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Food Food
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Why do living things need food?
1. As a material for growth 2. To give us energy
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How do living things get food?
Don’t need to take this down Plants use sunlight to make their own food “Photosynthesis” Animals eat plants and other animals
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A balanced diet has six constituents
Carbohydrates Proteins Fats Vitamins Minerals Water They all have different functions so we need them all, but in different amounts
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A Food pyramid tells us the number of servings of each of the food groups that we should eat each day
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Rarely Fats, Oils, Cakes, Sweets Dairy Products 2 servings a day Meat and Fish Vegetables 4 servings a day Fruit Cereals 6 servings a day 8 servings a day Water
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1. Carbohydrates - Sugar Sugar is a type of carbohydrate
The function of sugar is to provide energy If a simple sugar is present in a food it will turn Benedict's solution from blue to red
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To test for the presence of a sugar
Stand the test tubes in hot water for about 3 minutes. If sugar is present in a food it will turn Benedict's solution from blue to red
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Testing different types of food for the presence of a simple sugar
How can you make sure that the test is fair? What control could you use for comparison to the real experiment?
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Sources of sugar: Honey Jam Fizzy drinks Cakes
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2. Carbohydrate - Starch Starch is a type of carbohydrate
The function of starch is to provide energy Starch will change iodine from a brown/yellow colour to a blue colour
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To test for the presence of starch
Iodine turns from yellow/brown to blue if starch is present
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Source of starch Bread Potato Pasta Rice
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3. Carbohydrate - Fibre Fibre is a type of carbohydrate
The function of fibre is to help prevent constipation It is found in green vegetables and cereals
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Fat The function of fat is in our diet is to: Provide us with energy
Store energy Provide us with insulation
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A special test for the presence of fat
Fat makes brown paper go translucent (light passes through it very easily)
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Sources of fat Oil Butter Milk Cheese
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Protein The functions ( job) of protein in our diet is:
To make muscle, hair, hormones and enzymes
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To test for the presence of protein in food:
Dissolve the food in some water. Add some biuret solution to the test tube. If protein is present the solution will turn from a blue to a purple colour!
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Sources of protein Milk Nuts Eggs Meat Cheese
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Water (H20) The function of water in our diet:
It is an excellent solvent and so it helps things to be transported around the body Sources of water: Drinks
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Vitamins Vitamin C Keeps gums and skin healthy Source: Fruit
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Scurvy – not enough vitamin C
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Vitamin D builds strong bones and teeth Source: Milk, cheese, yogurt
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Rickets – not enough vitamin D
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Minerals Iron is needed to make red blood cells Source:
Red meat, cabbage
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Minerals Calcium For healthy bones and teeth Source:
Milk, cheese, yogurt
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