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Chapter 2 Digestion

Chapter 2 Digestion. (Higher Level only ). (Higher Level only ). Digestion Digestive enzymes Alimentary canal Peristalsis Chyme Faeces Nutrient absorption. 2. (Higher Level only ).

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Chapter 2 Digestion

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  1. Chapter 2 Digestion (Higher Level only)

  2. (Higher Level only) Digestion Digestive enzymes Alimentary canal Peristalsis Chyme Faeces Nutrient absorption 2

  3. (Higher Level only) Understand why we need food and be able to list the factors that influence our food choices Have a good understanding of each of the six nutrients in terms of their composition, classification, sources, functions in the body and their RDA Understand and be able to describe the effects of over-consumption of certain nutrients on the body - fat, sugar and vitamin/mineral supplements Know the nutrition related causes of the following deficiency diseases and be able to describe their symptoms - constipation and bowel disease, scurvy, rickets, neural tube defects, tooth decay, osteomalacia and osteoporosis, anaemia and goitre. Understand the term energy balance be able to describe how it can be maintained by the individual. Understand the terms physical digestion and chemical digestion. Understand what a digestive enzyme is. Be able to explain what protein, fats and carbohydrates are broken down into during digestion. Be able to list and locate the areas of the alimentary canal on a diagram. Be able to describe the passage of food through the alimentary canal from mouth to rectum. Be able to describe how digested nutrients are absorbed and transported to body cells from the small intestine. 3

  4. (Higher Level only) • Protein, fat and carbohydrate must be digested or broken down before they can be used by the body. • Minerals, vitamins and water, on the other hand, need no digestion and can be used by the body as they are. • Food is physically broken down by being chewed in the mouth and churned around in the stomach (forming chyme). • Protein, fat and carbohydrate are chemically broken down by enzymes. • Digestive enzymesare chemical substances that break down food. Enzymes themselves do not change in the process. • Each enzyme can only work on one nutrient. For example, an enzyme that can break down fats would have no effect on protein. 4 Essentials for Living, 3rd Edition

  5. (Higher Level only) Digestion of protein Digestion of fat Digestion of carbohydrate 5 Essentials for Living, 3rd Edition

  6. (Higher Level only) The alimentary canal 1. Digestion takes place in the alimentary canal. • 1 Mouth • 2 Oesophagus • 3 Stomach • 4 Small intestine • 5 Pancreas • 6 Liver • 7 Large intestine • 8 Rectum 6 Essentials for Living, 3rd Edition

  7. (Higher Level only) 2. The process of digestion in the mouth and oesophagus The teeth physically break food down in the mouth. The tongue mixes it with saliva from the salivary glands. Saliva contains the enzyme amylase. Amylase breaks down long chains of cooked starch, such as bread, into shorter chains called maltose. Food is then swallowed and passes into a long tube called the oesophagus. The walls of the oesophagus move in and out, squeezing the food along. This is called peristalsis. 7 Essentials for Living, 3rd Edition

  8. (Higher Level only) 3. The process of digestion in the stomach • Food then passes into the stomach. The stomach can be described as a muscular bag in the left-hand side of the abdomen under the diaphragm. • Food is churned about in the stomach until it turns into a liquid called chyme. The walls of the stomach produce a juice called gastric juice. This juice is made of a strong acid, hydrochloric acid, and two enzymes. • One of these enzymes is called pepsin. It starts to digest protein by breaking the long amino acid chains into shorter ones called peptides. 8 Essentials for Living, 3rd Edition

  9. (Higher Level only) 4. The process of digestion in the small intestine Next, food passes into the narrow, but very long, small intestine. Again, peristalsis keeps the food moving along. Three digestive juices work here to complete the digestion of our food: Pancreatic juice (made by the pancreas) Bile (made by the liver and stored in the gall bladder; works on fats) Intestinal juice (made by the intestine itself) • All three juices work together to change: • Protein and peptides to free amino acids • Carbohydrates to monomers (simple sugars) • Fats to fatty acids and glycerol • Digested nutrients are then absorbed into the blood. They travel to our body cells, where they carry out their various functions, e.g. producing heat and energy. 9 Essentials for Living, 3rd Edition

  10. (Higher Level only) 5. The process of absorptionin the large intestine Waste that is not absorbed now passes into the large intestine (colon or bowel). As it passes into the large intestine, the waste is still very liquid. Some of this water passes back through the walls of the intestine into the bloodstream. This causes the waste to become more solid. It is now called faeces. Faeces passes out of the body through the rectum and anus. 10 Essentials for Living, 3rd Edition

  11. (Higher Level only) Absorption of nutrients from the small intestine The walls of the small intestine resemble a very fine carpet: they are covered in a huge number of hair-like projections called villi. Each villus has a tiny blood vessel and a lymph vessel. Digested nutrients pass into these vessels. • The absorption and transport of protein and carbohydrate is simple: • small intestine  blood vessel of villi  bloodstream  body cells • Fats are more complicated: • small intestine  lymph vessel of villi  lymph system  bloodstream  body cells 11 Essentials for Living, 3rd Edition

  12. (Higher Level only) Digestion video link Watch the GCSE Science Revision – Digestion clip uploaded by JamJarMMX on YouTube:   https://www.youtube.com/watch?v=32gNePkj1_4 12 Essentials for Living, 3rd Edition

  13. (Higher Level only) Name the parts of the alimentary canal. How is food physically broken down? How is food chemically broken down? What are digestive enzymes? What is their function? What is the movement of the wall of the alimentary canal called? Describe the process of digestion in the stomach. What is chyme? What are proteins broken down into during digestion? What are carbohydrates broken down into during digestion? 13 Essentials for Living, 3rd Edition

  14. (Higher Level only) What are fats broken down into during digestion? Name one enzyme found in the stomach. What nutrient does it work on? Name the three digestive juices present in the small intestine. Give another name for the large intestine. What is the main function of the large intestine? What is the name given to solid waste? What are the hair-like projections that line the small intestine called? Describe the absorption of protein and carbohydrate from the small intestine. Describe the absorption of fat from the small intestine. 14 Essentials for Living, 3rd Edition

  15. (Higher Level only) Assignment 7 Now test yourself at www.eTest.ie. 15 Essentials for Living, 3rd Edition

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