chiral
The number of chiral carbons present in a ketose is always one less than the number found in the same length aldose
Number of possible steroisomers = 2n (n = the number of chiral carbons)

7. Stereochemistry Enantiomers = mirror images
Pairs of isomers that have opposite configurations at one or more chiral centers but are NOT mirror images are diastereomers
Epimers = Two sugars that differ in configuration at only one chiral center

8. Cyclization of aldose and ketoses introduces additional chiral center
Aldose sugars (glucose) can cyclize to form a cyclic hemiacetal
Ketose sugars (fructose) can cyclize to form a cyclic hemiketal

9. Haworth Projections -OH up = beta -OH down = alpha 6 5 4 1 2 3
Anomeric carbon
(most oxidized)
For all non-anomeric carbons, -OH groups point down in Haworth projections if pointing right in Fischer projections

10. Monosaccharides can cyclize to form Pyranose / Furanose forms
b = 36%
a = 21.5%
b = 58.5%
a = 13.5%
b = 6.5%

11. Conformation of Monosaccharides
Pyranose sugars not planar molecules, prefer to be in either of the two chair conformations.

12. Reducing Sugars
When in the uncyclized form, monosaccharides act as reducing agents.
Free carbonyl group from aldoses or ketoses can reduce Cu2+ and Ag+ ions to insoluble products

14. Derivatives of Monosaccharides

15. Sugar Phosphates

16. Deoxy Acids

17. Amino Sugars

18. Sugar alcohols

19. Monosaccharide structures you need to know
Glucose
Fructose
Ribulose
Glyceraldehyde
Dihydroxyacetone