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Digestion of Nutrients

Digestion of Nutrients. Step 2:Mechanical breakdown of food. Digestion video ( To be played in Winamp as the file would not insert as a link). Digestive system. FRED (Human digestive system model) ( To be pulled apart & discussed with students) .

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Digestion of Nutrients

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  1. Digestion of Nutrients

  2. Step 2:Mechanical breakdown of food • Digestion video (To be played in Winampas the file would not insert as a link).

  3. Digestive system • FRED (Human digestive system model) • (To be pulled apart & discussed with students).

  4. Mechanical breakdown of food & secretion of enzymes • Where does mechanical breakdown of food begin? • Where does it continue? • What enzyme is secreted in the mouth? Its purpose? • What is the ball of food called that is swallowed? • How does it move down the oesophagus? • What is secreted in the stomach? • What are the components of gastric juice? • What does pepsin/pepsidase do? • What is food called once it mixes with gastric juice? • What organs does the stomach signal to that food is coming? • How does it do this? • What muscle controls the flow of food to the small intestine? What is the 1st section of the small intestine called?

  5. Mechanical breakdown of food & secretion of enzymes • Mechanical breakdown of food begins in the mouth, & amylase (an enzyme) is secreted to begin breakdown of starch to simpler sugars • The bolus (ball of food & saliva) is swallowed, & moves down the oesophagus by peristalsis • Further mechanical breakdown occurs in the stomach, & food is mixed with secreted gastric juice (mucus, pepsin (enzyme), HCl & H20) to make chyme • Pepsidase breaks proteins into peptides (smaller fragments) • The stomach produces hormones that signal the pancreas & gall bladder that food is coming • The pyloric sphincter regulates chymeexiting the stomach to the small intestine

  6. Duodenum, pancreas & gall bladder • What is the 1st section of the intestine called that chyme exits the stomach into? • What does the pancreas secrete into the duodenum? • What does the gall bladder secrete into the duodenum?

  7. Duodenum, pancreas & gall bladder • From the stomach chyme enters the small intestine (duodenum, jejunum, ileum), 1st the duodenum • The gall bladder & pancreas then secrete into the duodenum • Pancreas > bicarbonate neutralises the HCl from the stomach • >amylases break down carbohydrates • >trypsinfurther digests proteins into peptides • >lipases break fats & phospholipids into glycerol & fatty acids • > nucleases break down nucleic acids • Gall bladder > bile: • salts emulsify fats into smaller drops in aqueous solution • the smaller droplets of fat aid digestion by increasing SA:vol ratio • allows lipases (from the pancreas) to break fats down into fatty acids & glycerol

  8. Absorption in the small intestine:Jejunum & Ileum • What now occurs in the small intestine? • What enzymes are still present/working? • > peptides amino acids • > carbohydrates glucose • > lipids fatty acids & glycerol

  9. Absorption in the small intestine:Jejunum & Ileum • What occurs in the small intestine after food has been broken down into its constituent macromolecules? • (Biology, 4th Ed. Campbell) • What features of the small intestine assist absorption? • How do nutrients move through the wall of the small intestine?

  10. Absorption in the small intestine:Jejunum & Ileum • Into where do sugars & amino acids diffuse? • (Biology, 4th Ed. Campbell) • Into where do glycerol & fatty acids diffuse? • How do nutrients move through the wall of the small intestine?

  11. Absorption in the small intestine:Jejunum & Ileum • Food is further broken down into macromolecules that can be absorbed through the wall of the small intestine • The jejunum & ileum have structural features that assist absorption: • > thin wall, allowing diffusion of nutrients • > villi & microvilli greatly increase the surface area for absorption • Glucose & amino acids are absorbed through capillaries lining the microvilli • Glycerol & fatty acids are absorbed through lacteals & into the lymph fluid, which drains out into the bloodstream in the neck

  12. The LARGE intestine: colon & rectum • What moves into the colon? • What happens in the colon? • Fibre? • Bacteria break down 30-40% into fatty acids & glycerol. • Some vitamins (Vitamin K) • Enzymes, H2O, electrolytes? • What action continues to move contents through the gut? • What moves into the rectum? • faeces

  13. The LARGE intestine: colon & rectum • What does faeces contain? • What macromolecular contents are in food that we need? • Is it possible to absorb all of the nutrients in our food? • Sugars/starches completely absorbed • 10% fat remains • 15% protein remains • ~35% fibre gets digested in the colon • Overall ~ 90% energy in food has been absorbed

  14. Digestion in herbivores (adjunct) • What do herbivores eat? • What form is the major form of stored carbohydrate in plants? • Can animals break cellulose down? • Bacteria ferment the cellulose, & herbivores have large expanded sections in their gut to accommodate them • What are the two classifications of herbivores: • foregut fermenters & hindgut fermenters

  15. Obtaining Energy & Nutrients for Life Students to concept map what they have learnt in this unit on the whiteboard! (Otherwise titled: “The crowd goes wild”)

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