Chemical Digestion
Overview
The bread, meat and oil on your plate are made of giant molecules that are too big and too insoluble to cross the gut wall. Chemical digestion is the work of enzymes that cut these giants into small soluble molecules: starch into sugars, protein into amino acids, fat into fatty acids and glycerol, so they can be absorbed into your blood.
In this lesson you will learn what each digestive enzyme does, where it is made and where it acts, and the special job of stomach acid. Extended students will follow starch and protein through their exact two-step breakdown and see why bile must neutralise the acid leaving the stomach.
Objectives
- Describe chemical digestion as the breakdown 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
- [Supplement] 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
- [Supplement] 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
- [Supplement] 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
Lesson Note
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Lesson Evaluation
Congratulations on completing the lesson on Chemical Digestion. Now that youve explored the key concepts and ideas, its time to put your knowledge to the test. This section offers a variety of practice questions designed to reinforce your understanding and help you gauge your grasp of the material.
You will encounter a mix of question types, including multiple-choice questions, short answer questions, and essay questions. Each question is thoughtfully crafted to assess different aspects of your knowledge and critical thinking skills.
Use this evaluation section as an opportunity to reinforce your understanding of the topic and to identify any areas where you may need additional study. Don't be discouraged by any challenges you encounter; instead, view them as opportunities for growth and improvement.
- Which enzyme breaks down protein to amino acids? A. amylase B. lipase C. protease D. maltase Answer: C
- The products of fat digestion by lipase are: A. glucose and maltose B. amino acids C. fatty acids and glycerol D. simple sugars only Answer: C
- One function of hydrochloric acid in the stomach is to: A. digest protein directly B. provide an acidic optimum pH for protease C. emulsify fats D. neutralise acid Answer: B
- [Supplement] Maltose is broken down to glucose by the enzyme: A. amylase B. pepsin C. maltase D. lipase Answer: C
- [Supplement] Pepsin works best in conditions that are: A. alkaline B. neutral C. acidic D. boiling Answer: C
Available on the Green Bridge App
Download the Green Bridge CBT app on your phone or computer to access full lesson notes, practice questions, and more.
Available on the Green Bridge App
Download the Green Bridge CBT app on your phone or computer to access full lesson notes, practice questions, and more.
Recommended Books
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