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Food and diet

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Food and diet

  1. 1. Food is needed for: 1. 2. 3. 4. Energy and warmth Growth Repairing and replacing tissues Keeping the body healthy and fight disease
  2. 2. The amount of energy needed by a person depends upon:1) 2) 3) 4) age sex temperature job
  3. 3. A balanced diet is composed of the right amounts of:1. 2. 3. 4. 5. 6. 7. Water Carbohydrates Lipids Proteins Mineral salts Vitamins Dietary fibre or roughage
  4. 4. The food guide pyramid 1. 2. 3. 4. 5. 6. 7. Water Carbohydrates Lipids Proteins Mineral salts Vitamins Dietary fibre or roughage
  5. 5. Malnutrition  condition that results from taking an unbalanced diet in which certain nutrients are:  lacking  in excess (too high an intake)  or in the wrong proportions
  6. 6. Components of a balanced diet :1. 2. 3. 4. 5. 6. 7. Water Carbohydrates Lipids Proteins Mineral salts Vitamins Dietary fibre or roughage
  7. 7. Uses of water in organisms:1. as part of cytoplasm (most cells contain 75% water) 2. as a solvent in which chemical reaction occur 3. to activate enzymes 4. for photosynthesis in plants 5. for growth and support in plants 6. to transport substances round the body (blood has a lot of water) 7. brings about cooling on evaporating
  8. 8. Animals get water from:1. Drinking 2. Eating 3. Chemical reactions e.g. respiration food H2O O2 ATP
  9. 9. Components of a balanced diet :1. 2. 3. 4. 5. 6. 7. Water Carbohydrates Lipids Proteins Mineral salts Vitamins Dietary fibre or roughage
  10. 10. CARBOHYDRATES  contain the elements:  Carbon  Hydrogen  Oxygen  have more oxygen than fats  Glucose:  is the simplest carbohydrate (C6 H12 O6)
  11. 11. Easy to remember elements: Food Carbohydrates Lipids Proteins Elements C, H, O C, H, O C, H, O, N [sometimes S and P]
  12. 12. Food rich in carbohydrates
  13. 13. Uses of carbohydrates:a) provide energy (17kJ/g) Sugar in energy drink equivalent to six pastries.
  14. 14. Question: MAY, 2004 Give biological explanations for each of the following statements: The diet of athletes is usually high in carbohydrates. (5) Athletes need a lot of energy. Carbohydrates are the body’s main energy source. Carbohydrates like starch in bread are digested into glucose. Glucose is used in respiration to release energy. If athletes take in monosaccharides, i.e. sugars e.g. glucose, they are provided with energy very quickly.
  15. 15. Uses of carbohydrates:b) to store energy e.g. starch in potatoes or roots c) to build cell walls in plants Cell wall Storage organs
  16. 16. Uses of carbohydrates:d) fibre is important to prevent constipation Food sources of fibre: whole wheat, bran, fresh or dried fruit & vegetables. Constipated!!
  17. 17. In what form are excess carbohydrates stored? 1) in plants: starch 2) in animals: glycogen Name two places in animals where glycogen is stored. Liver & muscles
  18. 18. Three types of carbohydrates 1. Monosaccharides e.g. glucose, fructose 2. Disaccharides e.g. maltose, lactose, sucrose 3. Polysaccharides e.g. starch, glycogen, cellulose
  19. 19. Monosaccharides Disaccharides Polysaccharides Sweet & Soluble Not sweet & Insoluble
  20. 20. Name the monosaccharide which forms starch, glycogen and cellulose. Glucose Glycogen Cellulose Starch
  21. 21. How do starch, glycogen and cellulose differ? The way glucose units are linked together Glycogen Cellulose Starch
  22. 22. Question: MAY, 2008 (IIB) Where in a plant would you expect to find: i) Cellulose (1) ii) Starch (1) i) Cellulose – found in cell walls of plant cell ii) Starch – found stored in roots / storage organs
  23. 23. Why is the tired athlete choosing sugar rather than starch? Sugars, especially monosaccharides can be used for respiration right away. Starch needs to be digested first.
