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Chapter 41: Animal Nutrition

Chapter 41: Animal Nutrition. 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) What are the 4 main feeding mechanisms of animals? Suspension feeders Substrate feeder

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Chapter 41: Animal Nutrition

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  1. Chapter 41: Animal Nutrition • 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) • What are the 4 main feeding mechanisms of animals? • Suspension feeders • Substrate feeder • Fluid feeders • Bulk feeders

  2. Figure 41.2 Four Main Feeding Mechanisms of Animals SUSPENSION FEEDERS SUBSTRATE FEEDERS Feces Baleen Caterpillar FLUID FEEDERS BULK FEEDERS

  3. Chapter 41: Animal Nutrition • 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? • (fat- protein- carbs- ) • 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 2nd 3rd 1st

  4. 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 Leptin The hormone PYY,secreted by the small intestine after meals, acts as an appetite suppressant that counters the appetite stimulant ghrelin. 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. PYY Figure 41.5 A few of the appetite-regulating hormones

  5. Chapter 41: Animal Nutrition • 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? • (fat- protein- carbs- ) • 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 • What happens if there is a mutation in the leptin system? 2nd 3rd 1st

  6. Figure 41.6 A ravenous rodent

  7. Chapter 41: Animal Nutrition • 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

  8. Essential amino acids for adults Methionine Beansand other legumes Valine Threonine Phenylalanine Leucine Corn (maize)and other grains Isoleucine Tryptophan Lysine Figure 41.10 Essential amino acids from a vegetarian diet

  9. Table 41.1 Vitamin Requirements of Humans

  10. Table 41.2 Mineral Requirements of Humans

  11. Chapter 41: Animal Nutrition • 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 • What is the difference between malnourished & undernourished? • Under – get all essentials…just not enough • Mal – missing some essentials • 8. How is food processed?

  12. Smallmolecules Piecesof food Chemical digestion(enzymatic hydrolysis) Nutrient moleculesenter body cells Mechanicaldigestion Undigested material Food ELIMINATION ABSORPTION DIGESTION INGESTION 1 2 4 3 Figure 41.12 The four stages of food processing

  13. Chapter 41: Animal Nutrition • 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? • Mouthesophagusstomachsmall intestinelarge intestinerectumtoilet

  14. Salivaryglands Cardiacorifice Tongue Oral cavity Mouth Salivaryglands Pharynx Esophagus Esophagus Pyloricsphincter Gall-bladder Liver Stomach Ascendingportion of large intestine Gall-bladder Small intestines Liver Pancreas Pancreas IIeumof small intestine Large intestines Small intestine Duodenum of small intestine Anus Large intestine Rectum Appendix Anus Cecum Figure 41.15 The human digestive system Parotid gland Sublingual gland Submandibular gland Stomach Rectum A schematic diagram of the human digestive system

  15. Chapter 41: Animal Nutrition • 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? • Mouthesophagusstomachsmall intestinelarge intestinerectumtoilet • 10. Let’s find out what happens along the way?

  16. Bolus of food Tongue Epiglottisup Pharynx Esophageal sphinctercontracted Glottis Larynx Trachea Esophagus To lungs To stomach Figure 41.16 From mouth to stomach: the swallowing reflex and esophageal peristalsis (layer 1)

  17. Bolus of food Tongue Epiglottisup Pharynx Esophageal sphincterrelaxed Glottis Esophageal sphinctercontracted Epiglottis down Larynx Trachea Esophagus To lungs To stomach Glottis upand closed Figure 41.16 From mouth to stomach: the swallowing reflex and esophageal peristalsis (layer 2)

  18. Epiglottisup Bolus of food Tongue Glottisdown and open Epiglottisup Pharynx Esophageal sphincterrelaxed Esophageal sphinctercontracted Esophageal sphinctercontracted Glottis Epiglottis down Larynx Trachea Esophagus To lungs To stomach Glottis upand closed Contractedmuscles Relaxedmuscles Relaxedmuscles Figure 41.16 From mouth to stomach: the swallowing reflex and esophageal peristalsis (layer 3)

  19. Figure 41.21 Flowchart of enzymatic digestion in the human digestive system Protein digestion Fat digestion Nucleic acid digestion Carbohydrate digestion Oral cavity, pharynx, esophagus Polysaccharides (starch, glycogen) Disaccharides (sucrose, lactose) Salivary amylase Smaller polysaccharides, maltose Stomach Proteins Pepsin Small polypeptides Lumen of small intes- tine Fat globules (Insoluble in water, fats aggregate as globules.) Polypeptides Polysaccharides DNA, RNA Pancreatic trypsin and chymotrypsin (These proteases cleave bonds adjacent to certain amino acids.) Pancreatic amylases Pancreatic nucleases Bile salts Maltose and other disaccharides Fat droplets (A coating of bile salts prevents small drop- lets from coalescing into larger globules, increasing exposure to lipase.) Nucleotides Smaller polypeptides Pancreatic carboxypeptidase Pancreatic lipase Amino acids Glycerol, fatty acids, glycerides Epithelium of small intestine (brush border) Small peptides Nucleotidases Nucleosides Dipeptidases, carboxypeptidase, and aminopeptidase (These proteases split off one amino acid at a time, working from opposite ends of a polypeptide.) Disaccharidases Nucleosidases and phosphatases Monosaccharides Nitrogenous bases, sugars, phosphates Amino acids

