1. Carbohydrates Biochemistry
Dr. Marcelus U. Ajonina

2. outcomes: By the end of this modules, students are expected to:
State the importance of carbohydrates
Understand the importance of carbohydrates
Attempt the classification of carbohydrates

3. outcomes: By the end of this modules, students are expected to:
Understand Isomerism in CHO
Disorders of CHO
Differentiate between structural and storage polysaccharides; homo and heteropolysaccharides, etc

4. Definition Carbohydrates literally mean hydrates of carbon.
hydrates ( water).
Because it was thought to have the molecular formula (CH2O)n, the ratio of H to O as in water (H2O) hence the name.
Carbohydrates also referred to Polysaccharides (Sweet)
Not all carbohydrates obey this rule. (e.g,derivative)

5. Biochemical Definition
Carbohydrates are poly-hydroxy carbonyl compounds (aldehyde or ketone) and their derivative and the polymer that give them on hydrolysis Example:

6. BIOMEDICAL IMPORTANCE
Carbohydrates have important structural and metabolic roles.
Glucose is the most important carbohydrate
most dietary carbohydrate is absorbed into the blood stream as glucose.
Glucose is the major metabolic fuel of mammals
a universal fuel of the fetus

7. Biomedical Importance of Carbohydrates
1- Energy source for plants and animals (glucose). One of the major source of energy in cell. 75% of energy in cell comes from CHO. 25% from others (fats) 1 g CHO =4 K.calories 1 g protein =4 K.calories. 1 g lipid =9K.calories. Why body not use lipid as major energy source instead of CHO?

8. 2- Cell membrane components: eg
2- Cell membrane components: eg. Glycolipid and glycoprotein 3- Form structural tissues in plants and in microorganisms eg. (cellulose, chitin, murein) 4- Glucose is the precursor for synthesis of all other carbohydrates in the body, including Galactose in lactose of milk.

9. 5-To describe the mechanism of some diseases related to CHO.
Glycogen for storage; .
Store as glycogen in animals, and starch
In plants. (storage form of energy).
Why the cell store excess glucose as glycogen?
Ribose and Deoxyribose in nucleic acids;
DNA –deoxy ribonucleic acid (deoxy sugar)
RNA –ribonucleic acid (ribose sugar). .
5-To describe the mechanism of some diseases related to CHO.
eg.Diabetes Mellitus.
lactose intolerance, Glycogen storage diseases
glactosemia . ,

10. Classification of Carbohydrates
Carbohydrates are classified into four groups:
1.Monosaccharides: (saccharides means sugars)that cannot be hydrolyzed into simpler carbohydrates, (Exp. Glucose).
2.Disaccharides: condensation products of two monosaccharide units (Exp. Lactose).
Note, all mono and disaccharides have the ending ose (glucose, galactose, ribose, lactose, etc…)

11. Classification of Carbohydrates
3.Oligosaccharides are condensation products of three to ten monosaccharides; Maltotriose is an example.
4.Polysaccharides are condensation products of more than ten monosaccharide units (Exp. Glycogen & Starch).

12. Monosaccharides are classified by:
1- the number of carbon atoms:
3C-Triose , 4C -tetroses , 5C-pentoses , 6C- hexoses and 7C – heptoses.
2-the position or type of carbonyl group:
Aldehyde, aldose (terminal)
Ketone, ketose (middle ).
3- Both number of carbon atom and type of carbonyl
E,g Aldotriose and Ketotriose

13. Monosaccharides are classified by: 1- the number of carbon atoms:

14. Aldose sugars

15. Ketose sugars

16. Monosaccharides Glucose Structure
The structure of Glucose can be represented in three ways:
Straight Chain Form Haworth Projection Chair Form

17. Monosaccharides isomers of glucose

18. Monosaccharides isomers of glucose

20. Cyclic Fischer Projection of a-D-Glucose
Haworth Projection of a-D-Glucose

21. Almost all monosaccharides (except
dihydroxy acetone DHA )contain at least one asymmetrical carbon atom (chiral Centre) and are, therefore, have optical activity (ability to rotate plane polarized light) and optical isomers.
The number of isomers is obtained by the formula 2n
n=No of asymmetric carbons atom.

