1. Sugars
Alice Skoumalová

2. Repetition:
Glucose, fructose and galactose (structure)
Optical isomerism - definition (D- and L-glucose)
Formation of a cyclic glucose (anomers)
Reducing sugars - definition
The most important disaccharides (composition)
The most important polysaccharides (structure)

3. Important sugars in an organism:
1. Glucose
2. Glycogen
3. Glycoproteins
4. Glycolipids
5. Proteoglycans

4. An introduction to carbohydrates:
a large class of naturally occurring polyhydroxy aldehydes and ketones
monosaccharides (simple sugars): from 3 to 7 carbons + one aldehyde or ketone functional group
chiral compounds (having right- or left-handedness with two different mirror-image forms) because they contain carbons bonded to four different groups
An aldose
A ketose
Monosaccharides, disaccharides, polysaccharides
Modified saccharides

5. The D and L families of sugars:
Enantiomers - „mirror images“ (rotate polarized light in opposite directions → optical activity)
Fischer projection:
a mirror
D sugar → the OH group on the chiral carbon farthest from the carbonyl group pointing to the right in a Fischer projection
L sugar → the OH group on the chiral carbon farthest from the carbonyl group pointing to the right in a Fischer projection
2n of possible stereoisomers (half that many pairs of enantiomers)
n - the number of chiral carbons (e.g. glucose - 16 stereoisomers)

6. The structure of glucose:
Mutarotation
change in rotation of plane-polarized light resulting from the equilibrium between cyclic anomers and the open-chain form of a sugar
Anomers
cyclic sugars that differ only in positions of substituents at the anomeric carbon

7. Reactions of the monosaccharides:

8. Reaction with oxidizing agents:
Reducing sugars react in basic solution with a mild oxidizing agent
In basic solutions, all monosaccharides are reducing sugars

9. Reaction with alcohols (glycoside formation):
Glycosidic bond → bond between the anomeric carbon of a monosaccharide and an -OR group
Hydrolysis of a disaccharide (during digestion of carbohydrates)

10. Important monosaccharides Aldoses:
Pentoses
in RNA and NADH
in polysaccharides in the walls of plant cells
Hexoses
„blood“ sugar (energy)
in cellulose and starch
in glycogen (as a source of energy in an organism)
in glycolipids and glycoproteins
in lactose (milk), glycolipids and glycoproteins
converted to glucose
galactosemia

11. Ketoses: Deoxyaldoses: D-Ribulose D-Fructose 2-deoxy-D-ribose
an intermediate in the pentose phoshate pathway
in fruit juices and in honey
in sucrose
converted to glucose
Deoxyaldoses:
2-deoxy-D-ribose
in DNA

12. Acetylated amino sugars:
N-Acetyl-D-glucosamine
N-Acetyl-D-galactosamine
in glycoproteins
Acidic sugars:
D-Glucuronic acid
N-Acetylneuraminic acid (sialic)
in glycosaminoglycans in connective tissue
conjugation of bile acids
in glycoproteins

13. Important disaccharides
Sucrose
Maltose
a breakdown product of the starch
cane sugar, beet sugar
non-reducing sugar
Lactose
milk sugar (4,5% - 7%)
lactose intolerance (reduced activity of lactase)

14. Important polysaccharides
Cellulose
ß-D-Glucose, ß-1,4 link
the fibrous substance that provides structure in plants
humans cannot hydrolyze cellulose

15. 1. Amylose (20%, soluble in water)
Starch
α-D-Glucose
source of energy in plants
fully digestible - an essential part of the human diet (the grains wheat, potatoes, rice)
1. Amylose (20%, soluble in water)
α-1,4 link
2. Amylopectin (80%, not water soluble)
α-1,6 branches (every 25 units)

16. Glycogen
α-D-Glukose, α-1,4 and α-1,6 link
source of energy in animals (liver, muscles)

17. Other important sugars 1. Glycosaminoglycans
Hyaluronic acid
25,000 disaccharide units
form very viscous mixture
in connective tissue, synovial fluid, vitreous humour
Chondroitin sulfate
in tendons and cartilage
Glucuronic acid
N-Acetylgalactosamine sulfate
N-Acetylglucosamine
Glucuronic acid

18. Heparin
contains sulfate groups (negative charges)
anticoagulant - prevents the clotting of blood (binds to the clotting factors)

19. 2. Proteoglycans
aggregates of proteins and glycosaminoglycans in the extracellular matrix
highly hydrated and resilient (cartilage)

20. 3. Glycoproteins on the surfaces of cells (receptors, blood type)
Forms:

21. Blood type
cell-surface carbohydrates

22. Summary:
Epimers, enantiomers, anomers (examples)
The most important reaction of monosaccharides
The importance of glucose
Important disaccharides
Important polysaccharides
Glycosaminoglycans and proteoglycans - structure, function
Glycoproteins - structure, function