  24. 24. Components of a balanced diet :1. 2. 3. 4. 5. 6. 7. Water Carbohydrates Lipids Proteins Mineral salts Vitamins Dietary fibre or roughage
  25. 25. LIPIDS  a name for fats and oils  contain the elements:- C, H, O lard
  26. 26. Food rich in lipids:Nuts Egg yolk
  27. 27.  uses of lipid a) provide energy (39 kJ/g) b) store energy
  28. 28.  uses of lipid c) insulation in mammals d) protection of delicate organs from bumps Fat lines body wall of a rabbit. Fat around kidney.
  29. 29. Question: MAY, 2008 (IIB) Explain why one kilogram of starch crops releases less energy when burnt, compared to one kilogram of oil crops. (2) Starch is a carbohydrate whilst oil is a lipid. Carbohydrates have a lower energy content than lipids.
  30. 30.  building blocks of a lipid molecule:  Glycerol  Fatty acids A molecule of fat
  31. 31.  excess lipids are stored:1) in the ADIPOSE TISSUE under the skin 2) around organs Fat around heart.
  32. 32. What does this pyramid show about intake of lipids? Few lipids must be taken.
  33. 33. What happens to a person’s weight when: Weight remains constant
  34. 34. What happens to a person’s weight when: Obese person Weight increases
  35. 35. What happens to a person’s weight when: Weight decreases
  36. 36. Components of a balanced diet :1. 2. 3. 4. 5. 6. 7. Water Carbohydrates Lipids Proteins Mineral salts Vitamins Dietary fibre or roughage
  37. 37. PROTEINS  contain the elements: C, H, O, N (sometimes S and P)  food rich in proteins: Meat  Fish  Egg white  Cheese
  38. 38.  Uses of proteins:1. for growth 2. for cell repair and replacement 3. to make enzymes 4. to make antibodies
  39. 39. What are the building blocks of proteins called?
  40. 40.  Two amino acids are linked by a: Peptide bond  Polypeptide: many amino acids are linked
  41. 41.  A protein: many polypeptides joined up
  42. 42. different amino acids occur in proteins
  43. 43.  Two types of amino acids: 1. Essential [8 amino acids] must be eaten as they cannot be made by the body 2. non-essential can be made by the body
  44. 44.  contain significant amounts of all the essential amino acids  Source: animals : eggs, meat, fish, cheese  deficient in one or more essential amino acid  Source: plants
  45. 45.  For example, corn is deficient in one amino acid  Individuals who eat only corn would show symptoms of protein deficiency. • This is true from any diet limited to a single plant source, including:  Rice  Wheat  or potatoes
  46. 46.  are an exception:
  47. 47. Soya bean protein is a good source of protein, for vegetarians and vegans or for people who cannot afford meat. Explain.
  48. 48. Have you ever tasted:  Soya bean milk  Tofu Tofu is made by coagulating soya milk and then pressing the resulting curds into soft white blocks.
  49. 49.  is referred to as:
  50. 50. Artificial meat is manufactured from :  soya beans  bacteria and fungi Artificial meat is flavoured and textured to taste like chicken or ham.
  51. 51. How can protein deficiency from a vegetarian diet be avoided? By eating a combination of plant foods that complement each other to supply all essential amino acids.
  52. 52.  For example, beans supply the lysine that is missing in corn, and corn provides the methionine which is deficient in beans.
  53. 53. Excess proteins:  cannot be stored in the body  are broken down in the liver by a process called DEAMINATION  the waste product produced is called UREA liver
  54. 54. Components of a balanced diet :1. 2. 3. 4. 5. 6. 7. Water Carbohydrates Lipids Proteins Mineral salts Vitamins Dietary fibre or roughage
  55. 55. MINERAL SALTS  contain certain elements that help cells to function properly
  56. 56. CALCIUM  is needed for:a) hard bones and teeth b) muscles to contract c) to clot blood  is found in:  milk  cheese  fish
  57. 57. Rickets: deformed bones  deficiency of calcium
  58. 58. IRON  is needed to build the red pigment in blood called haemoglobin
  59. 59. IRON  is found in:  red meat like liver & kidneys  green vegetables: spinach, broccoli
  60. 60. A lack of iron results in: ANAEMIA Normal amount of red blood cells Anaemic amount of red blood cells
  61. 61. Question: MAY, 2004 Give biological explanations for each of the following statements: a) A dietician suggested to an anaemic person to include liver in the diet. (5) Person lacks iron. Red meat like liver is rich in iron. Iron is needed to form haemoglobin in red blood cells.
