Classification of Carbohydrate Part-I.pptx

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1.   Carbohydrate Mr. Abhijit Bhoyar Assistant Professor Department of Child Health Nursing CLASSIFICATION Part-I

2. Specific Learning Objectives At the end of the lecture, the students will be able to Classify carbohydrate.

3. Introduction Carbohydrates are often referred to as saccharides (Greek: sakcharon–sugar). This categorization is based on the number of sugar units. Mono- and oligosaccharides are sweet to taste, crystalline in character and soluble in water, hence they are commonly known as sugars . They are broadly classified into three major groups .

4. Monosaccharides The word “Monosaccharides” derived from the Greek word “Mono” means Single and “saccharide” means sugar. Monosaccharides are the simplest group of carbohydrates and are often referred to as simple sugars. Monosaccharides are polyhydroxy aldehydes or ketones which cannot be further hydrolysed to simple sugar .

5. Cont…. They have the general formula Cn(H2O)n. They are sweet in taste , soluble in water and crystalline in nature. They contain 3 to 10 carbon atoms, 2 or more hydroxyl (OH) groups and one aldehyde (CHO) or one ketone (CO) group. The monosaccharides are divided into different categories, based on the functional group and the number of carbon atoms

6. Properties of Monosaccharides Colour - colorless Shape - crystalline Solubility – water soluble Taste - sweet Optical activity – Optically active. Dextrorotatory (‘d’ form) and ( b) Levorotatory (‘l’ form ).

7. Dextrorotatory (‘d’ form) and (b) Levorotatory (‘l’ form). If a compound rotates plane polarized light in the clockwise (+) direction, it is said to be dextrorotatory, while if it rotates light in the counterclockwise (-) direction it is levorotatory. 

8. Cont.…. Mutarotation – ( a gradual change in the optical rotation of freshly prepared solutions of reducing sugars)

9. Cont…. Glucoside formation - Glucose + Methyl alcohol = Methyl glucoside Esterification- It is a chemical reaction that takes place during the formation of the ester. Esterification is the chemical process that combines alcohol (ROH) and an organic acid (RCOOH) to form an ester (RCOOR) and water .

10. Cont…. Reducing agents – (a substance that reduces a chemical compound usually by donating electrons .) Monosaccharides reduce oxidizing agent such as hydrogen peroxide . In such reaction, sugar is oxidized at the carbonyl group and oxidizing agent becomes reduced . Formation of Osazone- A yellow crystalline compound formed by the action of phenyl-hydrazine on a sugar in the presence of acetic acid .

11. Classification of Monosaccharides Monosaccharides are classified in two ways Based on the number of carbon atoms present in them Based on the presence of carbonyl group.

12. Based on the number of carbon atoms present in them The naturally occurring monosaccharides contain three to seven carbon atoms per molecule. Monosaccharides of specific sizes may be indicated by names composed of a stem denoting the number of carbon atoms and the suffix - ose . For example , the terms triose, tetrose , pentose, and hexose signify monosaccharides with, respectively, three, four, five, and six carbon atoms.

13. Cont…. Based on the number of carbon atoms, the monosaccharides are regarded as Trioses (3C) Tetroses (4C) Pentoses (5C) Hexoses (6C) Heptoses (7C)

14. Based on the presence of carbonyl group Monosaccharides are also classified as

15. Cont…. Aldoses : Those monosaccharides that contain an aldehyde functional group are called aldoses. e.g. Glyceraldehyde, Glucose. Ketoses : Those monosaccharides containing a ketone functional group on the second carbon atom are referred to as ketoses. e.g. Dihydroxyacetone, Fructose.

16. Cont…. Combining these classification systems gives general names that indicate both the type of carbonyl group and the number of carbon atoms in a molecule. Thus , monosaccharides are described as aldotetroses , aldopentoses , ketopentoses , ketoheptoses . Glucose and fructose are specific examples of an aldohexose and a ketohexose, respectively .

