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🎓 IGCSE Biology - The Complete Course: https://www.tes.com/teaching-resource/resource-12989155 IGCSE Chemistry - The Complete Course: 🎓 Complete Teaching Resource (including past exam questions and mark schemes organised by chapter): https://www.tes.com/teaching-resource/resource-13280954 🎓 Student resource (PDF only): https://www.tes.com/teaching-resource/resource-13245244 🎓 All the videos (the complete library on Patreon): https://www.patreon.com/igbiocomplete ☕️ Buy me a coffee - https://www.buymeacoffee.com/ArthurJohnParker Cambridge IGCSE Biology (0610/0970) Chapter 7 - Human nutrition Topic 7.4 - Chemical digestion For exams from 2025 (core and extended) As always this video follows the Cambridge syllabus exactly and contains absolutely everything you need to know for your final exam! My other channels: @igpecomplete - Cambridge IGCSE PE @ocrpecomplete - OCR GCSE PE Timestamps: 0:00 Contents 0:39 Chemical digestion 1:18 Amylase 1:48 Proteases 2:32 Lipase 2:44 Chemical digestion of starch (extended) 3:14 Chemical digestion of proteins (extended) 3:49 Bile Core content: - Describe chemical digestion as the break down of large insoluble molecules into small soluble molecules. - State the role of chemical digestion in producing small soluble molecules that can be absorbed. - Describe the functions of enzymes as follows: (a) amylase breaks down starch to simple reducing sugars (b) proteases break down protein to amino acids (c) lipase breaks down fats and oils to fatty acids and glycerol - State where, in the digestive system, amylase, protease and lipase are secreted and where they act. - Describe the functions of hydrochloric acid in gastric juice, limited to killing harmful microorganisms in food and providing an acidic pH for optimum enzyme activity. Extended content: - Describe the digestion of starch in the digestive system: (a) amylase breaks down starch to maltose (b) maltase breaks down maltose to glucose on the membranes of the epithelium lining the small intestine - Describe the digestion of protein by proteases in the digestive system: (a) pepsin breaks down protein in the acidic conditions of the stomach (b) trypsin breaks down protein in the alkaline conditions of the small intestine - Explain that bile is an alkaline mixture that neutralises the acidic mixture of food and gastric juices entering the duodenum from the stomach, to provide a suitable pH for enzyme action.
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