  20. Esophagus Cardiac orifice Stomach Pyloric sphincter 5 µm Small intestine Folds of epithelial tissue Interior surface of stomach. The interior surface of the stomach wall is highly folded and dotted with pits leading into tubular gastric glands. Epithelium Pepsinogen Pepsin (active enzyme) 2 1 3 3 1 2 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. HCl Pepsinogen and HCI are secreted into the lumen of the stomach. HCl converts pepsinogen to pepsin. Mucus cells secrete mucus, which lubricates and protects the cells lining the stomach. Pepsin then activates more pepsinogen, starting a chain reaction. Pepsin begins the chemical digestion of proteins. Chief cells secrete pepsino- gen, an inactive form of the digestive enzyme pepsin. Parietal cell Chief cell Parietal cells secrete hydrochloric acid (HCl). Figure 41.17 The stomach and its secretions • stomach epithelium secretes gastric juice • parietal cells secrete HCl & chief cells secrete pepsinogen • pH = 2

  21. Liver Bile Gall-bladder Stomach Acid chyme Intestinaljuice Pancreatic juice Pancreas Duodenum of small intestine Figure 41.19 The duodenum

  22. Figure 41.21 Flowchart of enzymatic digestion in the human digestive system Protein digestion Fat digestion Nucleic acid digestion Carbohydrate digestion Oral cavity, pharynx, esophagus Polysaccharides (starch, glycogen) Disaccharides (sucrose, lactose) Salivary amylase Smaller polysaccharides, maltose Stomach Proteins Pepsin Small polypeptides Lumen of small intes- tine Fat globules (Insoluble in water, fats aggregate as globules.) Polypeptides Polysaccharides DNA, RNA Pancreatic trypsin and chymotrypsin (These proteases cleave bonds adjacent to certain amino acids.) Pancreatic amylases Pancreatic nucleases Bile salts Maltose and other disaccharides Fat droplets (A coating of bile salts prevents small drop- lets from coalescing into larger globules, increasing exposure to lipase.) Nucleotides Smaller polypeptides Pancreatic carboxypeptidase Pancreatic lipase Amino acids Glycerol, fatty acids, glycerides Epithelium of small intestine (brush border) Small peptides Nucleotidases Nucleosides Dipeptidases, carboxypeptidase, and aminopeptidase (These proteases split off one amino acid at a time, working from opposite ends of a polypeptide.) Disaccharidases Nucleosidases and phosphatases Monosaccharides Nitrogenous bases, sugars, phosphates Amino acids

  23. Pancreas Membrane-boundenteropeptidase Inactivetrypsinogen Trypsin Other inactiveproteases Active proteases Lumen of duodenum Figure 41.20 Protease activation

  24. Chapter 41: Animal Nutrition • 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? • Let’s find out what happens along the way? • What hormones control digestion? • CCK – cholecystokinin • Secretin • Gastrin • Enterogastrone

  25. 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 Entero- gastrone Gall- bladder Gastrin from the stomach recirculates via the bloodstream back to the stomach, where it stimulates the production of gastric juices. Gastrin CCK Stomach 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. Pancreas Secretin Duodenum Secreted by the duodenum, secretin stimulates the pancreas to release sodium bicarbonate, which neutralizes acid chyme from the stomach. CCK Key Stimulation Inhibition Figure 41.22 Hormonal control of digestion This ensures enzymes are only present when needed.

  26. Chapter 41: Animal Nutrition • 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? • Let’s find out what happens along the way? • What hormones control digestion? • How & where are nutrients absorbed? • Facilitated diffusion & active transport of monomers • Microvilli of small intestine

  27. Muscle layers Figure 41.23 The structure of the small intestine Microvilli(brush border) Vein carrying blood to hepatic portal vessel Bloodcapillaries Epithelialcells Epithelial cells Largecircularfolds Lacteal Villi Key Lymph vessel Villi Nutrientabsorption Intestinal wall

  28. Chapter 41: Animal Nutrition • 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? • Let’s find out what happens along the way? • What hormones control digestion? • How & where are nutrients absorbed? • How & where are fats absorbed? • Fats are emulsified by bile salts • Absorbed into the lacteal w/in the villi – lymph system

  29. Fat globule 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. Fat droplets coated with bile salts Micelles made up of fatty acids, monoglycerides, and bile salts 1 2 3 4 Fatty acids and mono-glycerides leave micelles and enter epithelial cells by diffusion. Chylomicrons containing fattysubstances are transported out of the epithelial cells and into lacteals, where they are carried away from the intestine by lymph. Epithelial cells of small intestine Lacteal Figure 41.24 Digestion and absorption of fats

  30. Chapter 41: Animal Nutrition • 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? • Let’s find out what happens along the way? • What hormones control digestion? • How & where are nutrients absorbed? • 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

  31. Chapter 41: Animal Nutrition • 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? • Let’s find out what happens along the way? • What hormones control digestion? • How & where are nutrients absorbed? • How & where are fats absorbed? • What is the purpose of the large intestine? • What are some evolutionary adaptations of the vertebrate digestive system? • Teeth shape • Intestinal length • Symbiotic adaptations for fermentation in herbivores • Storage chambers

  32. Figure 41.26 Dentition and diet Incisors Canines Molars (a) Carnivore Premolars (b) Herbivore (c) Omnivore

  33. Small intestine Stomach Small intestine Cecum Colon(large intestine) Figure 41.27 The digestive tracts of a carnivore (coyote) and herbivore (koala) compared Carnivore Herbivore

  34. Rumen. When the cow first chews and swallows a mouthful of grass, boluses (green arrows) enter the rumen. Intestine 1 2 3 4 Esophagus Abomasum. The cud, containing great numbers of microorganisms, finally passes to the abomasum for digestion by the cow‘s own enzymes (black arrows). Figure 41.28 Ruminant digestion 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. Omasum. The cow then reswallows the cud (blue arrows), which moves to the omasum, where water is removed.

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