1. CARBOHYDRATE CHEMISTRY

2. Introduction Carbohydrates are one of the three major
classes of biological molecules.
Carbohydrates are also the most abundant biological molecules.
Carbohydrates derive their name from the
general formula Cn (H2O).

3. functions Variety of important functions in living systems:
nutritional (energy storage, fuels, metabolic intermediates)
structural (components of nucleotides, plant and bacterial cell walls, arthropod exoskeletons, animal connective tissue)

4. informational (cell surface of eukaryotes -- molecular recognition, cell-cell communication)
osmotic pressure regulation (bacteria)

5. Carbohydrates are carbon compounds that contain large quantities of hydroxyl groups.

6. Carbohydrates are chemically characterized as:
Poly hydroxy aldehydes or
Poly hydroxy ketones.

7. Sugars that contain an aldehyde group are called Aldoses.
Sugars that contain a keto group are called Ketoses.

9. classification All carbohydrates can be classified as either:
Monosaccharides
Disaccharides
oligosaccharides or Polysaccharides.

10. Monosaccharides- one unit of carbohydrate
Disaccharides- Two units of carbohydrates.
Anywhere from two to ten monosaccharide units, make up an oligosaccharide.
Polysaccharides are much larger, containing hundreds of monosaccharide units.

11. Carbohydrates also can combine with lipids to form glycolipids
With proteins to form glycoproteins.

12. Isomers
Isomers are molecules that have the same molecular formula, but have a different arrangement of the atoms in space. (different structures).
For example, a molecule with the formula AB2C2, has two ways it can be drawn:

13. Isomer 1

14. Isomer 2

16. Examples of isomers:
Glucose
Fructose
Galactose
Mannose
Same chemical formula C6 H12 O6

17. EPIMERS
EPIMERS are sugars that differ in configuration at ONLY 1 POSITION.

18. Examples of epimers :
D-glucose & D-galactose (epimeric at C4)
D-glucose & D-mannose (epimeric at C2)
D-idose & L-glucose (epimeric at C5)

21. ENANTIOMERS
Non-Superimposable COMPLETE mirror image (differ in configuration at EVERY CHIRAL CENTER.

22. The two members of the pair are designated as D and L forms.
In D form the OH group on the asymmetric carbon is on the right.
In L form the OH group is on the left side.
D-glucose and L-glucose are enantiomers:

27. Asymmetric carbon
A carbon linked to four different atoms or groups farthest from the carbonyl carbon
Also called Chiral carbon

29. cyclization Less then 1%of CHO exist in an open chain form.
Predominantly found in ring form.
involving reaction of C-5 OH group with the C-1 aldehyde group or C-2 of keto group.

30. Six membered ring structures are called Pyranoses .
five membered ring structures are called Furanoses .

32. Anomeric carbon
The carbonyl carbon after cyclization becomes the anomeric carbon.
This creates α and β configuration.
In α configuration the OH is on the same of the ring in fischer projection. In Haworths it is on the trans side of CH2OH.

35. Such α and β configuration are called diastereomers and they are not mirror images.
Enzymes can distinguished between these two forms:
Glycogen is synthesized from α-D glucopyranose
Cellulose is synthesized from β -D glucopyranose

36. MUTAROTATION
Unlike the other stereoisomeric forms, α and β anomers spontaneously interconvert in solution.
This is called mutarotation.

39. Optical Activity
When a plane polarized light is passed through a solution containing monosaccharides the light will either be rotated towards right or left.
This rotation is because of the presence of asymmetric carbon atom.
If it is rotated towards left- levorotatory (-)
If it is rotated towards right- dextrorotatory(+)

40. Reducing sugar
Sugars in which the oxygen of the anomeric carbon is free and not attached to any other structure, such sugars can act as reducing agents and are called reducing sugars.

