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Key words: nutrients carbohydrates molars canines stomach absorption proteins vitamins saliva pancreas duodenum anorexia minerals lipids obesity enzyme appendix bulimia starch roughage gall bladder ingestion rectum glucose malnutrition incisors small intestine large intestine villi bile anus liver ileum Key definitions to learn: Balanced diet Food tests Energy requirements Energy intake Digestion Peristalsis Absorption A diet containing correct balance of different nutrients Tests carried out on food samples to determine their makeup Energy needs depending on age, sex, and level of activity Calculation of energy obtained from eaten food Breaking food down Movement of food by muscular contractions down oesophagus Food molecules taken through the wall of the small intestine Key Learning Points: Food is needed to provide our bodies with nutrients and energy Energy and nutrients are needed to make new cells and tissue for growth and repair old and damaged cells and tissue. Energy and nutrients are also needed to make our muscles work. A balanced diet must contain sufficient amount of all the food groups as well as the correct amount of energy. See table of nutrients – later Malnutrition occurs when a person is not getting all the necessary food groups in their diet. Obesity is when a person is 25% over weight. Anorexia nervosa is loss of appetite because a person thinks they are overweight. Bulimia usually involves eating food then bringing it up again. Kilojoule (kJ) is the unit of food energy. Different foods provide different amount of energy. Types of Teeth Incisors Canines the sharp, chisel-shaped front teeth used for cutting food. these teeth are shaped like points (cusps) and are used for tearing food. Premolars these teeth have two pointed cusps on their biting surface and are sometimes referred to as bicuspids. The premolars are used for both crushing and tearing. used for grinding, these teeth have several cusps on the biting surface Molars The major nutrient groups are: Nutrient Group Carbohydrates (Starch and Glucose) Found in Needed potato, pasta, cakes, breads and biscuits as the main source of energy for the body Lipids (fats) fatty meats, cream, butter and cooking oil, as a source of energy, and insulation for the body Proteins Vitamins and minerals Water Food Test test for starch by goes black if starch adding iodine to food sample test for glucose by adding Benedict’s solution to food sample and heat, test for lipids (fat) by adding 1ml of ethanol to food sample then 1ml water or rub fat onto paper is present goes orange, yellow or green depending upon the concentration of glucose that is present cloudy white solid forms if lipids present. test for by adding meat, fish, eggs, cheese, milk and seeds for body growth and repair in many foods, especially fruit and vegetables found in most drinks in small amounts for the bodies chemical reactions to live. Without water, we cannot live for more than 7 days. Water makes up about 60% of our body cells. Most of the chemicals in our body are dissolved in water, or are suspended in water. Digestive System Be able to label the major organs associated with digestion. Result sodium hydroxide and copper sulphate solution to pureed food (Biuret test) fat causes greasy stain goes purple colour if protein present Chewing is the first of digestion, it involves the teeth biting, chewing and shaping the food, with the help of the tongue. Saliva, containing the enzyme amylase/ptyalin, is added to start breaking down starch and to make the food easily swallowed. Muscle contractions called peristalsis moves the food along down the digestive system. The purpose of the stomach is to physically churn and break down the food using special chemicals and to slowly release the contents into the small intestine. The first part of the small intestine is the duodenum, here the food is showered with enzymes from the pancreas and bile from the gall bladder, these break down the food further. The ileum is the site of absorption. It is lined with small finger like extensions called villi. These increase the surface area so that rapid absorption can occur. As food passes along the large intestine excess water is reabsorbed back into the blood stream. Finally the waste food (faeces) passes into the rectum and remains there until expelled through the anus. Food Tests Food Type Starch Description of Test Add a few drops of iodine solution Observation of a positive result Turns from yellow to blue-black Glucose Add a few drops of Benedict’s solution and heat gently Add 5mLs of sodium hydroxide then a few drops of copper sulfate Rub between a piece of filter paper Turns from blue to green, yellow, orange or brick red Turns from blue to mauve (light purple) Protein Fats and oils Leaves a grease stain on the paper Model Gut Website URL for revision: http://www.sciencepages.co.uk/keystage3/year8/module13/m13revision.php Revision Questions: 1. What are the main food groups? …………………………………………………………………………………………………… 2. Which food provides instant energy? …………………………………………….