Food and Digestion

1. Food and Digestion W Richards The Weald School

2. Food types Bread, potatoes, cereal Energy Cream, butter, milk, oil A store of energy Meat, fish, eggs Building and repairing cells Vegetables, cereal Keep things “ticking over” Meat, milk, cereal Strong teeth etc Fruit + veg, cereal Keeps you regular! Water! 75% of the body is water

3. Food tests 1 Iodine To investigate what happens in digestion we need to be able to test for different foods. Here are two simple tests: • The test for starch: • Drop some iodine onto the food. If the iodine turns BLUE/BLACK then STARCH is present. • The test for simple sugars (e..g glucose) • Boil the food with some Benedict’s solution. If an orange “precipitate” appears then the food contains simple sugars

4. Food tests 2 • The test for protein: • Add 5cm3 of dilute sodium hydroxide followed by 5cm3 of dilute copper sulphate. If protein is present it will produce a purple colour. • The test for fats: • Shake the food with about 10cm3 of ethanol in a test tube. Pour some of the solution into a tube containing water. If fat is present the water will turn cloudy white.

5. The digestive system The whole point of digestion is to break down our food so that we can get the bits we need from it… The main foods affected are CARBOHYDRATES – these are broken down into GLUCOSE

6. Enzymes Enzymes are chemicals produced by the body to help _______. When they react with food they break it down into ______ pieces which can then pass into the ______: Carbohydrase breaks _______ (a carbohydrate) down into glucose: Protease breaks _______ down into amino acids: Lipase breaks fats (_____) down into fatty acids and glycerol: Words – blood, lipids, proteins, digestion, starch, smaller

7. The small intestine Everything else passes into the large intestine Glucose gets absorbed into the blood This is where the “small parts” are absorbed into our blood stream…