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Digestion and Enzymes What Happens the Food we Eat! 5 Stages of Digestion • • • • • • • • • • Ingestion Digestion Absorption Assimilation Egestion • http://www.learning-isfun.co.uk/biology/nutrition.html In Down Around And Eject The Digestive System Oesphagus Stomach Liver Pancreas Large Intestine Small Intestine Appendix The Mouth • Teeth break down food into small pieces • Salivary glands make saliva. • Chewed food gets mixed with saliva • Saliva contains enzymes, which start to digest starch to sugar Teeth Canines • Four types of teeth: Incisors 1. Incisors 2. Canines 3. Pre – Molars 4. Molars Premolar Molar Location of Teeth Canines Pre - Molars Molars Incisors Canines Pre - Molars Molars Biting and Cutting Grasping and Tearing Incisor Canine Grinding and Crushing Pre - Molar Grinding and Crushing Molar The Oesphagus • Passes food down to your stomach • The oesophagus has circular muscles in its wall • These muscles contract and squeeze in behind the food to push it along Oesphagus 25 cm long The Stomach • Muscular bag that holds 2 litres of food • Secretes hydrochloric acid • Makes digestive juices • Muscular walls churn the food making sure it’s all mixed • After 2-3 hours churning it’s a runny liquid The Liver • After food has been absorbed into the blood, the food is taken to the liver • The liver processes some of it, before it goes any further • The food dissolved in plasma is the taken to other parts of the body Pancreas • Leaf – like structure • Produces digestive enzymes e.g. amylase • Passed in Small Intestine and helps in the digestion of food • Helps control blood sugar The Small Intestine • Actually 6 m long! • Plays important roles in digestion and absorption • Two important liquids are added here: Pancreatic juices Bile • 90% of food is digested and absorbed here! The Large Intestine • Shorter but wider than small intestine • Absorbs water from food • Passes water into the blood • Mainly fibre, dead cell, bacteria and water reach here! OB8 – Investigate the action of amylase on starch; identify the substrate, product and enzyme An enzyme is a biological catalyst – speeds up chemical reactions inside cells Without Catalyst With Catalyst Enzymes • Proteins found in every cell of the body • Digestive enzymes – involved in breaking down food – Amylase in Saliva • Amylase breaks starch down into Maltose • http://subscription.echalk. co.uk/index.htm How Enzymes Work Substrate Enzyme Product Amylase Digestion Starch Absorption Glucose Intestinal wall OB8 - Investigate the Action of Amylase on Starch Thermometer Test tube Water 37oC for 10 minutes Beaker Wire Gauze Bunsen Burner Tripod Stand OB8 - Investigate the Action of Amylase on Starch Starch not broken down Starch broken down Tube A Tube B Iodine Starch Soln. + Water Starch Soln. + Amylase To Show that Amylase Breaks Starch into Glucose No Glucose Present Glucose Present Tube D Tube C Benedicts Solution Starch Soln. + Water Starch Soln. + Amylase Test for Glucose Benedicts Solution Positive Negative Test Yourself! Oesphagus 1 2 Stomach Liver 3 Pancreas 4 Large 6 Intestine 5 Small Intestine Appendix 7 Facts for the Curious! • What is added to the food each day as it passes through the gut……. • In mouth: saliva = 1 litre • In stomach: acid & enzymes = 1 litre • In intestines: bile from liver = ¾ litre, pancreatic enxymes = ¾ litre, intestinal enymes = ½ litre • Total: 4 litres!! Facts for the Curious • 70 year olds only produce about half the amount of enzymes that they produced when they were 20! JOBS OF THE DIGESTIVE SYSTEM ORGANS
