biobook

1. بسم الله الرحمن الرحيم BIOCHEMISTRY

2. Course outline • Chapter one: carbohydrates • Chapter two: lipids structure and function • Chapter three: proteins • Chapter four: enzymes catalytic reaction. • Chapter five: vitamins

3. Course objectives Upon completion of this course students will demonstrate the basic knowledge of the following • Structures, names, and biological importance of a variety of carbohydrates • Structures, names, and biological importance of a variety of lipids • Structures and functions of amino acids and proteins • Functions of enzymes • Metabolism and energy production

4. Outline of instructions • Carbohydrates • Types of Carbohydrates • Classification, structures and sources of some important monosaccharaides • Disaccharides • Polysaccharides

5. Lipids • Fatty acids • Waxes, fats and oils. • Chemical properties of triglycerides • Solubility and polarity • Phospholipids, steroids and other lipids • Cell membrane

6. Amino acids (proteins) • Amino acids and protein structures • Functions of proteins • Levels of protein structure • Enzymes

7. Chapter one Carbohydrates

8. Carbohydrates are • A major source of energy from our diet. • Composed of the elements C, H, and O. • Also called saccharides, which means “sugars.”

9. Carbohydrates • Are produced by photosynthesis in plants. • Such as glucose are synthesized in plants from CO2, H2O, and energy from the sun. • Are oxidized in living cells (respiration) to produce CO2, H2O, and energy.

10. Types of Carbohydrates The types of carbohydrates are • Monosaccharides, the simplest carbohydrates. • Disaccharides, which consist of two monosaccharides. • Polysaccharides, which contain many monosaccharides.

11. Monosaccharides Monosaccharides consist of • 3 to 6 carbon atoms, typically. • A carbonyl group (aldehyde or ketone). • Several hydroxyl groups.

12. Aldoses O ║ C─Haldose │ H─ C─OH │ H─ C─OH │ CH2OH Erythose, an aldotetrose Aldoses are monosaccharides • With an aldehyde group. • With many hydroxyl (─OH) groups. triose (3 C atoms) tetrose (4 C atoms) pentose (5 C atoms) hexose (6 C atoms)

13. Ketoses CH2OH │ C=O ketose │ H─ C─OH │ H─ C─OH │ H─C─OH │ CH2OH Fructose, a ketohexose Ketoses are monosaccharides • With a ketone group. • With many hydroxyl (─OH) groups. triose (3 C atoms) tetrose (4 C atoms) pentose (5 C atoms) hexose (6 C atoms)

14. Learning Check Identify each as aldo- or keto- and as tetrose, pentose, or hexose: A B

15. Solution A. aldohexose B.ketopentose

16. Structures of Monosaccharides

17. Fischer Projections A Fischer projection • Is used to represent carbohydrates. • Places the most oxidized group at the top. • Shows chiral carbons as the intersection of vertical and horizontal lines.

18. D and L Notations In a Fischer projection, the −OH group on the • Chiral carbon farthest from the carbonyl group determines an L or D isomer. • Left is assigned the letter Lfor the L-isomer. • Right is assigned the letter Dfor the D-isomer.

19. Examples of D and L Isomers of Monosaccharides D-glucose D-ribose L-galactose

20. Learning Check Identify each as the D or L isomer. A. B. C. __-ribose __- threose __- fructose

21. Solution Identify each as the D or L isomer. A. B. C. L-ribose L-threose D-fructose

22. D-Glucose D-glucose is • Found in fruits, corn syrup, and honey. • An aldohexose with the formula C6H12O6. • Known as blood sugar in the body. • The monosaccharide in polymers of starch, cellulose, and glycogen.

23. Blood Glucose Level In the body, • Glucose has a normal blood level of 70-90 mg/dL. • A glucose tolerance test measures blood glucose for several hours after ingesting glucose.

24. D-Fructose D-fructose • Is a ketohexose C6H12O6. • Is the sweetest carbohydrate. • Is found in fruit juices and honey. • Converts to glucose in the body.

25. D-Galactose D-galactose is • An aldohexose C6H12O6. • Not found free in nature. • Obtained from lactose, a disaccharide. • A similar structure to glucose except for the –OH on C4.

