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Chapter 41: Animal Nutrition 1. Why do we eat? - Fuel (chemical energy) - To get organic material for biosynthesis (carbon skeletons) - Essential nutrients (substances that can’t be made from scratch) 2. What are the 4 main feeding mechanisms of animals? - Suspension feeders - Substrate feeder - Fluid feeders - Bulk feeders Figure 41.2 Four Main Feeding Mechanisms of Animals SUSPENSION FEEDERS SUBSTRATE FEEDERS Feces Baleen Caterpillar FLUID FEEDERS BULK FEEDERS Chapter 41: Animal Nutrition 1. Why do we eat? 2. What are the 4 main feeding mechanisms of feeding? 3. When our bodies need energy, what is the order of fuel usage? 3rd 1st ) (fat- 2nd proteincarbs4. How is appetite regulated in the body? - Hormones source fcn - PYY S. intestine suppresses appetite (after meals) - Insulin pancreas suppresses appetite ↑blood sugar=↑insulin - Ghrelin stomach triggers hunger ↓weight = ↑ghrelin (+) makes dieting difficult - Leptin adipose suppresses appetite - ↑ Fat = ↑ leptin = ↓ appetite - ↓ Fat = ↓ leptin = ↑ appetite Figure 41.5 A few of the appetite-regulating hormones Secreted by the stomach wall, ghrelin is one of the signals that triggers feelings of hunger as mealtimes approach. In dieters who lose weight, ghrelin levels increase, which may be one reason it’s so hard to stay on a diet. Produced by adipose (fat) tissue, leptin suppresses appetite as its level increases. When body fat decreases, leptin levels fall, and appetite increases. Ghrelin Insulin The hormone PYY, secreted by the small intestine after meals, acts as an appetite suppressant that counters the appetite stimulant ghrelin. Leptin PYY A rise in blood sugar level after a meal stimulates the pancreas to secrete insulin (see Figure 41.3). In addition to its other functions, insulin suppresses appetite by acting on the brain. Chapter 41: Animal Nutrition 1. Why do we eat? 2. What are the 4 main feeding mechanisms of feeding? 3. When our bodies need energy, what is the order of fuel usage? 3rd 1st ) (fat- 2nd proteincarbs4. How is appetite regulated in the body? - Hormones source fcn - PYY S. intestine suppresses appetite (after meals) - Insulin pancreas suppresses appetite ↑blood sugar=↑insulin - Ghrelin stomach triggers hunger ↓weight = ↑ghrelin makes dieting difficult - Leptin adipose suppresses appetite - ↑ Fat = ↑ leptin = ↓ appetite - ↓ Fat = ↓ leptin = ↑ appetite 5. What happens if there is a mutation in the leptin system? Figure 41.6 A ravenous rodent Chapter 41: Animal Nutrition 1. 2. 3. 4. 5. 6. Why do we eat? What are the 4 main feeding mechanisms of feeding? When our bodies need energy, what is the order of fuel usage? How is appetite regulated in the body? What happens if there is a mutation in the leptin system? What are essential nutrients & what are the 4 classes? - Nutrients our bodies cannot make - Essential amino acids (8) - Essential fatty acids – certain unsaturated FAs – linoleic acid - Vitamins - Minerals Figure 41.10 Essential amino acids from a vegetarian diet Essential amino acids for adults Methionine Valine Threonine Phenylalanine Corn (maize) and other grains Leucine Isoleucine Tryptophan Lysine Beans and other legumes Table 41.1 Vitamin Requirements of Humans Table 41.2 Mineral Requirements of Humans Chapter 41: Animal Nutrition 1. 2. 3. 4. 5. 6. Why do we eat? What are the 4 main feeding mechanisms of feeding? When our bodies need energy, what is the order of fuel usage? How is appetite regulated in the body? What happens if there is a mutation in the leptin system? What are essential nutrients & what are the 4 classes? - Nutrients our bodies cannot make - Essential amino acids (8) - Essential fatty acids – certain unsaturated FAs – linoleic acid - Vitamins - Minerals 7. What is the difference between malnourished & undernourished? - Under – get all essentials…just not enough - Mal – missing some essentials 8. How is food processed? Figure 41.12 The four stages of food processing Small molecules Pieces of food Mechanical digestion Chemical digestion (enzymatic hydrolysis) Nutrient molecules enter body cells Undigested material Food 1 INGESTION 2 DIGESTION 3 ABSORPTION 4 ELIMINATION Chapter 41: Animal Nutrition 1. 2. 3. 4. 5. 6. 7. 8. 