41. Carbohydrates
glucose provides energy for the brain and ½ of energy for muscles and tissues
glycogen is stored glucose
glucose is immediate energy
glycogen is reserve energy

42. Classes of Carbohydrates
simple carbohydrates
complex carbohydrates

43. Simple Carbohydrates sugars monosaccharides – single sugars
disaccharides – 2 monosaccharides

44. Complex Carbohydrates
polysaccharides
e.g. starches and fibers
chains of monosaccharides

45. Simple Carbs monosaccharides all are 6 carbon hexes
6 carbons
12 hydrogens
6 oxygens
arrangement differs
accounts for varying sweetness
glucose, fructose, galactose

46. Glucose mild sweet flavor known as blood sugar essential energy source
found in every disaccharide and polysaccharide

47. Fructose sweetest sugar found in fruits and honey
added to soft drinks, cereals, deserts

48. Galactose
hardly tastes sweet
rarely found naturally as a single sugar

49. Disaccharides pairs of the monosaccharides glucose is always present
2nd of the pair could be fructose, galactose or another glucose
Joined by condensation
Separated by hydrolysis
hydrolysis and condensation occur with all energy nutrients
maltose, sucrose, lactose

50. Three types of monosaccharides…
fructose
glucose
galactosea
Three types of monosaccharides…
…join together to make three types of disaccharides.
sucrose
maltose
lactose
FIGURE 4-2: HOW MONOSACCHARIDES JOIN TO FORM DISACCHARIDES.
(fructose-glucose)
(glucose-glucose)
(glucose-galactose)
aGalactose does not occur in foods singly but only as part of lactose.
Fig. 4-2a, p. 101

51. Condensation making a disaccharide
Condensation reaction linking 2 monosaccharide

52. Hydrolysis breaking a disaccharide water molecule splits
occurs during digestion

53. Maltose 2 glucose units produced when starch breaks down not abundant
 1-4 glycosidic bond

54. Sucrose fructose and glucose tastes sweet
fruit, vegetables, grains
table sugar is refined sugarcane and sugar beets
brown, white, powdered

55. Lactose glucose and galactose main carbohydrate in milk
known as milk sugar

57. Complex Carbohydrates
polysaccharides
Storage polysaccharides
built entirely of glucose
Glycogen and starch
Structural polysaccharides
May have some modified sugars
Cellulose and chitin

58. Polysaccharides 2 types:
HOMOpolysaccharides (all 1 type of monomer), e.g., glycogen, starch, cellulose, chitin
HETEROpolysaccharides (different types of monomers), e.g., peptidoglycans, glycosaminoglycans

59. Functions of Polysaccharides
glucose storage (glycogen in animals & bacteria, starch in plants)
structure (cellulose, chitin, peptidoglycans, glycosaminoglycans
information (cell surface oligo- and polysaccharides, on proteins/glycoproteins and on lipids/glycolipids)
osmotic regulation

60. Starch Function: glucose storage in plants Starch -- 2 forms:
amylose: linear polymer of a(1-> 4) linked glucose residues
amylopectin: branched polymer of a(1-> 4) linked glucose residues with a(1-> 6) linked branches

62. . Glycogen Glycogen stored glucose in animals
branched polymer of a(1-> 4) linked glucose residues with a(1-> 6) linked branches
like amylopectin but even more highly branched and more compact
branches increase H2O-solubility
Branched structures: many non-reducing ends, but only ONE REDUCING END (only 1 free anomeric C, not tied up in glycosidic bond)

63. Cellulose STRUCTURAL, rigidity important
homopolymer, b(1-> 4) linked glucose residues
cell walls of plants

64. Chitin:
homopolymer, b(1-> 4) linked N-acetylglucosamine residues
hard exoskeletons (shells) of arthropods
(e.g., insects, lobsters and crabs)

65. Fiber structural parts of plants
found in all plant derived food
Also called indigestible complex carbohydrates
bonds of fibers cannot be broken down during the digestive process
minimal or no energy available

66. Fiber types pectins lignins resistant starches cellulose
classified as fibers
escape digestion and absorption

67. NEXT CLASS
OLIGOSACCHARIDES AND THEIR MEDICAL IMPORTANCE
METABOLISM