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  1. 1. NUTRIENTS • Why do we need food? • Nutrients in food. • Structure of large molecule. • Food Test.
  2. 2. WHY DO WE NEED FOOD? • We need food to give us ENERGY • We need food to keep us HEALTHY • We need food to REPAIR and REPLACE damaged and worn out Tissues • We need food to GROW
  3. 3. NUTRIENTS IN FOOD • Carbohydrates • Proteins • Fats ( lipids) • Vitamins • Mineral Salts
  4. 4. CARBOHYDRATES Simple sugars Structure ( what are they made of) Complex sugars Polysaccharides Made up of simple units Made up of two simple sugar joined together. e.g. MALTOSE, SUCROSE Glucose + Glucose Made up of many simple sugars joined together e.g. GLUCOSE Maltose + Water e.g. Starch, Glycogen e.g. FRUCTOSE Many glucose molecules Glucose + Fructose Sucrose + Water One starch molecule + many water molecules
  5. 5. Simple sugars Complex sugars Polysaccharides Sources Sweet, honey, fruits, jam Sugar cane, malted cereals Rice noodles, potatoes, cakes, cereals, vegetables. Function in the body • Supply energy • Form nucleic acids ( DNA) • Make lubricant ( mucus) Effects of too • Become fat as excess carbohydrates are converted to much on the fat and stored body Effect of too little on the body • Become very weak and will not grow
  6. 6. PROTEINS Structure • Made up of many amino acids joined together ( what are they made of) e.g Many amino acids one protein molecule + many water molecules • There are about 20 amino acids found in the structure of protein. • Many amino acids link up to form a polypeptide. • One or more polypeptides link up to form protein molecule. Source Lean meat, fish, milk, cheese, egg white, peas, beancurd, nuts. Function in body • Form protoplasm for making new cells so that the body will grow. • Repair and replace damaged and worn out tissues. • Make enzymes and hormones. • Form antibodies. • Supply energy Effect of too little on the body • Muscles are poorly developed • Become very weak and will not grow
  7. 7. FATS Structure ( what are they made of) • Made up fatty acids and glycerol e.g 3 molecules of fatty acid + 1 molecule of glycerol 1 molecule of fat + 2 water molecule. Source Oil, butter, full cream milk, fatty meat, nuts sunflower seeds. Function in body • • • • • Effect of too much on the body • Becomes fast as excess fats are stored Effect of too little on the body • Muscles are poorly developed • Become very weak and will not grow Supply energy Form part of cell surface membrane Insulate against heat loss Act as solvent for fat soluble vitamins and hormones Prevent water loss.
  8. 8. WATER • Water is used as a SOLVENT in living organism. • Water is important for REGULATING THE TEMPERATURE OF ORGANISM. • Water plays a role in SUPPORTING STRUCTURES AS ORGANISMS. • Water plays a role in LUBRICATION • Water plays a role in METABOLISM. • Water plays a role in the DISPERSAL OF FRUITS.
  9. 9. Food Test Test for starch – IODINE TEST • Add one or two drops of dilute iodine solution to the food sample. • A BLUISH - BLACK colour indicates the presence of starch • If starch is absent the iodine solution remains BROWN
  10. 10. Test for reducing sugar – BENEDICT’S TEST • Make a solution of the food sample. • Add an equal amount of Benedict’s solution (copper II salt ( blue)) to 2 ml of the food solution. • Mix well and place the tube in a boiling water bath for two minutes. • Colour of the solution changes to green yellow to red ( copper I oxide (red)). • Colour changes indicates the presence of reducing sugar
  11. 11. Test for protein- BIURET TEST • Make a solution of the food sample. • Add an equal volume of 5% sodium hydroxide solution to 2 ml the food solution. • Shake the tube to mix the content. • Add 1% of copper (II) sulphate solution a drop at a time, shaking the tube after each drop. • A violet colour indicates the presence of protein while a light blue indicates the absence of the protein.
  12. 12. Test for fats – ETHANOL EMULSION TEST • Grind food items and put it into a test tube. Use only two drops of the food items if it is liquid. • Add 2ml of ethanol and mix well. Allow any solid particles to settle. • Decant the ethanol into another test tube containing2 ml of water. • Mix well and look for a WHITE EMULSION ( CLOUDINESS) Lipids are present . • Clear solution absence of lipids