9. Why do we eat? What are the 4 main feeding mechanisms of feeding? When our bodies need energy, what is the order of fuel usage? How is appetite regulated in the body? What happens if there is a mutation in the leptin system? What are essential nutrient & what are the 4 classes? What is the difference between malnourished & undernourished? How is food processed? What is the path that food takes through us? Mouthesophagusstomachsmall intestinelarge intestinerectumtoilet Figure 41.15 The human digestive system Salivary glands Oral cavity Parotid gland Sublingual gland Esophagus Pyloric sphincte r Liver Ascending portion of large intestine Mouth Pharynx Esophagus Submandibular gland Stomach Gallbladder Gallbladder Liver Pancreas Small intestine Large intestine Rectum Appendix Stomach Small intestines Pancreas IIeum of small intestine Cecum Salivary glands Cardiac orifice Tongue Anus Duodenum of small intestine Large intestines Rectum Anus A schematic diagram of the human digestive system Chapter 41: Animal Nutrition 1. 2. 3. 4. 5. 6. 7. 8. 9. Why do we eat? What are the 4 main feeding mechanisms of feeding? When our bodies need energy, what is the order of fuel usage? How is appetite regulated in the body? What happens if there is a mutation in the leptin system? What are essential nutrient & what are the 4 classes? What is the difference between malnourished & undernourished? How is food processed? What is the path that food takes through us? Mouthesophagusstomachsmall intestinelarge intestinerectumtoilet 10. Let’s find out what happens along the way? Figure 41.16 From mouth to stomach: the swallowing reflex and esophageal peristalsis (layer 1) Bolus of food Tongue Epiglottis up Pharynx Glottis Larynx Trachea To lungs Esophageal sphincter contracted Esophagus To stomach Figure 41.16 From mouth to stomach: the swallowing reflex and esophageal peristalsis (layer 2) Bolus of food Tongue Epiglottis up Pharynx Glottis Larynx Trachea To lungs Esophageal Epiglottis sphincter down contracted Esophagus To stomach Glottis up and closed Esophageal sphincter relaxed Figure 41.16 From mouth to stomach: the swallowing reflex and esophageal peristalsis (layer 3) Epiglottis up Bolus of food Tongue Glottis down and open Epiglottis up Pharynx Glottis Larynx Trachea To lungs Esophageal Epiglottis sphincter down contracted Esophageal sphincter relaxed Esophageal sphincter contracted Esophagus To stomach Glottis up and closed Relaxed muscles Contracted muscles Relaxed muscles Figure 41.21 Flowchart of enzymatic digestion in the human digestive system Protein digestion Carbohydrate digestion Nucleic acid digestion Fat digestion Oral cavity, Polysaccharides Disaccharides pharynx, (starch, glycogen) (sucrose, lactose) esophagus Salivary amylase Smaller polysaccharides, maltose Stomach Proteins Pepsin Small polypeptides Lumen of small intestine Polysaccharides Pancreatic amylases Maltose and other disaccharides Polypeptides Pancreatic trypsin and chymotrypsin (These proteases cleave bonds adjacent to certain amino acids.) Smaller polypeptides DNA, RNA Pancreatic nucleases Nucleotides Disaccharidases Dipeptidases, carboxypeptidase, and aminopeptidase (These proteases split off one amino acid at a time, working from opposite ends of a polypeptide.) Monosaccharides Amino acids bile salts prevents small droplets from coalescing into larger globules, increasing exposure to lipase.) Pancreatic lipase Amino acids Small peptides Bile salts Fat droplets (A coating of Pancreatic carboxypeptidase Epithelium of small intestine (brush border) Fat globules (Insoluble in water, fats aggregate as globules.) Glycerol, fatty acids, glycerides Nucleotidases Nucleosides Nucleosidases and phosphatases Nitrogenous bases, sugars, phosphates Figure 41.17 The stomach and its secretions Esophagus Cardiac orifice 5 µm Stomach Interior surface of stomach. The interior surface of the stomach wall is highly folded and dotted with pits leading into tubular gastric glands. Gastric gland. The gastric glands have three types of cells that secrete different components of the gastric juice: mucus cells, chief cells, and parietal cells. Pyloric sphincter Small intestine Folds of epithelial tissue Epithelium 3 Pepsinogen 2 HCl Pepsin (active enzyme) 1 Pepsinogen and HCI are secreted into the lumen of the stomach. 