22. Monosaccharides Forms of Isomerism
Monosaccharides exhibit various forms of isomerism: Because it have asymmetric carbon atom
Isomerism is the phenomenon in which more than one compounds have the same chemical formula but different chemical structures.

23. Isomerism
Chemical compounds that have identical chemical formulae but differ in properties and the arrangement of atoms in the molecule are called isomers.

24. Isomerism

25. Isomerism
Geometric
Cahn-Ingold-Prelog priority rules (CIP priority rules)
The Zusammen/Entgegen System

26. Stereoisomerism (Optical)
D and L Enantiomers.
Pyranose and Furanose ring structures.
Alpha and Beta anomers.
Epimers.
Aldose and Ketose isomerism.
Optical activity

27. 1- D & L isomers (enantiomers)
Those monosaccharides that are of physiological significance exist in the D- configuration, where the hydroxyl group is on the right side .
The mirror-image, called enantiomers, are in the L-configuration.
They are related to glyceraldehyde which exists in
two isomers D and L

28. Monosaccharides L and D Enantiomers
It also called mirror images or Optical Isomers:

29. Monosaccharides can exist in either of two configurations, as determined by the orientation of the hydroxyl group about the asymmetric carbon farthest from the carbonyl group.
e,g D & L form of glucose is determine by carbon 5.

30. Monosaccharides L and D Enantiomers

31. 2-pyranose and furanose ring (isomer)
Monosaccharide with 5 or 6 carbon atoms tend to cyclyze in solution.
This terminology indicate that the ring structure of monosaccharide is similar to either pyran or furan

32. Monosaccharides 2-Pyranose and Furanose

33. 3 - α- and β anomers (isomers)
Isomers that differ on the position of OH
group around anomeric carbon (which was
carbonyl carbon) when the ring is formed.

34. Monosaccharides 3-Alpha and Beta Anomers

35. 3-Epimers (isomers)
Two monosaccharide that differ from each other by position of OH group on one carbon. ( eg carbon 2,3 and 4 of glucose).
glucose and galactose are epimers at carbon 4
While glucose and mannose are carbon 2 epimers.

36. Monosaccharides Epimers
Mannose Glucose Galactose

38. Monosaccharides 5-Aldose and Ketose Isomerism

39. Optical activity
The ability to rotate plane-polarized light to the right (dextrorotatory) +sign
Or to the left (levorotatory) - sign
Glucose is dexrtoratotry hence the name
dextrose in clinical practice eg IV fluid
Fructose is levorotatory hence the name levulose

40. Monosaccharides Physiological Importance
Pentoses of Physiologic importance
Ribose inter the structure of Nucleic Acids
Ribose Deoxyribose

41. Monosaccharides Physiological Importance
Hexoses of Physiologic importance:
Glucose .
Fructose
Galactose .

42. Common names: Natural Source: glucose, grape sugar, dextrose
D-glucose
Common names:
glucose, grape sugar, dextrose
Natural Source:
Fruits,,cereal starch hydrolysis, sugar
hydrolysis, corn syrup and honey.

43. D-glucose Importance:
the sugar of the body, the principal one used by the tissue.
Building block for: disaccharides (such as sucrose, lactose and maltose) and polysaccharides (starch, cellulose and glycogen) converted to ribose and deoxyribose for DNA and RNA synthesis.

44. Formed by hydrolysis of lactose (milk sugar).
D-galactose
Natural Source:
None for free form
Formed by hydrolysis of lactose (milk sugar).
Importance: converted to glucose, and used for the synthesis of Milk.
enter in cellular membranes of brain & nervous system.

45. Enzyme to metabolize galactose missing and levels build in blood cause
D-galactose
Deficiency diseases:
Galactosemia:
Enzyme to metabolize galactose missing and levels build in blood cause
mental retardation,
cataracts and
cirrhosis.

46. Levulose and fruit sugar Natural Source: Fruit juice and honey
D-fructose
Common names:
Levulose and fruit sugar
Natural Source:
Fruit juice and honey
Hydrolysis of cane and beat sugar
Importance: converted to glucose in liver, source of energy for spermatozoa
Due to sweetness, used as sweetener.

