Food and digestion Food Balancing your diet Digestion 8A Food and digestion Food and digestion Food Balancing your diet Digestion Reference: The Heinemann Science Scheme – Book 3

8A Food and digestion Food

8A Food – who needs it? What do we need food for? Energy to do things Raw materials to grow larger Raw materials to repair damaged body parts

8A So what’s in food? Food is a complicated mixture of different chemicals. We can sort these chemicals into different types. What are the main types? Proteins Vitamins Fats Minerals Water Fibre Carbohydrates (starch and sugars)

8A Which food contains which chemical? Which foods belong to which food groups? Proteins Water Fats Carbohydrates Proteins Fats Carbohydrates Water

Vitamin Found in Gives you 8A Vitamins A Liver, butter, green vegetables Healthy skin and teeth Cheese, milk, liver, eggs, green vegetables Healthy skin B2 Citrus fruits, green vegetables, potatoes Healthy teeth and gums, without it you get scurvy C Fish liver oil, eggs, sunlight on the skin Healthy bones – without it you get rickets (soft bones) D

8A Food and digestion Balancing your diet

8A A food test for YOU! 1. A balanced diet… a) contains the same amounts of the main food groups b) contains healthy amounts of the main food groups c) doesn’t fall off the table. 2. A balanced diet for most people has more… a) fat than water b) carbohydrate than protein c) crisps than fruit.

8A A food test for YOU! 3. To test for protein in food you… a) add iodine solution b) do the Biuret test c) poke it with a big stick. 4. Sugar and starch are both… a) proteins b) fats c) carbohydrates.

8A A food test for YOU! 5. Iodine solutions turns blue-black with… a) starch b) protein c) age. 6. A food went orangey-red when it was boiled with Benedicts solution. It could be… a) a carrot b) a boiled sweet c) a sausage.

8A A food test for YOU! 7. Not enough vitamin C gives you… a) headaches b) scurvy c) weak bones. 8. Riboflavin is… a) a B vitamin b) a fruit drink c) an elf from The Lord of the Rings.

8A Food and digestion Digestion

Chewing food breaks it down into smaller pieces Chewing food breaks it down into smaller pieces. Breaking food into smaller pieces is called digestion. To help breakdown particles of starch, protein and fat, the digestive system also releases chemicals called ENZYMES. Enzymes are like very tiny scissors which breaks large particles into smaller particles. Enzymes are not living things. They are just special proteins that can break large molecules into small molecules. Different types of enzymes can break down different nutrients: carbohydrates or amylase enzymes break down starch into sugar protease enzymes break down proteins into amino acids lipase enzymes break down fats into fatty acids and glycerol.

What affects enzyme action? The conditions inside the digestive system can affect how quickly food is digested. Different enzymes work best in different conditions. Enzymes in the stomach work best in acidic conditions. The stomach makes hydrolic acid to keep its enzymes working properly. Enzymes in small intestine work best in alkaline conditions. The small intestine makes alkali to keep its enzymes working properly. All the enzymes in the body work best at body temperature about (37 centigrade).

8A Why digestion? Food is a mixture of molecules. Some of these molecules are too large to pass into the body. Digestion breaks down food in the gut into smaller molecules. The body uses these smaller molecules for energy or to build body parts.

Mouth breaks large lumps of food into smaller lumps. 8A Where it all happens What happens where? Follow the food down through the body. Mouth breaks large lumps of food into smaller lumps. Stomach produces enzymes to break down proteins. Intestines produce enzymes to break down proteins, carbohydrates and fats. Start to absorb food into body. Colon absorbs water and stores waste until time to pass out of the body.