1 2 HCl converts pepsinogen to pepsin. Mucus cells secrete mucus, which lubricates and protects the cells lining the stomach. Chief cells secrete pepsinogen, an inactive form of the digestive enzyme pepsin. Parietal cell Parietal cells secrete hydrochloric acid (HCl). Chief cell - stomach epithelium secretes gastric juice - parietal cells secrete HCl & chief cells secrete pepsinogen - pH = 2 3 Pepsin then activates more pepsinogen, starting a chain reaction. Pepsin begins the chemical digestion of proteins. Figure 41.19 The duodenum Liver Bile Gallbladder Stomach Acid chyme Intestinal juice Pancreatic juice Pancreas Duodenum of small intestine Figure 41.21 Flowchart of enzymatic digestion in the human digestive system Protein digestion Carbohydrate digestion Nucleic acid digestion Fat digestion Oral cavity, Polysaccharides Disaccharides pharynx, (starch, glycogen) (sucrose, lactose) esophagus Salivary amylase Smaller polysaccharides, maltose Stomach Proteins Pepsin Small polypeptides Lumen of small intestine Polysaccharides Pancreatic amylases Maltose and other disaccharides Polypeptides Pancreatic trypsin and chymotrypsin (These proteases cleave bonds adjacent to certain amino acids.) Smaller polypeptides DNA, RNA Pancreatic nucleases Nucleotides Disaccharidases Dipeptidases, carboxypeptidase, and aminopeptidase (These proteases split off one amino acid at a time, working from opposite ends of a polypeptide.) Monosaccharides Amino acids bile salts prevents small droplets from coalescing into larger globules, increasing exposure to lipase.) Pancreatic lipase Amino acids Small peptides Bile salts Fat droplets (A coating of Pancreatic carboxypeptidase Epithelium of small intestine (brush border) Fat globules (Insoluble in water, fats aggregate as globules.) Glycerol, fatty acids, glycerides Nucleotidases Nucleosides Nucleosidases and phosphatases Nitrogenous bases, sugars, phosphates Figure 41.20 Protease activation Pancreas Membrane-bound enteropeptidase Inactive trypsinogen Other inactive proteases Lumen of duodenum Trypsin Active proteases Chapter 41: Animal Nutrition 1. Why do we eat? 2. What are the 4 main feeding mechanisms of feeding? 3. When our bodies need energy, what is the order of fuel usage? 4. How is appetite regulated in the body? 5. What happens if there is a mutation in the leptin system? 6. What are essential nutrient & what are the 4 classes? 7. What is the difference between malnourished & undernourished? 8. How is food processed? 9. What is the path that food takes through us? 10. Let’s find out what happens along the way? 11. What hormones control digestion? - CCK – cholecystokinin - Secretin - Gastrin - Enterogastrone Figure 41.22 Hormonal control of digestion Enterogastrone secreted by the duodenum inhibits peristalsis and acid secretion by the stomach, thereby slowing digestion when acid chyme rich in fats enters the duodenum. Liver Enterogastrone Gallbladder CCK Amino acids or fatty acids in the duodenum trigger the release of cholecystokinin (CCK), which stimulates the release of digestive enzymes from the pancreas and bile from the gallbladder. Gastrin Stomach Pancreas Gastrin from the stomach recirculates via the bloodstream back to the stomach, where it stimulates the production of gastric juices. Secretin Duodenum CCK Key Stimulation Inhibition This ensures enzymes are only present when needed. Secreted by the duodenum, secretin stimulates the pancreas to release sodium bicarbonate, which neutralizes acid chyme from the stomach. Chapter 41: Animal Nutrition 1. Why do we eat? 2. What are the 4 main feeding mechanisms of feeding? 3. When our bodies need energy, what is the order of fuel usage? 4. How is appetite regulated in the body? 5. What happens if there is a mutation in the leptin system? 6. What are essential nutrient & what are the 4 classes? 7. What is the difference between malnourished & undernourished? 8. How is food processed? 9. What is the path that food takes through us? 10. Let’s find out what happens along the way? 11. What hormones control digestion? 12. How & where are nutrients absorbed? - Facilitated diffusion & active transport of monomers - Microvilli of small intestine Figure 41.23 The structure of the small intestine Microvilli (brush border) Vein carrying blood to hepatic portal vessel Blood capillaries Epithelial cells Muscle layers Villi Epithelial cells Large circular folds Lacteal Key Nutrient absorption Intestinal wall Villi Lymph vessel Chapter 41: Animal Nutrition 1. Why do we eat? 2. What are the 4 main feeding mechanisms of feeding? 