48. Glycosides Glycoside is two substances connected by glycosidic bond.
Importance:
1- formation of disaccharide and other derivative.
2- cardiac glycoside (is a drug used in treatment of some heart disease)by inhibiting Na-K ATPase pump. e.g Digitalis &.Auobain (contain sugar and steroid)
3-Certain antibiotic like streptomycin.

49. The physiologically important disaccharides are
Maltose , Sucrose, and Lactose:

50. Disaccharides Formation

51. Disaccharides Maltose
Maltose : Malt sugar, composed exclusively of glucose, found in germinating cereals and malts
The major degradation product of starch, is composed of 2 glucose monomers in an α- (1,4) glycosidic bond.
Give Glucose + glucose by maltase enzyme. .

52. Disaccharides Maltose

53. Disaccharides Sucrose
Sucrose: table sugar, found in cane and beat sugar
composed of glucose and fructose through an α-(1,2)b-glycosidic bond.
give Glucose + fructose by sucrase enzyme(invertase) because the product of its hydrolysis (known as invert sugar) invert optical activity from dextro to levorotatory.

54. Disaccharides Sucrose

55. Disaccharides Lactose
Lactose: Milk sugar , is found exclusively in the milk of mammals and consists of galactose and glucose in a β-(1,4) glycosidic bond
give Glucose + galactose by lactase enzyme

56. Disaccharides Lactose

57. Lactose Intolerance Symptoms
Bloating, abdominal discomfort, and diarrhea
Causes
Lactase deficiency
Oligosacchrides
Usually not found free but in the form of glycoprotein and glycolipid.few e,g maltotriose and raffinose.

58. Sucrose: prevalent in sugar cane and sugar beets, is composed of glucose and fructose through an α-(1,2)b-glycosidic bond.
Lactose: is found exclusively in the milk of mammals and consists of galactose and glucose in a β-(1,4) glycosidic bond

59. Maltose: the major degradation product of starch, is composed of 2 glucose monomers in an α-(1,4) glycosidic bond.

60. Classification of polysaccharide
When polysaccharides are composed of a single monosaccharide building block, they are termed homopolysaccharides.
They are Branched or unbranched
Storage or structural
Polysaccharides composed of more than one type of monosaccharide are termed heteropolysaccharides

61. Polysaccharides Types
Homopolysaccharides
Unbranched Branched

62. Polysaccharides Starch
Is a homopolymer of Glucose. (storage form of CHO in plant)
It is the most abundant carbohydrate in cereals, potatoes, and other vegetables .
The two main constituents are amylose (15– 20%), which has a non-branching helical structure.
and amylopectin (80–85%), which consists of branched chains composed of 24–30 glucose residues united by → 4 linkages in the chains and by 1 → 6 linkages at the branch points.

63. Polysaccharides Starch (Amylopectin)

64. Polysaccharides Glycogen
Is the storage polysaccharide in human.
Is a highly branched than amylopectin

65. Glycogen is the major form of stored carbohydrate in animals.
It is a homopolymer of glucose in α- (1,4) linkage;
it is highly branched, with α-(1,6) branch linkages occurring every residues.

66. Glycogen is a very compact structure .
This compactness allows large amounts of carbon energy to be stored in a small volume, with little effect on cellular osmolarity.

67. Glycogen is primarily stored in liver and muscles.
Liver glycogen contributes to maintenance of blood glucose level
Muscle glycogen is used as readily available source of energy within muscles during exercise

69. Polysaccharides Glycogen (General Structure)

70. Polysaccharides Glycogen (Branch Point)

71. Polysaccharides Others
Inulin is a homopolysaccharide of fructose, linked by β(1-2) glycosidic bond.
found in tubers and roots of artichoke ( used for assessment of glomerular filtration rates .

72. Cellulose: is the chief insoluble constituent of plants framework.
It consists of β-D-glucopyranose units linked by β(1 → 4) bonds to form long, straight chains.
Cellulose cannot be digested by human because of the absence of an enzyme that hydrolyzes the β linkage.
There is limited bacterial metabolism of cellulose in the human colon
It is an important source of “bulk” and Fibers in the diet (which attract water and soften stool hence prevent constipation)