17. Classification of monosaccharides with selected examples Monosaccharides (empirical formula) Aldose Ketose Trioses (C3H6O3) Glyceraldehyde Dihydroxyacetone Tetroses (C4H8O4) Erythrose Erythrulose Pentoses (C5H10O5) Ribose Ribulose Hexoses (C6H12O6) Glucose Fructose Heptoses (C7H14O7) Glucoheptose Sedoheptulose

18. Trioses Trioses are “Monosaccharides” containing 3 carbon atoms. The molecular formula of triose is C3H6O3. Characteristics Trioses are simple sugars and soluble in water. They are sweet in taste. The triose may contain an aldehyde group ( aldotriose ) or a ketone group. ( ketotriose ). Example- Glycerose and Dehydroxyacetone

19. Tetroses Tetroses are “Monosaccharides” containing 4 carbon atoms. The molecular formula of tetrose is C4H8O4. Characteristics Tetroses are simple sugars and soluble in water. They are sweet in taste and crystalline forms. The tetroses may contain an aldehyde group ( (ketotetrose).

20. Pentoses Pentoses are “Monosaccharides” containing 5 carbon atoms. It is an important component of “nucleic acid”. The molecular formula of Pentose is C5H10O5

21. Characteristics of Pentoses Pentoses are simple sugars. Pentoses are soluble in water . They are sweet in taste. They are crystalline forms. The pentoses may contain an aldehyde group ( aldopentose ) or a ketone group ( ketopentose ).

22. Hexoses Hexoses are “Monosaccharides” containing 6 carbon atoms. The molecular formula of Hexose is C6H12O6. Characteristics Hexoses are simple sugars and soluble in water. They are sweet in taste. They are crystalline forms. The pentoses may contain an aldehyde group ( aldohexose (ketohexose)

23. Oligosaccharides Oligosaccharides (Greek: oligo-few) contain 2-10 monosaccharide molecules which are liberated on hydrolysis. Based on the number of monosaccharide units present , the oligosaccharides are further subdivided to disaccharides, trisaccharides etc.

24. Types of Oligosaccharides Disaccharides Trisaccharides Tetrasaccharides

25. Disaccharides Disaccharides are the most common among the oligosaccharides . D isaccharide consists of two monosaccharide units (similar or dissimilar) held together by a glycosidic bond.

26. Cont… They are crystalline, water-soluble and sweet to taste . The most abundant disaccharides are sucrose , lactose and maltose. Other disaccharides include isomaltose, cellobiose and trehalose

27. Types Of Disaccharides The disaccharides are of two types Reducing disaccharides with free aldehyde or keto group e.g. maltose, lactose. Non-reducing disaccharides with no free aldehyde or keto group e.g. sucrose, trehalose .

28. Maltose Maltose which is also known as malt is a disaccharide made up of two alpha D glucose unit. The two-unit of glucose are linked with an alpha 1,4 glycosidic bond.  In the small intestinal lining in humans, the enzyme maltase and isomaltase break down the molecules of maltose into two glucose molecule , which is then absorbed by the body . Maltose = 2 molecules of glucose

29. Sucrose Sucrose (cane sugar) is the sugar, mostly produced by sugar cane and sugar beets. Sucrose is made up of α -D-glucose and β - D-fructose . The two monosaccharides are held together by a glycosidic bond (D1 o E2), between C1 of D-glucose and C2 of E-fructose. The reducing groups of glucose and fructose are involved in glycosidic bond , hence sucrose is a non-reducing sugar , and it cannot form osazones.

30. Cont…. Sucrose is an important source of dietary carbohydrate . It is sweeter than most other common sugars (except fructose) namely glucose, lactose and maltose . Sucrose is employed as a sweetening agent in food industry. The intestinal enzyme— sucrase —hydrolyses sucrose to glucose and fructose which are absorbed . 1 mol. of glucose + 1 mol. Of fructose

31. Lactose Lactose is more commonly known as milk sugar since it is the disaccharide found in milk . Lactose is composed of β - D-galactose and β –D glucose held together by β (1 4 ) glycosidic bond. 1 mol. Of glucose + 1 mol. Of galactose

32. Trisaccharides It composed of three monosaccharide . E x : Raffinose (Formed by one mole of each i.e. glucose, fructose, galactose). It is presnt in molasses

33. Tetrasaccharides It Composed of four monosaccharide . E x : Stachyose- (composed of two moles of galactose one mole of glucose & one mole of fructose ). It is present in onion.

34. Summary So far we have discussed about classification of carbohydrate.

35. Expected Questions Essay/Situational Type Define carbohydrate and classify it in detail.

36. References Jacob Anthikad, Biochemistry for nurses 3 rd ed. Pankaja Naik, Essentials of Biochemistry, 1 st ed. Satyanarayan, Essentials of Biochemistry, 2 nd ed. A. C. Deb, Biochemistry, 4 th ed.

37. THANK YOU