  62. 62. b) Nutritionists often recommend a low intake of fried foods. (5)  Fats provide a lot of energy. May lead to obesity.  Fried foods are rich in cholesterol that may block arteries = higher risk for a heart attack.
  63. 63. MAGNESIUM  forms the centre of the chlorophyll molecule in green plants No magnesium: yellow leaves
  64. 64. Components of a balanced diet :1. 2. 3. 4. 5. 6. 7. Water Carbohydrates Lipids Proteins Mineral salts Vitamins Dietary fibre or roughage
  65. 65. VITAMINS  needed in small quantities for the normal chemical activities of the body  cannot be used as:  a source of energy OR  to build cell structures
  66. 66. A disease develops if a vitamin is missing. How can the person be cured? By taking the missing vitamin.
  67. 67.  vitamins can be :a) Water soluble – vitamins B and C b) Fat soluble – vitamins A, D, E, K
  68. 68. Why is it better to steam vegetables rather than boil them? Water-soluble vitamins are lost from the vegetables when they are boiled but not when steamed.
  69. 69. Vitamin Food source A Milk, liver C Citrus fruit, potatoes Milk, liver D Deficiency disease Night blindness Scurvy Rickets
  70. 70. Carrots are a rich source of vitamin A Vitamin A prevents night blindness.
  71. 71. QUESTION: MAY 2010 Explain why the student used this picture when mentioning night blindness. (2) Night blindness is caused by a lack of Vitamin A in the diet. 1 mark Carrots are a good source of Vitamin A that can help to prevent night blindness. 1 mark
  72. 72. Found in Citrus fruit
  73. 73. Deficiency of Vitamin C:
  74. 74. Which vitamin prevents colds?
  75. 75. Vitamin D is made by the action of sunlight on the skin. Normal Deficiency of Vitamin D: Rickets
  76. 76. NOTE:  Lack of calcium  Lack of vitamin D Reason: Vitamin D helps the body to absorb calcium from the foods we eat. The more calcium the body can absorb, the stronger the bones will become
  77. 77. Question: Sep, 2004 What special provisions should be made in the diet of young children and pregnant mothers? Explain why each provision you mention is important. (6, 4) Young children: 1. High protein content food – e.g. meat for growth 2. Drink a lot of milk – supplies proteins, calcium, Vitamin A & D. 3. Include carbohydrate-rich foods – for energy
  78. 78. Pregnant women: 1. Folic acid (a vitamin B) – in citrus fruit, legumes: to form the nervous system of the embryo 2. Food rich in iron – e.g. liver, green vegetables: to have enough blood in placenta to nourish embryo 3. Calcium-rich food – e.g. dairy products to supply embryo with calcium to form its skeleton
  79. 79. Question: Sep, 2004 Give a biological explanation for each of the following statements. a) Daily inclusion of too much Vitamin C in the diet is a waste. (2) Vitamin C cannot be stored in the body as it is water-soluble. Lost in urine.
  80. 80. Give a biological explanation for each of the following statements. a) Small doses of Vitamin D (5-10mg per day) are recommended for housebound people spending a lot of time indoors. (2) Vitamin D cannot be made by the action of sunlight on the skin. To have enough Vitamin D, supplements are needed.
  81. 81. Question: MAY, 2004 Give biological explanations for each of the following statements: a) School canteens are encouraged to sell unsweetened cereals rather than sweets. (5) Sweets are carbohydrates that provide energy. Too much sweets may lead to obesity. Obesity leads to higher risk of diseases. Sweets increase chance for tooth decay.
