Chapter 50 Animal Nutrition

1. Chapter 50Animal Nutrition

2. Chapter 50: Animal Nutrition Nutrient Requirements Adaptations for Feeding Digestion Structure and Function of the Vertebrate Gut

3. Chapter 50: Animal Nutrition Control and Regulation of Digestion Control and Regulation of Fuel Metabolism The Regulation of Food Intake Toxic Compounds in Food

4. Nutrient Requirements • Animals are heterotrophs that derive their energy and structural building blocks from food, therefore ultimately from autotrophs. 4

5. Nutrient Requirements • Carbohydrates, fats, and proteins supply animals with metabolic energy. • A measure of the energy content of food is the calorie. • Excess caloric intake is stored as glycogen and fat. Review Figure 50.2 5

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7. Nutrient Requirements • An animal with insufficient caloric intake is undernourished and must metabolize its stored glycogen, fat, and finally its own protein. • Overnutrition in humans can be a serious health hazard. Review Figure 50.3 7

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9. Nutrient Requirements • For many animals, food provides essential carbon skeletons they cannot synthesize themselves. Review Figure 50.4 9

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11. Nutrient Requirements • Humans require eight essential amino acids. • All are available in milk, eggs, or meat, but not in all vegetables. • Thus, vegetarians must eat a mix of foods. Review Figure 50.5 11

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13. Nutrient Requirements • Different animals need mineral elements in different amounts. • Macronutrients are needed in large amounts. • Micronutrients are needed in small amounts. Review Table 50.1 13

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16. Nutrient Requirements • Vitamins are organic molecules that must be obtained in food. Review Table 50.2 16

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19. Nutrient Requirements • Malnutrition results when any essential nutrient is lacking from the diet. • Lack of any essential nutrient causes a deficiency disease. Review Table 50.2 19

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22. Adaptations for Feeding • Animals can be characterized by how they acquire nutrition • Saprotrophs and detritivores depend on dead organic matter • Filter feeders strain the environment for food • Herbivores eat plants • Carnivores eat animals. 22

23. Adaptations for Feeding • Behavioral and anatomical adaptations reflect feeding types. • In vertebrates, teeth have evolved to match diet. Review Figure 50.9 23

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26. Digestion • Digestion involves the breakdown of complex food molecules into monomers that can be absorbed and utilized by cells. • In most animals, digestion is extracellular, external to the body, occurring in a tubular gut with regions specialized for different digestive functions. Review Figure 50.10 26

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28. Digestion • Absorptive areas of the gut are characterized by a large surface area. Review Figure 50.11 28

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31. Digestion • Hydrolytic enzymes break down proteins, carbohydrates, and fats into their monomeric units. • To prevent the organism itself from being digested, these are released as inactive zymogens, only activated when secreted into the gut. 31

32. Structure and Function of the Vertebrate Gut • Cells and tissues of the vertebrate gut are organized in the same way throughout its length. • The innermost tissue layer, the mucosa, is the secretory and digestive surface. • The submucosa contains secretory cells and glands, blood and lymph vessels, and nerves. • External to the submucosa are two smooth muscle layers that move food through the gut. • Between these is a nerve network that controls gut movements. Review Figure 50.13 32

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34. Structure and Function of the Vertebrate Gut • The swallowing reflex pushes food into the esophagus. • Waves of smooth muscle contraction and relaxation (peristalsis) move food from the beginning of the esophagus through the length of the gut. • Sphincters block the gut at certain locations, but relax as a wave of peristalsis approaches. Review Figure 50.14 34

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37. Structure and Function of the Vertebrate Gut • Enzymatic digestion begins in the mouth, where amylase is secreted with saliva. • Protein digestion begins in the stomach with pepsin and HCl secreted by the stomach mucosa. • The mucosa also secretes mucus, to protect gut tissues. Review Figure 50.15 37

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40. Structure and Function of the Vertebrate Gut • In the the duodenum, pancreatic enzymes carry out most of digestion. • Bile from liver and gallbladder assists in digestion of fats, breaking them into micelles. • Bicarbonate ions from the pancreas neutralize the pH of the chyme entering from the stomach to produce an environment conducive to pancreatic enzyme action. Review Figure 50.16, Table 50.3 40

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43. Structure and Function of the Vertebrate Gut • Final enzymatic cleavage of peptides and disaccharides occurs on the cell surfaces of the intestinal mucosa. • Amino acids, monosaccharides, and many inorganic ions are absorbed by the microvilli of the mucosal cells. • Often specific carrier proteins in the membranes of these cells transport nutrients into the cells. • Sodium cotransport is a common mechanism for actively absorbing nutrient molecules and ions. 43

44. Structure and Function of the Vertebrate Gut • Fats are absorbed mostly as monoglycerides and fatty acids, the product of lipase action on triglycerides in food. • These products pass through mucosal cell membranes and are resynthesized into triglycerides within the cells. • The triglycerides are combined with cholesterol and coated with protein to form chylomicrons, which pass out of mucosal cells into lymphatic vessels in the submucosa. Review Figure 50.17 44

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46. Structure and Function of the Vertebrate Gut • Water and ions are absorbed in the large intestine so that waste matter is consolidated into feces. 46

47. Structure and Function of the Vertebrate Gut • In herbivores such as rabbits and ruminants, some compartments of the gut have populations of microorganisms that aid in digesting molecules otherwise indigestible. Review Figure 50.18 47

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49. Control and Regulation of Digestion • Digestion processes are coordinated and controlled by neural and hormonal mechanisms. • Salivation and swallowing are autonomic reflexes. • Stomach and small intestine actions are largely controlled by the hormones gastrin, secretin, and cholecystokinin. Review Figure 50.19 49

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