1. A balanced diet and the 7 food groups Aims: –To know why food is important –To know that a healthy diet consists of a balance of 6 groups of chemicals and water –To be able to use chemical tests to identify proteins, carbohydrates and fats

2. Diet Your diet is the food you eat every day. You could have a poor diet or a healthy diet. Your food is a source of raw materials for your body. These raw materials are needed to make new substances for: –Energy –Growth –Health

3. Humans need to consume a balanced diet which contains a variety of different types of food. The main nutrients the body needs are: carbohydrates for energy; proteins for growth and repair; fats to store energy; vitamins and minerals to keep the body healthy; fibre to keep your intestines healthy and prevent constipation; water is an important solvent in your body. It has many used. Why do we need food? The amount of each food type needed is related to the proportions in the food pyramid. Which food type does the body need the most of?

4. Nutrients in food

5. What is a balanced diet?

6. Starchy foods contain carbohydrates which are made of long chains of identical small sugar molecules. carbohydrate molecule What are carbohydrates? one sugar molecule The long chains of carbohydrates are broken down into the smaller sugar molecules by the body. The small molecules from carbohydrates are used by the body to release energy and make the body work.

7. Proteins, like carbohydrates, are made of long chains of small molecules. In proteins, these small molecules are not identical. What are proteins? protein molecule one amino acid Proteins are made up of chains of small molecules called amino acids. There are over 20 different kinds of amino acid. Proteins are used by the body for growth and repair.

8. Fats are made up of fat molecules which contain fatty acids and glycerol. What are fats? fat molecule glycerol Fat molecules have to be broken down by the body so that they can be used for energy storage. Fats are also used by the body to keep heat in and to make cell membranes. fatty acids

9. Food typesType Found in Uses Carbohydrates Fats Proteins Vitamins Minerals Fibre Water

10. Food typesType Found in Uses Carbohydrates Fats Proteins Vitamins Minerals Fibre Water Bread, potatoes, cereal Cream, butter, milk, oil Meat, fish, eggs Vegetables, cereal Meat, milk, cereal Fruit + veg, cereal Water! Energy A store of energy Building and repairing cells Keep things “ticking over” Strong teeth etc 75% of the body is water Keeps you regular!

11. What problems can diet cause? Too much food: –Weight gain –Heart disease Too little food: –Weight loss –Lack of energy Too little protein: –Muscle wastage –Kwashiorkor

12. What problems can diet cause? Too little vitamin C: –Scurvy Too little vitamin D: –Rickets Too little calcium: –Weak bones and teeth

13. Food tests 1 To investigate what happens in digestion we need to be able to test for different foods. Here are two simple tests: 1)The test for starch: Drop some iodine onto the food. If the iodine turns BLUE/BLACK then STARCH is present. 2)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 Iodine

14. Food tests 2 1)The test for protein: Place 1 cm of food at the bottom of a test tube. Add 5 drops of Biuret solution. If protein is present it will turn lilac/purple 2)The test for fats: Shake the food with about 10cm 3 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.