3. Functions of Food to maintain life to supply energy & give warmth –carbohydrates –fats –proteins for growth and repair –Proteins keep healthy & help to fight against disease

4. elements : C, H, O –ratio of H : O = 2 : 1 monosaccharides –C 6 H 12 O 6 –all are sweet & soluble in water –all are Reducing Sugars –include Glucose, Fructose & Galactose Carbohydrates

5. u disaccharides (from 2 monosaccharides) – C 11 H 22 O 11 – all are sweet & soluble in water – Maltose ( 2 glucose molecules ) – Sucrose ( glucose + fructose) (non-reducing sugar) – Lactose ( glucose + galactose) Carbohydrates surcose surcose

6. Carbohydrates polysaccharides (NOT sugar) for energy storage –starch (store in plants) glycogen (store in animals) Hydrolysis: Polysaccharide + H 2 O  Disaccharides + H 2 O  Monosaccharides

7. u main source of energy u cellulose: - fibrous material of Plant Cell Wall - dietary fibre: stimulates Peristalsis u excess carbohydrates - stored as glycogen in liver & muscle - stored as fats under skin Functions of Carbohydrates

8. Test for Reducing Sugars (Benedict’s Test)

9. Is there any colour change in tubes A and B ? Ans: Only the mixture in tube A has a colour change. AB glucose solution + Benedict’s solution distilled water + Benedict’s solution water bath

10. What is the sequence of change when there is a colour change ? Ans: The blue solution changes first to green, then to a yellow coloration and eventually a brick-red precipitate is produced. AB glucose solution + Benedict’s solution distilled water + Benedict’s solution water bath

11. Test for Starch (Iodine Test)

12. What is the final colour in tube A ? Ans: The solution in tube A changes from brown to blue black. iodine solution starch solution distilled water A B

13. What is the purpose of setting up tube B ? Ans: To act as a control. iodine solution starch solution distilled water A B

14. Proteins elements: C, H, O, N, sometimes S, P components : amino acids forms dipeptides & polypeptides Condensation: Amino acids –H 2 O  Dipeptides –H 2 O  Polypeptide

15. u cannot be stored - excess proteins are deaminated by liver ~ to Urea which will be excreted away by Kidney ~ to Carbohydrates (Glycogen) which will be stored in Liver Proteins

16. Functions of Proteins for growth and repair (as structural components of cells) to produce hormones and enzymes to give energy for making Haemoglobin in blood for making Antibodies

17. Test for Proteins (Biuret Test)

18. What colour changes in tubes A and B ? Ans: Mixture in tube A changes from blue to purple while mixture in tube B remains blue without any change. copper sulphate solution egg white + sodium hydroxide solution water + sodium hydroxide solution A B

19. Lipids ( fats & oils ) elements : C, H, O components of 1 lipid molecule: 1 glycerol + 3 fatty acids insoluble in water soluble in organic solvent

20. Functions of Lipids u give energy u component of cell membrane u form fatty tissues under skin > to store energy > acts as insulator to keep warm u to transport fat-soluble vitamins (A, D, E, K)

21. Spot Test for Fat

22. Which substance, oil or water, leaves a permanent translucent spot on the filter paper ? Ans: Oil.

23. Emulsion Test for Fat

24. Which test tube has an emulsion formed ? Ans: Test tube A. 2 drops of cooking oil 2 cm 3 of alcohol 2 cm 3 of distilled water after shaking to form a clear solution shake and then allow to stand emulsion oil water shake and then allow to stand shaking 2 drops of cooking oil 2 cm 3 of distilled water A B

25. What happens to the other tube ? Ans: The mixture separates into two layers because fats do not dissolve in water. 2 drops of cooking oil 2 cm 3 of alcohol 2 cm 3 of distilled water after shaking to form a clear solution shake and then allow to stand emulsion oil water shake and then allow to stand shaking 2 drops of cooking oil 2 cm 3 of distilled water A B

26. Vitamins no energy value essential for small amount to maintain good health water soluble vitamins ( B, C ) fat soluble vitamins ( A, D, E, K ) u excessive of some vitamins may be harmful

27. Vitamin A  formed in the body from Carrotene (a yellow pigment in carrots)  destroyed at high temperature  essential for forming visual purple (maintain dim light vision)

28. Vitamin C  Destroyed after prolonged cooking  Necessary for wounds-healing Vitamin D  Formed in Skin from Ultraviolet Light  Help to regulate Ca & P metabolism

29. Detection of Vitamin C in Lemon Juice by using DCPIP

30. What colour change has occurred ? Ans: The blue DCPIP decolourizes. syringe lemon juice DCPIP solution

31. What conclusion can you draw ? Ans: Lemon juice contains vitamin C which decolourizes blue DCPIP. syringe lemon juice DCPIP solution

32. VitaminSources Deficiency Disease A Egg yolk, milk, cheese, carrot, green vegetables Night blindness C Fresh fruits & green vegetables Scurvy D Cod liver oil & egg yolk Rickets

33. Food Tests SubstancesTest Original Colour Positive Result Reducing Sugar Benedict’sBlueOrange ppt StarchIodineBrownBlue-black ProteinBiuretBlue Violet Fats/OilsSpot --- Translucent spot Fats/OilsEmulsionClearMilky emulsion Vitamin CDCPIPBlue Colourless (decolourize)

34. Mineral Salts u regulate body metabolism u essential for healthy growth u necessary for construction of certain tissues u needed in small amount u include Ca, S, K, Na, Mg, Fe, I

35. Mineral(s) SourcesFunctions Deficiency Disease Calcium & Phosphorus Cheese, milk, vegetables Making bones & teeth Important for blood clotting & muscle contraction Rickets Iron Liver, eggs, beef, green leafy vegetables Structural component of Haemoglobin Anaemia

36. Dietary Fibre u mainly cellulose u indigestible material for human u give bulk to food & stimulate peristalsis  prevent Constipation u lack of dietary fibre: Large Intestine Cancer u sources: wholemeal cereals, unpolished rice, fresh vegetables & fruits

37. Balanced Diet have enough food to supply enough –energy carbohydrates, fats, proteins –body building materials proteins –substances to maintain health vitamins, minerals, water & dietary fibres malnutrition : not having balanced diets for long time

38. Energy Contents in Food Calorimeter is used to measure the amount of energy contained in a particular type of food Carbohydrate (17kJ/g) Protein (18kJ/g) Fat (39kJ/g)

39. Factors affecting energy requirement Sex Age Occupation Physical Activities Stage of individual (pregnancy, breast-feeding)

40. Measure the Energy Value of Food

41. boiling tube water burning peanut thermometer Explain why the energy value of the peanut is lower than those from standard tables. Ans: Because there are a number of inaccuracies associated with this method due to incomplete combustion and heat loss.

42. Basal Metabolic Rate (BMR) u minimum amount of energy needed by an individual lying awake in bed to maintain breathing, body temperature & heartbeat u varies from one individual to another u daily energy requirement > basal metabolic rate

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