1. Digestion Textbook B Chp 11

2. Topics Overview of Digestion Parts & Functions of Alimentary Canal Enzymes Food Tests

4. Overview Big Idea: what happens when (& after) we eat food? Why do we need to eat food in the first place? – For Energy – For growth – For maintenance (to remain healthy)

5. Processes of Eating 1.Ingestion 2.Digestion 3.Absorption 4.Assimilation 5.Egestion

6. ALIMENTARY CANAL

7. Parts of the Digestive System 1.Mouth 2.Oesophagus 3.Stomach 4.Small Intestine 5.Large Intestine 6.Liver, Pancreas, Gall Bladder 7.Rectum, Anus

8. Alimentary Canal

9. Video Once Upon a Time…Life (Part 1) https://www.youtube.com/watch?v=M- 1PuS2NVOw https://www.youtube.com/watch?v=M- 1PuS2NVOw Once Upon a Time…Life (Part 2) https://www.youtube.com/watch?v=M4e6qf8r 8Tk https://www.youtube.com/watch?v=M4e6qf8r 8Tk Once Upon a Time…Life (Part 3) https://www.youtube.com/watch?v=QY5q4GJ OOgg https://www.youtube.com/watch?v=QY5q4GJ OOgg

10. Mouth Chewing breaks up food into smaller pieces – Increase surface area for digestion Saliva softens & moistens food (aid digestion) Saliva contains the enzyme amylase – Amylase converts starch to maltose

11. Oesophagus Carry food from mouth to stomach through the process peristalsis

12. Stomach Many layers of muscle surround the stomach walls – mixes food by contraction and relaxation of muscles Contains hydrochloric acid (pH 1-2) – kills bacteria – provides an acidic environment for enzymes (proteases) to work Proteases convert protein to amino acids

13. Small Intestines The small intestines are made up of three parts: duodenum, jejunum and ileum Duodenum – contains several types of enzymes to digest food – amylase convert starch to maltose – lipase convert fat to fatty acid & glycerol – protease convert protein into amino acids

14. Small Intestines While food is in the duodenum, different substances from other organs are also released into the duodenum to aid digestion – Bile Produced from Liver, stored in Gall Bladder, and released to duodenum through the Bile duct Bile emulsifies fat, making fat globules smaller and increasing surface area – Pancreatic juice released from Pancreas Amylase, protease and lipase

15. Small Intestines The small intestines are very long so that there is large surface area to absorb digested food The surface area is increased further by the presence of villi, finger- like structures Greater surface area allow for faster absorption of digested food

16. Other Parts Large Intestine (colon) absorbs water and mineral salts Rectum stores undigested remains of food (faeces) Anus, where faeces is expelled from the body Did you know: colonoscopy

17. Physical vs Chemical Processes Throughout digestion, there is a combination of physical and chemical processes Physical processes involve breaking food down into smaller parts, but does not change the nature of the food (e.g. chewing, churning, emulsification) Chemical processes involve breaking food down into different chemical components (e.g. work by enzymes)

18. ENZYMES

19. Enzymes Recall: what is a chemical reaction? An enzyme is a catalyst, something which speeds up chemical reactions (but is not “used up” in the process; remains unchanged) The “raw material” which an enzyme works on is called the substrate, the “end product” is called the product Enzymes are made of proteins Enzyme activity is affected by temperature as well as pH (acidity)

20. Enzymes & Temperature Recall in particulate model, we studied that at higher temperatures, molecules move faster Enzymes and substrates collide with each other more frequently when temperature is raised, increasing rate of reaction However, if the temperature becomes too high, the enzyme becomes denatured (i.e. changed in shape, become useless) Optimum temperature around 40 °C

21. Enzymes & pH pH is a measure of acidity Neutral is pH7, less than 7 is acidic, more than 7 is alkali (or basic) Stomach has around pH 1-2 (very acidic) due to the presence of hydrochloric acid produced by gastric juices Enzymes have an optimum pH, depends on type of enzyme (stomach protease pH 2, salivary amalyse at pH 8, pancreatic lipase at pH 11)

22. Enzyme Summary EnzymeLocationSubstrateProduct AmalyseMouth (from Salivary Glands) & Duodenum (from Pancreas) StarchMaltose ProteaseStomach, Duodenum (from Pancreas) ProteinAmino Acids LipaseDuodenum (from Pancreas) FatFatty Acid + Glycerol

23. FOOD TESTS

24. Food Tests There are 4 food tests you need to perform for your lab. These tests check if there are certain nutrients present in the sample. 1.Benedict’s test (for reducing sugars) 2.Iodine Test (for starch) 3.Emulsion Test (for fat/oil) 4.Biuret Test (for protein)

25. Food Test Summary NutrientTest NameNutrient Present Nutrient Absent StarchIodine TestBlue-BlackRemains Brown Glucose/Malto se Benedict’s TestRed-Orange Precipitate Remains Blue ProteinBiuret TestViolet SolutionRemains Blue Fat/OilEthanol Emulsion White Emulsion Remains Colourless

26. Summary Overview of Digestion Parts of Alimentary Canal Enzymes Food Test