26. Learning Check Draw the structure and Fischer projection of D-fructose.

27. Solution CH2OH │ C=O HO H H OH H OH CH2OH Fischer projection

28. Cyclic Structures of Monosaccharides Copyright © 2007 by Pearson Education, Inc Publishing as Benjamin Cummings

29. Cyclic structures • Are the prevalent form of monosaccharides with 5 or 6 carbon atoms. • Form when the hydroxyl group on C-5 reacts with the aldehyde group or ketone group.

30. Cyclic Haworth Structures Stable cyclic hemiacetals form • When the C=O group and the —OH are part of the same molecule. • For hexoses, the hydroxyl group on C-5 reacts with the aldehyde group or ketone group. • The cyclic structure of a D-isomer has the last CH2OH group located above the ring.

31. Drawing the Cyclic Structure for Glucose STEP 1 Number the carbon chain and turn clockwise to form a linear open chain. 1 2 3 4 5 6 6 5 4 3 2 1

32. STEP 2 Bend the chain to make a hexagon • Bond the C5 –O– to C1. • Place the C6 group above the ring. • Write the –OH groups on C2 and C4 below the ring. • Write the –OH group on C3 above the ring. • Write a new –OH on C1. 6 5 4 1 3 2

33. STEP 3 The new –OH on C1 is drawn • Down for the  anomer. • Up for the  anomer.   -D-glucose-D-glucose

34. Summary of the Formation of Cyclic Glucose Copyright © 2007 by Pearson Education, Inc Publishing as Benjamin Cummings

35. -D-Glucose and β-D-Glucose in Solution When placed in solution, • Cyclic structures open and close. • -D-glucose converts to β-D-glucose and back. • There is only a small amount of open chain. -D-glucose D-glucose (open) β-D-glucose (36%) (trace) (64%)

36. Cyclic Structure of Fructose Fructose • Is a ketohexose. • Forms a cyclic structure. • Reacts the —OH on C-5 with the C=O on C-2. α-D-fructose D-fructose -D-fructose

37. Learning Check Write the cyclic form of -D-galactose

38. Solution -D-galactose

39. Carbohydrates Chemical Properties of Monosaccharides

40. Reducing Sugars Reducing sugars • Are monosaccharides with a carbonyl group that oxidizes to give a carboxylic acid. • Undergo reaction with Benedict’s reagent (Cu2+) to give the corresponding carboxylic acid. • Include the monosaccharides glucose, galactose, and fructose.

41. Oxidation of D-Glucose Glucose is oxidized to a carboxylic acid Benedicts reagent [O] Cu+ (reduced form) Glucose is a reducing sugar

42. Reduction of Monosaccharides D-Glucitol The reduction of monosaccharides • Involves the carbonyl group. • Produces sugar alcohols called alditols. • Such as D-glucose gives D-glucitol also called sorbitol.

43. Learning Check Write the products of the oxidation and reduction of D-mannose. D-mannose

44. Solution Write the products of the oxidation and reduction of D-mannose. D-mannitol D-mannose D-mannonic acid

45. Disaccharides

46. Important Disaccharides A disaccharide • Consists of two monosaccharides. Monosaccharides Disaccharide Glucose + glucose maltose + H2O Glucose + galactose lactose + H2O Glucose + fructose sucrose + H2O

47. Maltose Maltose is • A disaccharide also known as malt sugar. • Composed of two D-glucose molecules. • Obtained from the hydrolysis of starch. • Linked by an -1,4-glycosidic bond formed from the  −OH on C1 of the first glucose and −OH on C4 of the second glucose. • Used in cereals, candies, and brewing. • Found in both the - and β - forms.

48. Formation of Maltose

49. Lactose Lactose • Is a disaccharide of β-D-galactose and α- orβ-D-glucose. • Contains a β -1,4-glycosidic bond. • Is found in milk and milk products. α-form

50. Sucrose Sucrose or table sugar • Is obtained from sugar cane and sugar beets. • Consists of α-D-glucose and β-D-fructose.. • Has an α,β-1,2-glycosidic bond. α-D-glucose β-D-fructose