M06_REEC5174_09_IE_41_43 - Notes to Instructors Chapter 41...

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Notes to Instructors Chapter 41 Animal Nutrition What is the focus of this activity? Many of the organ systems in mammals are designed to handle the bulk flow of substances into and out of the body. The digestive system is designed to handle the bulk processing and digestion of food. The food we eat is composed of macromolecules—for example, proteins, carbohydrates, and fats that were produced by other organisms. These macromolecules are species-specific. In contrast, the monomers that make up the macromoleules are used almost universally among organisms. The function of digestion is to break food down into its monomers, which can then be taken into the body and used to build our own species-specific macromolecules. As a result, all the processing and digestion of other species’ macromolecules goes on outside of our cells, in the space inside our digestive tract. This space, the lumen of the tract, can therefore be considered a part of the external environment. We have internalized it, or brought it inside of our bodies, to increase the efficiency of food processing and digestion. What is this particular activity designed to do? Activity 41.1 How are form and function related in the digestive system? This activity is designed to help students understand: the basic structure and function of the digestive system in animals, and the roles the various parts of the system play and how these parts are modified to best play these roles. What misconceptions or difficulties can these activities reveal? Activity 41.1 Question 2: If you haven’t encountered it already, you will discover that many students do not understand “how bacteria eat.” They understand that bacteria are decomposers and some are parasites, but in general they don’t know how “eating” occurs. This question is designed to force the point. This question and subsequent questions demonstrate the basic commonalities that exist in methods of digestion across a wide range of organisms, including bacteria, amoebas, and humans. Question 3: The figure reduces the digestive tract to the basics to allow students to see the direct connections between its various parts. For many students this understanding becomes blurred when they view realistic diagrams of the actual organ system. The more linear view presented here helps them see how the system can be understood as a continuous disassembly line. Question 5: Many students don’t understand that the food that enters the digestive tract is technically not inside the body. It is contained in a space that exists within the body. To be in the body requires that a substance cross a cell membrane. Understanding this difference also helps students understand later (Chapter 43) why foreign macromolecules anywhere else in the body produce an immune response. Question 7: Most students understand that enzymes operate using a lock-and-key-type system of recognizing
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This note was uploaded on 02/08/2012 for the course BIOLOGY 101 taught by Professor Hayes during the Spring '09 term at Harvard.

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M06_REEC5174_09_IE_41_43 - Notes to Instructors Chapter 41...

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