Visualizing Nutrition- Chapter 3-1

Visualizing Nutrition- Chapter 3-1 - 54 Digestion: From...

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Unformatted text preview: 54 Digestion: From Meals to Molecules 3 T he human body has been compared to a car: We fill the tank of our car with gasoline to get down the highway; we fill our body with food to get on with life. In both machines, combustion with oxygen releases energy. In a cars engine, the explosion releasing the energy is contained within a cylinder. In a human, the energy is released by reactions within a living cell. Our bodies are machine-like in another way as well: They are virtually identical to one another. Like cars, we look different on the outside but are the same on the inside. The processes that drive uslike the internal combustion engine, no matter where its manufacturedare more similar than different because they are based on the same fundamental chemical reactions. Despite the similarities, however, there are differences between human bodies and machines. An automobile cannot use gasoline to heal itself or to grow, as we do with nutrients. Although a gas tank and a stomach both store fuel, gasoline travels unchanged through the fuel line to the engine, whereas in humans the digestive system must break down the fuel into smaller units before it can be used by the body. Cars are fueled only by gasoline, but the human digestive system must process fuel from many sources for use by the high-performance machine that is the human body. c03.qxd 7/24/09 2:54 PM Page 54 CHAPTER OUTLINE n The Organization of Life p. 56 Veins n The Digestive System p. 60 n Digestion and Absorption of Nutrients p. 62 n Digestion in Health and Disease p. 71 n Delivering Nutrients and Eliminating Wastes p. 76 H2O O2 C O2 C O2 n An Overview of Metabolism p. 80 c03.qxd 7/24/09 2:54 PM Page 55 Process Diagram From atoms to organisms Figure 3.1 atter, be it a meal you are about to eat or the plate you are about to eat it from, is made up of atoms ( Figure 3.1 ) . Atoms combine to form molecules , which can have different properties from those of the atoms they contain. In any living sys- tem, the molecules are orga- nized into cells , the smallest units of life. Cells that are sim- ilar in structure and function form tissues . The human body contains four types of tissue: muscle, nerve, epithe- lial, and connective. These tissues are organized in vary- 56 CHAPTER 3 Digestion: From Meals to Molecules The Organization of Life LEARNING OBJECTIVES Describe the organization of living things, from atoms to organisms. Name the organ systems that work with the digestive system to deliver nutrients and eliminate wastes. M n atoms The smallest units of an element that retain the properties of the element. n cells The basic structural and functional units of living things....
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Visualizing Nutrition- Chapter 3-1 - 54 Digestion: From...

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