…… 3. Which food provides slow release energy? …………………………………………… 4. Which mineral is needed for bone growth? ……………………………………………. 5. Which food is high in vitamin C? ……….…………………………………………. 6. What is digestion? …………………………………………………………………………………………………… …………………………………………………………………………………………………… …………………………………………………………………………………………………… 7. What is absorption? …………………………………………………………………………………………………… …………………………………………………………………………………………………… 8. What are your incisors used for? ………………………………………………………… 9. What are your molars used for? ………………………………………………………… 10. What is the function of the stomach? …………………………………………………………………………………………………… …………………………………………………………………………………………………… …………………………………………………………………………………………………… …………………………………………………………………………………………………… …………………………………………………………………………………………………… 11. What purpose does the gall bladder have in digestion? …………………………………………………………………………………………………… …………………………………………………………………………………………………… 12. Model Gut Investigation: We found that the starch solution turned Iodine from yellow brown to …………………., but the Benedict’s stayed ……………… . This confirms that the solution contained ……………… but did not contain ……………… . The glucose solution turned ………………….. from blue to brick red when ……………. but did not turn the yellow brown ………………. blue-black. This confirms that the solution contained ……………… but did not contain ………………… . The water from the beaker …………… the tubing was added changed the ……………. of neither Iodine nor Benedict’s. ………………… the water contained neither starch nor glucose. However, …………… the tubing had soaked in the beaker of …………… for 2O minthe water did not change the colour of …………………. but changed the colour of …………………….. solution from blue to orange. This is …………………. that glucose has moved from …………… the dialysis tubing into the water but the starch ……….. …………. . Benedict’s starch inside blue-black before glucose Therefore evidence after starch colour water heated Benedict’s blue Iodine glucose did not Iodine yellow-brown Draw a mindmap for this unit: Add to it, as you develop your learning. Food and Digestion Well done you have completed another revision unit. Now reflect on how you can improve further: Which aspects of the unit do I need to revise more carefully? Which aspects of the unit do I need help with? How will I seek this help? Answers to Food and Digestion Revision Question 1. Carbohydrates, lipids (fats), proteins. (Food also provides essential vitamins and minerals). 2. Carbohydrate in the form of glucose which is absorbed instantly into the blood stream. Starch has to be broken down (digested) first. 3. Carbohydrate in the form of starch. It releases energy as it is slowly broken down. 4. Calcium. 5. Citrus fruits e.g. oranges and lemons. 6. The breakdown of large molecules into smaller molecules using enzymes. 7. The passage of small molecules resulting from digestion through the cell membrane of the villi lining the small intestine 8. Cutting food / Snipping off portions of food 9. Grinding food 10. Store the food, mechanically break it down by churning it up and to add acid and digestive enzymes to begin digestion (not to digest food). 11. Stores bile which is used to help digest lipids (fats). i.e. it emulsifies the fat droplets, breaking them down and increasing the surface area for enzymes to act on. 12. We found that the starch solution turned Iodine from yellow brown to blue-black, but the Benedict’s stayed blue. This confirms that the solution contained starch but did not contain glucose. The glucose solution turned Benedict’s from blue to brick red when heated but did not turn the yellow brown Iodine blue-black. This confirms that the solution contained glucose but did not contain starch. The water from the beaker before the tubing was added changed the colour of neither Iodine nor Benedict’s. Therefore the water contained neither starch nor glucose. However, after the tubing had soaked in the beaker of water for 20 min the water did not change the colour of Iodine but changed the colour of Benedict’s solution from blue to orange. This is evidence that glucose has moved from inside the dialysis tubing into the water but the starch did not.