  82. 82. b) Young children are encouraged to eat dairy products regularly. (5) Milk is rich in:  calcium – needed to form strong bones and teeth.  proteins – needed for growth.  Vitamins – for healthy growth; e.g. vitamin A to prevent night blindness and vitamin D to help in the absorption of calcium and to prevent rickets.
  83. 83. Components of a balanced diet :1. 2. 3. 4. 5. 6. 7. Water Carbohydrates Lipids Proteins Mineral salts Vitamins Dietary fibre or roughage
  84. 84. DIETARY FIBRE or ROUGHAGE  sources of fibre: vegetables  fresh fruit  bran cereals  wholemeal bread
  85. 85. Cellulose : is the main source of dietary fibre Explain why although humans cannot digest dietary fibre, it is still important.
  86. 86. Functions of roughage:1. adds bulk to the contents of the intestine and keeps food moving along the gut Gut
  87. 87. Functions of roughage:2. prevents constipation as fibre retains water so that the faeces are soft 3. prevents cancer of the colon (part of the intestine) faeces
  88. 88. Food Starch Iodine solution Starch Test + iodine solution Colour change Yellow to blue black
  89. 89. Look at this picture. Is starch present in potato? Yes.
  90. 90. Food Test + sodium hydroxide solution + Protein 1-2 drops of copper sulfate (Biuret test) solution 2. Copper sulfate solution 1. Sodium hydroxide solution Egg white [protein] Colour change Blue to purple
  91. 91. A positive test for protein was obtained albumin for………………
  92. 92. Food Oil Test Colour change + ethanol + shake + water + A white emulsion shake forms
  93. 93. Food Test Colour change Oil rub food onto a dry piece of filter paper A greasy spot forms
  94. 94. Food Glucose Test + Benedict’s solution Fehling’s solution + heat Colour change or Blue to brick red or orange
  95. 95. Food Glucose Test + Benedict’s solution Fehling’s solution + heat Colour change or Blue to brick red or orange
  96. 96. Food Starch Colour change Test Yellow to blue black + iodine solution + sodium hydroxide solution + Protein 1-2 drops of copper sulfate (Biuret test) solution Blue to purple 1) + ethanol + shake + water + A white emulsion shake forms Oil 1) rub food onto a dry piece of filter paper Glucose + Benedict’s solution Fehling’s solution + heat A greasy spot forms or Blue to brick red or orange
  97. 97. When the food to be tested is a solid: 1. Crush the food with some water using a pestle and a mortar. 2. Filter. 3. Add the reagents to the filtrate. pestle mortar
  98. 98. How do you find how much energy is present in a peanut?  Burn a peanut  Record rise in temperature of a known volume of water.
  99. 99. Why is it better to have a larger volume of water? To absorb more heat.
  100. 100. Q = mc Heat energy = mass x specific heat capacity x temperature rise Energy in peanut = mass of water x 4.2 x temperature rise in C 1000 4.2 kJ kg-1 C-1 1000: to work mass in kg
  101. 101. Question: MAY, 2011 [IIB] A group of biology students would like to compare the energy stored in two types of nuts: a peanut and an almond. Describe an experiment to show how this is carried out. In your report include: i) The apparatus required; (You can present this in the form of a diagram.) (2)
  102. 102. ii) The method; (3) Known quantity of the nut (kept constant for both nuts) ignited and held under test tube with known amount of water (kept constant for both nuts). The temperature of water before lighting the nut and after burning will be recorded. iii) The measurements that need to be taken;  Initial temperature and final temperature  Mass of peanut/almond  Volume of water (2)
  103. 103. iv) The factors that need to be kept constant throughout the experiment; (2) Same mass of nut and same quantity of water. v) ONE possible source of error. (1)  Heat loss to surroundings  Heat reaching water not evenly spread out  Burning of nut is not complete
  104. 104. How is the energy content of food found out? Burning food in a bomb calorimeter.
  105. 105. Bomb Calorimeter The apparatus which is used to find the energy content of food. Better than previous setup: 1. No heat loss to air. 2. Even heat spread.
  106. 106. The End

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