Digestion
Overview
Before any enzyme can work on your food, the food has to be broken into small pieces. That mechanical breaking up, by teeth, by the churning stomach and by bile splitting fat into droplets, is physical digestion. It changes the size of the food, not its chemistry, and it sets the stage for the chemical digestion that follows.
In this lesson you will see why chewing matters so much, learn the four kinds of human teeth and the layers inside a tooth, and discover how the stomach and bile each increase the surface area of food. The thread running through it all is one powerful idea: more surface area means faster enzyme action.
Objectives
- [Core] Describe physical digestion as the breakdown of food into smaller pieces without chemical change to the food molecules
- [Core] Describe chemical digestion as the breakdown of large insoluble molecules into small soluble molecules
- [Supplement] State that physical digestion increases the surface area of food for the action of enzymes in chemical digestion
- [Supplement] State the role of chemical digestion in producing small soluble molecules that can be absorbed
- [Supplement] 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
- [Supplement] State where, in the digestive system, amylase, protease and lipase are secreted and where they act
- [Supplement] 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 of proteases in the stomach
Lesson Note
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Lesson Evaluation
Congratulations on completing the lesson on 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.
- Physical digestion is best described as breaking food into smaller pieces: A. by enzymes B. with a chemical change to the molecules C. without a chemical change to the molecules D. into amino acids Answer: C
- A person bites a chunk out of an apple using the flat, chisel-edged teeth at the very front of the mouth. What is the name of these teeth? A. canines B. incisors C. premolars D. molars Answer: B
- The very hard outer layer of the crown of a tooth is the: A. dentine B. enamel C. pulp D. cement Answer: B
- Which part of a tooth contains the nerves and blood vessels? A. enamel B. cement C. pulp D. dentine Answer: C
- The main importance of physical digestion is that it: A. changes food molecules chemically B. increases the surface area of food for enzymes C. absorbs nutrients D. kills bacteria Answer: B
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
Practice Mock Questions
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