1.2 CARBOHYDRATES

1. 1.2 CARBOHYDRATES 1.1 WATER 1.3 LIPIDS MOLECULES OF LIFE 1.5 NUCLEIC ACIDS 1.4 PROTEINS

2. 1.2 CARBOHYDRATES

3. 1.2 Carbohydrates (1 1/2 hour) Objectives : • Describe various forms and classes of carbohydrates such as monosaccharides, disaccharides & polysaccharides. • Describe the formation and breakdown of maltose. • Describe the structures and functions of starch, glycogen & cellulose.

5. 3 main classes

6. CARBOHYDRATES • allare composed ofcarbon(C), hydrogen (H) & oxygen(O) atoms; • usually in the proportion1:2:1 respectively

7. CARBOHYDRATES MONOSACCHARIDES • characteristics: • simple sugars: - cannot be broken down into smaller molecules byhydrolysis • sweet-tasting • soluble in water

8. MONOSACCHARIDES • ..characteristics: • can be crystallized • reducing agents: - it has an open chain with an aldehyde or a ketone group. 6. can be the monomers for disaccharides&polysaccharides

9. MONOSACCHARIDES • general formula: ( CH2O )n n = number of C atoms in the molecule, ( n = 3, 4, 5, 6, 7 ) eg: glucose ~ C6H12O6 ~ most names for sugars end with -ose

10. CARBOHYDRATES

11. MONOSACCHARIDES • STRUCTURE • straight-chain form, ring form in aqueous • a sugar has; • i. acarbonyl group( C = O ) • ii. manyhydroxyl groups( -OH )

12. can be classified as; 1. based on the typeoffunctional group( aldehydeorketone ) 2. by the number of carbon atomsin the backbone

13. CLASSIFICATION : FUNCTIONAL GROUP • if the carbonyl group ( C=O ); at one end of the molecule ( C1 atom ) aldehyde group = the sugar is an aldose • if in the middleof the molecule ( C2 atom ) ketone group • = the sugar isketose

14. Aldehyde Ketone

15. CLASSIFICATION : NUMBER OF CARBONS also classified by the number of carbon atomsin the backbone; Triose sugar ( 3C sugars ): ~ contains 3 carbon atoms ~ C3H6O3 ~ eg: glyceraldehyde Pentose sugar ( 5C sugars ): ~ contains 5 carbon atoms ~ C5H10O5 ~ eg: ribose, deoxyribose Hexose sugar ( 6C sugars ): ~ contains 6 carbon atoms ~ C6H12O6 ~ eg: glucose, galactose & fructose

16. CLASSIFICATION : FUNCTIONAL GROUP & NUMBER OF CARBONS

18. Triose sugar: Glyceraldehyde

19. Pentose sugar

20. Hexose sugar : Glucose

21. Structure of Glucose Aldohexose

22. Two ring structure of glucose •  - glucose and - glucose • difference : whether the hydroxyl group(-OH) attached to the number 1 carbon is fixed • above ( - glucose) or • below ( - glucose)

23. Ring structure Linear structure

24. ..Two ring structure of glucose • both areisomers (different compoundswith thesame molecular formula C6H12O6)

25. 1 1 Hexose sugar : Glucose

27. CARBOHYDRATES DISACCHARIDES • sweet&water soluble • a double sugarmolecule (consists of2 monosaccharides) • Can be crystallized

28. CARBOHYDRATES Glycosidicbondofcarbohydrates; • bondbetween 2monosaccharides; • formationby acondensation reaction; • removal of water molecule • breakageby ahydrolysis reaction; • addition of water molecule

29. CARBOHYDRATES DISACCHARIDES Maltose( malt sugar ) =α-glucose + α-glucose ~ as respiratory substrate ~ reducing sugar Sucrose( cane sugar ) = α-glucose + fructose ~ main form that is transported in plant ~ non-reducing sugar Lactose( milk sugar ) =β-glucose + galactose ~ source for energy ~ reducing sugar

30. CARBOHYDRATES Reducing agent: depend on freefunctional group ( aldehyde & ketone ) at sugar structure Sucrose: ~ non-reducing sugar Maltose & Lactose ~ reducing sugar

31. MALTOSE = α-glucose + α-glucose condensation hydrolysis α-1,4 This reducing group is still free

32. SUCROSE =α-glucose + fructose condensation hydrolysis α-1,2 A non-reducing sugar because the aldehyde group of glucose is linked to the ketone group of fructose

33. 6 6 O O 5 5 4 4 1 1 3 3 2 2 Disaccharides: LACTOSE CH2OH CH2OH O H OH HO H H H OH OH H H H OH H H H OH H OH + galactose β- glucose

34. 6 6 O O 5 5 4 4 1 1 3 3 2 2 Disaccharides: LACTOSE CH2OH CH2OH OH HO H H H O OH OH H H H H H H OH H OH H2O Lactose ( β-1,4 glycosidicbond )

35.  LACTOSE = galactose + glucose Raven pg 54, fig 3.23

37. CARBOHYDRATES POLYSACCHARIDES POLYSACCHARIDES • complex macromolecules • polymersformed when many hundreds ofmonosaccharidesjoined byglycosidic bonds( throughcondensation) • breakdownbyhydrolysis

38. POLYSACCHARIDES • The chains formed may be: • variable in length • branched or unbranched • folded – ideal for energy storage • straight or coiled

39. POLYSACCHARIDES • characteristic of polysaccharides: • large • not sweet • insoluble in water • Cannot be crystallized

40. POLYSACCHARIDES examples: • STARCH (plant food storage) • GLYCOGEN (animal food storage) • CELLULOSE (components of plant cell wall)

41. POLYSACCHARIDES Starch • used for energy storage in plants • a polymer consists of α-glucose subunits • occurs in 2 forms: • Amylose • Amylopectin

42. Starch : storedas granuleswithin plastids in leaves, potato tubers, cereals & rice

43. CARBOHYDRATES Starch Amylose: • subunit: α-glucose • unbranchedhelical chains, • only one type of linkage: • α-1,4 glycosidicbond

44. Amylose Hydrogen bond Monomers linked by α-1,4 glycosidic bond

45. ..Amylose • amylose chain coils intohelix held byhydrogen bondsformedbetweenhydroxyl ( -OH ) groups ~ a more compactshape is formed

46. Hydrogen bond

47. CARBOHYDRATES Starch Amylopectin: • subunit: α-glucose • branched chains every 30 units, • have 2 types of linkages: • α-1,4 glycosidic bond & • α-1,6 glycosidicbond

48. α- 1,6 glycosidic bond Amylopectin α-1,4 glycosidicbonds

49. CARBOHYDRATES Glycogen • carbohydrate energy stored in animals • found in liver &muscle tissue • structure is similar to that ofamylopectin butmore extensively branched

50. Glycogen