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

42. Functions:
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

43. Starch and glycogen
Function: glucose storage
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

44. Glycogen:
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 nonreducing ends, but only ONE REDUCING END (only 1 free anomeric C, not tied up in glycosidic bond)

45. single free anomeric C = "reducing end" of polymer
Each molecule, including all the branches, has only ONE free anomeric C
single free anomeric C = "reducing end" of polymer
the only end capable of equilibrating with straight chain form of its sugar residue, which has free carbonyl C.

46. Which can then:
REDUCE (be oxidized by) an oxidizing agent like Cu2+

48. Cellulose and chitin
Function: STRUCTURAL, rigidity important
Cellulose:
homopolymer, b(1-> 4) linked glucose residues
cell walls of plants

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

50. 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

51. Carbohydrates all plant food milk carbohydrates are not equal
simple carbohydrates
complex carbohydrates

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

53. Complex Carbohydrates
starches and fibers
polysaccharides
chains of monosaccharides

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

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

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

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

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

59. Condensation making a disaccharide
chemical reaction linking 2 monosaccharides

60. 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

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

62. Maltose
2 glucose units
produced when starch breaks down
not abundant

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

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

65. Complex Carbohydrates
polysaccharides
glycogen and starch
built entirely of glucose
fiber
variety of monosaccharides and other carbohydrate derivatives

66. Glycogen limited in meat and not found in plants BUT
not an important dietary source of carbohydrate
BUT
all glucose is stored as glycogen
long chains allow for
hydrolysis and release
of energy

67. Starches
stored in plant cells
body hydrolyzes plant starch to glucose

68. Fiber structural parts of plants
found in all plant derived food
bonds of fibers cannot be broken down during the digestive process
minimal or no energy available

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

70. Fiber Characteristics
soluble fibers, viscous, fermentable
easily digested by bacteria in colon
associated with protection against heart disease and diabetes
lower cholesterol and glucose levels
found in legumes and fruits

71. Glucose Starch (branched) Glycogen Cellulose Starch (unbranched)
FIGURE 4-3: HOW GLUCOSE MOLECULES JOIN TO FORM POLYSACCHARIDES.
Starch (branched)
Glycogen
Cellulose
Starch (unbranched)
Fig. 4-3, p. 103

72. Fiber insoluble and not easily fermented promote bowel movements
alleviate constipation
found in grains and vegetables