3. When our bodies need energy, what is the order of fuel usage? 4. How is appetite regulated in the body? 5. What happens if there is a mutation in the leptin system? 6. What are essential nutrient & what are the 4 classes? 7. What is the difference between malnourished & undernourished? 8. How is food processed? 9. What is the path that food takes through us? 10. Let’s find out what happens along the way? 11. What hormones control digestion? 12. How & where are nutrients absorbed? 13. How & where are fats absorbed? - Fats are emulsified by bile salts - Absorbed into the lacteal w/in the villi – lymph system Figure 41.24 Digestion and absorption of fats Fat globule 1 Large fat globules are emulsified by bile salts in the duodenum. Bile salts Digestion of fat by the pancreatic enzyme lipase yields free fatty acids and monoglycerides, which then form micelles. 2 Fat droplets coated with bile salts Micelles made up of fatty acids, monoglycerides, and bile salts 3 Fatty acids and monoglycerides leave micelles and enter epithelial cells by diffusion. Chylomicrons containing fatty substances are transported out of the epithelial cells and into lacteals, where they are carried away from the intestine by lymph. 4 Epithelial cells of small intestine Lacteal Chapter 41: Animal Nutrition 1. Why do we eat? 2. What are the 4 main feeding mechanisms of feeding? 3. When our bodies need energy, what is the order of fuel usage? 4. How is appetite regulated in the body? 5. What happens if there is a mutation in the leptin system? 6. What are essential nutrient & what are the 4 classes? 7. What is the difference between malnourished & undernourished? 8. How is food processed? 9. What is the path that food takes through us? 10. Let’s find out what happens along the way? 11. What hormones control digestion? 12. How & where are nutrients absorbed? 13. How & where are fats absorbed? - Fats are emulsified by bile salts - Absorbed into the lacteal w/in the villi – lymph system 14. What is the purpose of the large intestine? - Absorption of water – makes feces solid - Home of endosymbiotic bacteria Chapter 41: Animal Nutrition 1. Why do we eat? 2. What are the 4 main feeding mechanisms of feeding? 3. When our bodies need energy, what is the order of fuel usage? 4. How is appetite regulated in the body? 5. What happens if there is a mutation in the leptin system? 6. What are essential nutrient & what are the 4 classes? 7. What is the difference between malnourished & undernourished? 8. How is food processed? 9. What is the path that food takes through us? 10. Let’s find out what happens along the way? 11. What hormones control digestion? 12. How & where are nutrients absorbed? 13. How & where are fats absorbed? 14. What is the purpose of the large intestine? 15. What are some evolutionary adaptations of the vertebrate digestive system? - Teeth shape - Intestinal length - Symbiotic adaptations for fermentation in herbivores - Storage chambers Figure 41.26 Dentition and diet Incisors Canines (a) Carnivore (b) Herbivore (c) Omnivore Molars Premolars Figure 41.27 The digestive tracts of a carnivore (coyote) and herbivore (koala) compared Small intestine Small intestine Stomach Cecum Colon (large intestine) Carnivore Herbivore Figure 41.28 Ruminant digestion 1 Rumen. When the cow first chews and swallows a mouthful of grass, boluses (green arrows) enter the rumen. 2 Reticulum. Some boluses also enter the reticulum. In both the rumen and the reticulum, symbiotic prokaryotes and protists (mainly ciliates) go to work on the cellulose-rich meal. As by-products of their metabolism, the microorganisms secrete fatty acids. The cow periodically regurgitates and rechews the cud (red arrows), which further breaks down the fibers, making them more accessible to further microbial action. Intestine Esophagus 4 Abomasum. The cud, containing great numbers of microorganisms, finally passes to the abomasum for digestion by the cow‘s own enzymes (black arrows). 3 Omasum. The cow then reswallows the cud (blue arrows), which moves to the omasum, where water is removed.