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 Fluid feeders Bulk feeders

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

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

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

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

Figure 41.6 A ravenous rodent

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
Corn (maize) and other grains Beans and other legumes Essential amino acids for adults Methionine Valine Threonine Phenylalanine Leucine Isoleucine Lysine Tryptophan

Table 41.1 Vitamin Requirements of Humans

Table 41.2 Mineral Requirements of Humans

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?

Figure 41.12 The four stages of food processing
Pieces of food Small molecules Mechanical digestion Food Chemical digestion (enzymatic hydrolysis) Nutrient molecules enter body cells Undigested material INGESTION 1 DIGESTION 2 ELIMINATION 4 ABSORPTION 3

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

Figure 41.15 The human digestive system
IIeum of small intestine Duodenum of small intestine Tongue Cardiac orifice Salivary glands Oral cavity Parotid gland Mouth Salivary glands Sublingual gland Pharynx Submandibular gland Esophagus Esophagus Pyloric sphincter Liver Stomach Gall- bladder Stomach Ascending portion of large intestine Gall- bladder Small intestines Liver Pancreas Pancreas Large intestines Small intestine Rectum Large intestine Anus Rectum A schematic diagram of the human digestive system Anus Appendix Cecum

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?

Figure 41.16 From mouth to stomach: the swallowing reflex and esophageal peristalsis (layer 1)
Esophagus Tongue Pharynx Glottis Larynx Trachea Bolus of food Epiglottis up To lungs To stomach Esophageal sphincter contracted

Esophagus Epiglottis down Tongue Pharynx Glottis Larynx Trachea Bolus of food Epiglottis up To lungs To stomach Esophageal sphincter contracted Glottis up and closed Esophageal sphincter relaxed

Esophagus Epiglottis down Tongue Pharynx Glottis Larynx Trachea Bolus of food Epiglottis up To lungs To stomach Esophageal sphincter contracted Glottis up and closed Esophageal sphincter relaxed Glottis down and open Relaxed muscles Contracted muscles

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

Figure 41.17 The stomach and its secretions
Pepsin (active enzyme) HCl Parietal cell Chief cell Stomach Folds of epithelial tissue Esophagus Pyloric sphincter Epithelium Pepsinogen 3 2 1 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. 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 cells secrete hydrochloric acid (HCl). Pepsinogen and HCI are secreted into the lumen of the stomach. HCl converts pepsinogen to pepsin. Pepsin then activates more pepsinogen, starting a chain reaction. Pepsin begins the chemical digestion of proteins. 5 µm Small intestine Cardiac orifice stomach epithelium secretes gastric juice parietal cells secrete HCl & chief cells secrete pepsinogen pH = 2

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

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

Figure 41.20 Protease activation
Pancreas Membrane-bound enteropeptidase Trypsin Active proteases Lumen of duodenum Inactive trypsinogen Other inactive proteases

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

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

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

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 Epithelial cells Large circular folds Lacteal Villi Key Lymph vessel Nutrient absorption Villi Intestinal wall

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

Figure 41.24 Digestion and absorption of fats
Large fat globules are emulsified by bile salts in the duodenum. Fat globule Lacteal Epithelial cells of small intestine Micelles made up of fatty acids, monoglycerides, and bile salts Fat droplets coated with bile salts Bile salts Digestion of fat by the pancreatic enzyme lipase yields free fatty acids and monoglycerides, which then form micelles. 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. 1 2 3 4

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

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

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

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

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

Chapter 41: Animal Nutrition

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