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Human Nutrition

Human Nutrition. WJEC Additional Science Module 2. Animal Nutrition. Learning Objectives (the big picture) By the end of this topic, you should be able to answer the questions Why is digestion needed? How does the digestive system work? What happens to the end products?.

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Human Nutrition

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  1. Human Nutrition WJEC Additional Science Module 2

  2. Animal Nutrition • Learning Objectives (the big picture) • By the end of this topic, you should be able to answer the questions • Why is digestion needed? • How does the digestive system work? • What happens to the end products?

  3. Learning outcomes • know that fats, made up of fatty acids and glycerol, proteins, made up of amino acids, and starch (a carbohydrate), made up of a chain of glucose, in our food are insoluble. They are broken down during digestion into soluble substances so that they can be absorbed through the wall of the small intestine into the bloodstream. • Consider the use of visking tubing as a model gut and the limitations of the model.

  4. Learning outcomes • recognise and label on a given diagram of the human digestive system and associated structures: the mouth, oesophagus/gullet, stomach, pancreas, small intestine, large intestine, anus and understand the role of the following organs in digestion: mouth, stomach, pancreas, small intestine.

  5. Learning outcomes • know that during digestion, the breakdown of large molecules into smaller molecules is carried out by enzymes which are specific for each type of molecule. • know that the body cells need the digested products of fats and carbohydrates to provide energy whilst amino acids are needed to build proteins in the body

  6. Quick Revision • A balanced diet must contain all the essential nutrients in the correct amounts and proportions. • The nutrients needed are • Carbohydrate • Fat • Protein • Vitamins • Minerals • Fibre • Water.

  7. Main Nutrients

  8. What you really need to remember!! • Carbohydrates, fats and proteins are all made up of the elements carbon, hydrogen and oxygen • Proteins always contain nitrogen and sometimes sulphur • One way to remember this is • Carb O Hydrate

  9. Carbohydrates • Large carbohydrate molecules such as starch and glycogen are made up of long chains of smaller units, e.g. glucose, which are held together by chemical bonds

  10. Fats • Fats are made up of three fatty acids and a glycerol

  11. Proteins • Proteins are made up of long chains of amino acids

  12. Food Tests • What is the test for starch? • What is the test for glucose? • What is the test for protein? • What is the test for fats? • What does a positive result look like?

  13. Carbohydrates • Carbohydrates give us energy. • Chemical elements – C, H and O. • Starch is made from simple sugars.

  14. Testing for glucose • Pour some glucose solution into a test tube • Add a few drops of benedict's solution • Heat in a water bath

  15. Testing For Starch • Put a few drops of starch solution on a spotting tile. • Add a few drops of iodine.

  16. Proteins • Proteins are needed for growth and repair. • Proteins are made from amino acids • Chemical elements – C, H, O, N (and S)

  17. Testing for Proteins • Put 2 ml of protein solution in a test tube • Add 2ml of Biurets reagent

  18. Fats • Fats are an energy store, protecting vital organs and providing insulation. • Fats contain C, H and O • Fats are made from a glycerol molecule and three fatty acids.

  19. Testing for fat (the emulsion test) • Add a few drops of cooking oil into a test tube • Add 2cm3 ethanol and shake • Add 2cm3 water and shake again.

  20. Mystery Foods • Test the three “mystery food” samples • Which food substances are present in each one?

  21. Pupil activity • Design a mind map to summarise the information on basic nutrition

  22. Learning Outcomes • identify the gross structure of the alimentary canal and associated organs (mouth, oesophagus, stomach, small intestine: duodenum and ileum, large intestine: colon and rectum, anus, pancreas, liver) • define ingestion, digestion, absorption, assimilation and egestion

  23. What happens to the food we eat? Ingestion Digestion Absorption Egestion

  24. The gut as a production line

  25. What happens to the food we eat? • Ingestion • Intake of food into the mouth • Digestion • Breaking down large, insoluble food molecules into smaller soluble ones using enzymes

  26. Absorption • Digested food molecules pass across the wall of the small intestine into the blood or the lymph • Assimilation • Uptake of food molecules by cells

  27. Egestion • Passing out of undigested food, in the form of faeces, from the anus • Deamination • Removal of nitrogen containing part of an amino acid as urea.

