1. CARBOHYDRATES Foundation Module-Phase 1 Department of Biochemistry
Faculty of Medical Sciences

2. What are carbohydrates?
Aldehyde or ketone derivatives of polyhydric alcohol
Formula (CH2O)n (n > 3)
Not all carbohydrates have this empirical formula: deoxysugars, aminosugars
used as an energy source and in making cell structures.
Energy

3. Sources of carbohydrate
Biscuit
Rice
Bread
Potato
Wheat
Oats

4. Do you know…. Q1: List the main functions of carbohydrates?
Q2: How are carbohydrates classified?
Answer
Answer

5. Types of Carbohydrates
Based on the number of monomers.
Monosaccharides: 1
Disaccharides: 2
Oligosaccharides: 3-20
Polysaccharides: more than 20
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6. Q3: How to classify monosaccharides?
According to the number of carbons
According to functional groups
Aldosugars
Ketosugars

7. Back

8. Back

9. Monosaccharide
Structure
(Single Sugar Unit)

10. Common Monosaccharides
fructose (fruit sugar)
galactose
For your interest only
How to measure Glucose

11. Properties of monosaccharides?
A. Physical properties * Highly soluble in water * Most taste sweet  
B. Chemical properties * Formation of cyclic hemiacetals or hemiketals            * New chiral center => 2 “anomers”
designated a and b

12. groups C

13. 3 1 2 4 5 6
Answers

15. Chiral centers v
Penultimate OH group

17. Structural representation of sugars
Haworth projection
Fisher projection
(straight chain representation)
(simple ring in perspective)

18. Haworth projection
Fisher projection

19. Disaccharides
Sugars composed of two monosaccharides linked together by glycosidic bonds.
e.g.Maltose

20. Common Disaccharides sucrose (table sugar)
Commercially obtained from sugar cane or sugar beet

21. maltose (seed sugar) Used : as a nutrient (malt extract)
(1,4) linkage
Found in germinating grains
Used :
as a nutrient (malt extract)
as a sweetener
as a fermentative reagent

22. Refer: What is lactose intolerance?
lactose (milk sugar)
Refer: What is lactose intolerance?

23. Polysaccharides or glycans
Complex carbohydrates that are made up of hundreds of monosaccharides linked by glycosidic bonds.
Homoglycans
Heteroglycans
Starch
Cellulose
Glycogen
Inulin
Gums
Mucopolysaccharides

24. Polysaccharides
(Many sugar units)

25. Starch
Test for starch?
Answer

26. Identification of starch-Iodine test
Suspensions of amylose
in water adopt a helical
conformation.
Iodine (I2) can insert in
the middle of the amylose
helix to give a blue color
that is characteristic and
diagnostic for starch.
Back to question

27. Cellulose

28. Y X Control Test Following is the test results for 3 different sugars
Name the test
What is in X & Z?
What is in Y ?
Answer

29. Barfoed’s test X Y Answer
Following is the Barfoed’s test results for sugars. X Y
Tube Y contains ………..
Maltose
Glucose
Lactose
Answer

30. Seliwanoff’s test X Y Answer
Following is the Seliwanoff’s test results for sugars. X Y
Tube Y contains……….
Glucose
Maltose
Fructose
Answer

31. THE END
Back to the beginning

32. Q1- List the main function of carbohydrates
Sources of energy
Form structural components
cellulose, lignin, murein
Molecular recognition
Blood group antigens
Associated with other entities
DNA, RNA, glycosides, vitamins
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33. Q3:How to classify carbohydrates?
Number of monomers
Monosaccharides(1)
Disaccharides(2)
Oligosacchrides(2-10)
Polysaccharides or glycans(>10)
Homopolysaccharides
Heteropolysaccharides
Complex carbohydrates

34. Glucose measurement methods
Most are enzymatic methods
3 enzyme systems are currently used :
Glucose oxidase
Glucose dehydrogenase
Hexokinase

35. Glucose oxidase methods: colorimetric method

36. Back to the question

37. Can have two sets of answers
Benedict’s test
Reducing sugar
Non reducing sugar
Barfoed’s test
Disaccharides
Monosaccharides
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38. (Barfoed’s test is positive for Monosaccharides only)
Glucose
(Barfoed’s test is positive for Monosaccharides only)
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39. (Seliwanof’s test is positive for Keto sugars)
Fructose
(Seliwanof’s test is positive for Keto sugars)
Back to the question

40. 3 2 1 1 N0 2
Yes 3 N0 4 N0 5
Yes 4 5
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