The Need for Food

1. The Need for Food Animal Survival Standard Grade Biology

2. Learning Outcome 1 • Explain in simple terms why food is required by animals.

3. Learning Outcome 2 • State the chemical elements present in carbohydrates, fats and proteins • Describe the simple structure of carbohydrates, proteins and fats in terms of simple sugars, amino acids, fatty acids and glycerol.

4. You are what you eat!! • In this lesson you will • Look at what is a balanced diet • Carry out food tests on • Starch • Glucose • Protein • Fat • Discuss what happens if you don’t eat a balanced diet

5. Balanced Diet

6. What is a balanced diet? • Your diet must include five groups of food substances • Carbohydrates, fats, proteins, minerals and vitamins • It must also include water and fibre. • A balanced diet is a diet that provides enough of these substances in the correct proportions to keep you healthy.

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

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

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

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

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

12. 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.

13. 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.

14. What happens if you don’t eat a balanced diet. What is this cartoon trying to demonstrate? Can you think of any examples of health problems that arise from not eating a balances diet? Give three examples and explain the effects on health.

15. Learning Outcomes 3 • State that digestion is the breakdown of large particles of food into smaller particles to allow absorption into the blood stream through the small intestine wall. • Explain that digestion involves the breakdown of insoluble food substances into soluble food substances

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

17. The gut as a production line

18. Learning Outcome 4 • identify in a diagram / model the main parts of the mammalian alimentary canal and associated organs (mouth, salivary glands, oesophagus, stomach, pancreas, liver, gall bladder, small intestine, large intestine, appendix, rectum and anus) • state the sites of production of the main digestive juices in mammals (salivary glands, stomach, pancreas, liver, small intestine)

19. 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.

20. 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.

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

22. Mammalian teeth The Need for food Animal Survival SG Biology

23. Learning Outcomes (5) • To know the different structure and functions of each type of tooth • To understand the adaptations of a herbivore, omnivore and a carnivore to feeding.

24. Feeding in mammals • Mammals have teeth which may be used to bite pieces of food and to chew it into smaller pieces before swallowing. • The shapes of teeth are suited to their function. • Incisors and canines are used for biting • Premolars and molars are used for chewing and crushing food.

25. Patterns of Teeth

26. Human Jaw

27. teeth • There are different types of teeth, each specially shaped to perform a particular job. • Incisor - A broad flat sharp tooth found at the front of the mouth. Designed for biting and cutting food. • Canine - A sharp pointed tooth for piercing flesh and tearing. • Pre-molar & molar - A broad flat tooth with many cusps. Its rough surface is used for crushing, grinding and chewing food

28. Carnivore adaptations • Look at the dog skull, and the diagrams of a dogs skull. • With the aid of a diagram – make notes explaining how the dogs teeth and jaws are adapted for a carnivorous diet.

30. Herbivore adaptations • Look at the sheep’s skull, and the diagrams of a sheep skull. • With the aid of a diagram – make notes explaining how the sheep's teeth and jaws are adapted for a herbivorous diet.

32. Learning Outcome 6 • Explain the mechanism of peristalsis • Explain how the contractions of the stomach help in the chemical breakdown of food.

33. 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.

34. 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

35. Peristalsis in the gullet

36. Learning Outcome 7 • State that different enzymes are responsible for the breakdown of carbohydrates, proteins and fats. • Give an example of an amylase, a protease and a lipase. State their substrates and products.

37. Digestion of Starch • Take 2ml of 1% starch solution • Test for starch • Test for sugars • Take 2 ml 1% starch solution, add 2ml 2% amylase solution • Leave for 20 minutes • Test for starch • Test for sugar

38. Action of amylase on starch • Put two drops of iodine solution into all the wells on a white spotting tile • Add 2ml 1% starch solution and 2ml 2% amylase solution to a test tube. • Every minute, test the contents of the test tube for starch. • Write a conclusion on your results

39. 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 (as well as killing bacteria in food)

40. 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 0.5 ml water • Add 0.5 ml trypsin • Add 0.5ml trypsin

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

42. Fat Digestion • Milk does not dissolve in water, in the digestive system, bile produce by the liver (stored in the gall bladder) emulsifies fats to give a larger surface area for enzymes to work on. • You are going to use phenolphthalein to investigate the effect of bile on the digestion of fat.

43. Fat Digestion • Take 4 test tubes and number them 1, 2, 3 and 4. • set up the test tubes as shown in the table below.

44. Fat Digestion • Add 5 drops of phenolphthalein to each test tube • Add sodium carbonate to each test tube until the solution goes pink. • Add 0.5ml of lipase to test tubes 1, 2 and 3. • Add 0.5 ml water to test tubes 4. • Observe your results. Try to explain what you are observing.

45. Chemical Digestion • Enzymes • 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 – 40o) • Work best at an optimum pH

46. 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 (carbohydrase enzyme) into maltose (sugar) • Maltose is then broken down by maltase to form glucose

47. Chemical Digestion • There are also other substances in the digestive system which help with the breakdown of food. • Hydrochloric acid • Secreted by stomach • Kills the bacteria in food • Enzymes in stomach work best at a low pH e.g. pepsin

48. 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)

49. Learning Outcome 8 • State that only small soluble molecules can pass through the wall of the small intestine. • Explain how the structure of the small intestine is related to its function. • Explain how the structure of a villus, including the lacteal and the blood capillaries, are related to the absorption and transport of food. • Describe the role of the large intestine in water absorption and elimination.

50. Digestion in the small intestine • 3 important liquids are added to the food • Pancreatic juice (carbohydrases, proteases and lipases) • Bile (neutralises acid and emulsifies fat) • Intestinal juice (carbohydrases, proteases and lipases)