  28. Pupil Activity • Label the diagram of the digestive system. • Use the textbook supplied to help if needed • Design a table to link the structure and function of different parts of the digestive system.

  29. Salivary glands mouth oesophagus tongue trachea liver stomach Gall bladder pancreas Small intestine Duodenum ileum colon Large intestine rectum appendix anus

  30. Learning Outcomes • define ingestion, digestion, absorption, assimilation and egestion • describe the functions of the alimentary canal's various parts in relation to ingestion, digestion, absorption, assimilation and egestion of food

  31. Digestion • Digestion is the breakdown of large, insoluble food molecules into small, soluble food molecules so that they can be absorbed into the blood stream.

  32. Digestion of Food • The digestion of food can either be mechanical or chemical. • Mechanical digestion includes • Chewing • Action of muscles in oesophagus, stomach and small intestine • In chemical digestion enzymes catalyse the breakdown of larger food molecules into smaller food molecules.

  33. Digestion in the mouth and oesophagus • Chewed food is mixed with saliva in the mouth • Saliva contains • Amylase is an enzyme which starts to digest starch into sugars (maltose) • Mucus helps soften the food making it easier to swallow • The bolus travels down the oesophagus with the aid of peristalsis

  34. Peristalsis in the gullet

  35. Digestion of Starch • Take 10ml of 1% starch solution • Test for starch • Test for sugars

  36. Action of amylase on starch • Put a drop of iodine solution into all the wells on a white spotting tile • Add 10ml 1% starch solution and 10ml 1% amylase solution to a test tube. • Every minute, test the contents of the test tube for starch. • After 15 minutes – test the solution for the presence of sugars • Write a conclusion on your results

  37. Learning Outcomes • The significance of producing small, soluble molecules • describe: • digestion in the alimentary canal • the functions of a typical amylase, protease and lipase, listing the substrate and end-products

  38. Digestion • Digestion is the breakdown of large, insoluble food molecules into small, soluble food molecules by enzymes, so that they can be absorbed into the blood stream.

  39. Digestion • Physical Digestion • Increases the surface area of food • Chewing in the mouth • Churning food in stomach and small intestine • Bile emulsifies fats – turns them into smaller droplets with a larger surface area

  40. Digestion • Chemical Digestion • Breakdown of large insoluble molecules into smaller soluble ones • Enzymes act as biological catalysts – they speed up the process • They work efficiently at body temperature (37OC) and at a suitable pH

  41. Digestive enzymes • There are different types of digestive enzyme • Proteases break down proteins into amino acids • Lipases break down fats into fatty acids and glycerol • Amylase breaks down starch into maltose (sugar) • Maltose is then broken down by maltase to form glucose

  42. Summary – digestive enzymes

  43. Chemical Digestion • Hydrogen carbonate ions • Secreted by pancreas • Neutralises acid, enabling enzymes in small intestine to work  • Bile • Produced by liver, stored in gall bladder, secreted into small intestine • Emulsifies fats (Larger surface area for enzymes to work on)

  44. Prep • Surface area and digestion • Read the information • Answer questions 1- 3 • Answer question Ho2 • A snake swallowed a mouse whole. Explain why it took several days to digest it.

  45. Learning Outcomes • define the term catalyst • define enzymes as proteins that function as biological catalysts • describe the effect of changes in temperature and pH on enzyme activity

  46. Enzymes Revision • Are proteins • Are produced by cells • Change chemical substances into new products • Are “specific” to one substance • Work best at their “optimum temperature” (around 30 – 40oC) • Work best at an optimum pH

  47. Protein Digestion • Protein digestion occurs in the stomach and small intestine. • Protease enzymes are produced by the gastric pits in the stomach lining or by the pancreas. • In the stomach, hydrochloric acid is also produced which provides the optimum pH for trypsin to work

  48. Protein Digestion • Add 2ml of protein solution to three test tubes. • Number the test tubes 1, 2 and 3 • Add 1ml HCl • Add 1ml Water • Add 1ml HCl • Do not add the trypsin until last • Add 0.5ml water • Add 0.5ml trypsin • Add 0.5ml trypsin

  49. Protein digestion • Leave for 10 minutes • Test each of the test tubes for the presence of protein using Biurets reagent. • Explain your results.

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