2. 1 BIOLOGY PRESENTATIONS FOR A-LEVEL, IN MULTIMEDIA JAMES BOWLES, 2001 BIOLOGY PRESENTATIONS FOR A-LEVEL, IN MULTIMEDIA JAMES BOWLES, 2001 LEFT CLICK OR PRESS SPACE BAR TO ADVANCE, PRESS P BUTTON TO GO BACK, PRESS ESC BUTTON TO END LEFT CLICK OR PRESS SPACE BAR TO ADVANCE, PRESS P BUTTON TO GO BACK, PRESS ESC BUTTON TO END

3. 2 ‘A’ Level Biology Carbohydrates

4. 3 Carbon Nucleus contains 6 protons and 6 neutrons.

5. 4 Surrounded by 6 electrons (4 in outer shell) It is, therefore capable of forming 4 stable covalent bonds (Tetravalent) Carbon

6. 5 Nucleus contains 6 protons and 6 neutrons. It is, therefore capable of forming 4 stable covalent bonds (Tetravalent) It is able to form covalent bonds with other carbon atoms, allowing it to form the backbone of biomolecules Carbon Surrounded by 6 electrons (4 in outer shell)

7. 6 Nucleus contains 6 protons and 6 neutrons. It is, therefore capable of forming 4 stable covalent bonds (Tetravalent) It is able to form covalent bonds with other carbon atoms, allowing it to form the backbone of biomolecules Carbon Surrounded by 6 electrons (4 in outer shell)

8. 7 Carbohydrates Most abundant (by mass) biomolecule in nature

9. 8 Most abundant (by mass) biomolecule in nature Contain: Carbon Oxygen Hydrogen Simplest formula is (CH 2 O)n

10. 9 Glucose 6 Carbons 6 Oxygens 12 Hydrogens C 6 H 12 O 6

11. 10 1 2 3 4 5 6 (C 6 H 12 O 6 ) For convenience carbons are numbered, starting with the one with the aldehyde group Glucose

12. 11 (C 6 H 12 O 6 ) Glucose This is optical isomerism 222 Carbons are asymmetric since OH and H and can be on either side 22222

13. 12 Ring Formation Aldehyde group on carbon 1 bonds with hydroxyl group on carbon 5 (C 6 H 12 O 6 ) 1 2 3 4 5 6 Glucose

14. 13 1 2 3 4 5 6

15. 14 Carbon 1 is now asymmetrical 1 2 3 4 5 6

16. 15  Glucose 1 2 3 4 5 6 There are two forms of glucose in ring structure

17. 16  Glucose 1 2 3 4 5 6 There are two forms of glucose in ring structure

18. 17 6 3 2 4 1 5

19. 18 CH 2 OH 3 2 4 1 5 For simplicity not all the components are shown

20. 19 Glycosidic Bond CH 2 OH 3 2 4 1 5 3 2 4 1 5 Monosaccharides join via an oxygen bridge between carbon 1 and carbon 4 of adjacent sugars

21. 20 Glycosidic Bond CH 2 OH 3 2 4 1 5 3 2 4 1 5 The bond involves the two hydroxyl groups

22. 21 CH 2 OH 3 2 4 1 5 3 2 4 1 5 Glycosidic Bond Water is produced - this is a CONDENSATION reaction

23. 22 CH 2 OH 3 2 4 1 5 3 2 4 1 5 Glycosidic Bond The reverse of this is HYDROLYSIS

24. 23 CH 2 OH 3 2 4 1 5 3 2 4 1 5 The reverse of this is HYDROLYSIS Glycosidic Bond

25. 24 Disaccharides 1 4 CH 2 OH 3 2 4 5 3 2 1 5 1 4 Maltose Found in germinating seeds and the alimentary canal – breakdown of starch  Glucose  1-4 Glycosidic bond

26. 25 Disaccharides Sucrose Found in sugar beet and sugar cane  Glucose Fructose  1-2 Glycosidic bond 1 CH 2 OH 3 2 4 5 1 5 43 2 5

27. 26 Disaccharides 1 4 CH 2 OH 3 2 4 5 3 2 1 5 1 4 Lactose Found in Milk  Galactose  Glucose  1-4 Glycosidic bond

28. 27 Testing for Reducing Sugars

29. 281. Combine equal quantities of test solution and Benedict’s reagent in a test tube Testing for Reducing Sugars

30. 292. Warm in a water bath Testing for Reducing Sugars

31. 30 Testing for Reducing Sugars 3. Change in colour and opacity indicate the reducing sugar concentration

32. 31 Testing for Non-Reducing Sugars CH 2 OH 3 2 4 1 5 3 2 4 1 5 1. Hydrolyse the glycosidic bond with warm dilute HCl

33. 32 2. Neutralise with NaHCO 3 Testing for Non-Reducing Sugars 3. Perform a Benedict’s test

34. 33 Polysaccharides - Starch CH 2 OH 2 components to starch : Amylose and Amylopectin Amylose is an unbranched molecule of glucose units bound by 1 – 4 glycosidic bonds

35. 34 Polysaccharides - Starch The chain of glucose molecules arranges itself as a helix

36. 35 Polysaccharides - Starch The chain of glucose molecules arranges itself as a helix The bore of which is the same size as a molecule of iodine in KI

37. 36 Polysaccharides - Starch Amylopectin is a branched molecule with 1-4 glycosidic bonds, And occasional 1-6 bonds forming branches

38. 37 Polysaccharides - Starch Branches arise every 25 th 25 th or so glucose molecule

39. 38 Polysaccharides - Glycogen 30 000 glucose units joined by 1-4 and 1-6 glycosidic bonds Similar structure to amylopectin, but with more frequent branching

40. 39 1 2 3 4 5 6  glucose Polysaccharides - Cellulose

41. 40 1 2 3 4 5 6 Polysaccharides - Cellulose Straight chain molecule of 1-4 glycosidic bonds, stabilised by hydrogen bonds between adjacent glucoses

42. 41Hydrogen bonds also exist between adjacent chains – molecule of high tensile strength 1 2 3 4 5 6 Polysaccharides - Cellulose

43. 42