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Why do we crave pizza so? Why do we crave pizza so? How does a pizza help you make brain cells? Or a lean fish help a bear make fat? LECTURE PRESENTATIONS For CAMPBELL BIOLOGY, NINTH EDITION Jane B. Reece, Lisa A. Urry, Michael L. Cain, Steven A. Wasserman, Peter V. Minorsky, Robert B. Jackson Chapter 41 Animal Nutrition Lectures by Erin Barley Kathleen Fitzpatrick © 2011 Pearson Education, Inc. Video: Lobster Mouth Parts © 2011 Pearson Education, Inc. Video: Shark Eating a Seal © 2011 Pearson Education, Inc. Concept 41.1: An animal’s diet must supply chemical energy, organic molecules, and essential nutrients • An animal’s diet provides: 1. Chemical energy, which is converted into ATP to power cellular processes 2. Organic building blocks, such as organic carbon and organic nitrogen, to synthesize a variety of organic molecules 3. Essential nutrients, which are required by cells and must be obtained from dietary sources © 2011 Pearson Education, Inc. Essential Nutrients • There are four classes of essential nutrients: 1. 2. 3. 4. Essential amino acids Essential fatty acids Vitamins - organic Minerals - inorganic © 2011 Pearson Education, Inc. What is the problem with a vegan diet? © 2011 Pearson Education, Inc. What is the problem with a vegan diet? • Animals require 20 amino acids and can synthesize about half from molecules in their diet • The remaining amino acids, the essential amino acids, must be obtained from food in preassembled form © 2011 Pearson Education, Inc. Table 41.1 Table 41.2 Figure 41.3 Why is this fella licking the ground? Assessing Nutritional Needs What is the difference between malnourishment and undernourishment? • Insights into human nutrition have come from epidemiology, the study of human health and disease in populations • Example: neural tube defects were found to be the result of a deficiency in folic acid in pregnant mothers © 2011 Pearson Education, Inc. Can diet influence the frequency of birth defects? RESULTS Number of infants/fetuses studied Infants/fetuses with a neural tube defect Vitamin supplements (experimental group) 141 1 (0.7%) No vitamin supplements (control group) 204 12 (5.9%) Group •Concept 41.2: The main stages of food processing are ingestion, digestion, absorption, and elimination Mechanical digestion 1 Ingestion Nutrient molecules enter body cells Chemical digestion (enzymatic hydrolysis) 2 Digestion Undigested material 3 Absorption 4 Elimination Figure 41.6 Suspension Feeders and Filter Feeders Baleen Substrate Feeders Fluid Feeders Caterpillar Feces Bulk Feeders Video: Hydra Eating Daphnia © 2011 Pearson Education, Inc. Figure 41.7 Mouth Tentacles Food 1 Digestive enzymes released 2 Food particles broken down 3 Food particles engulfed and digested Epidermis Gastrodermis Esophagus Crop Gizzard Intestine Pharynx Variation in alimentary canals. Anus Mouth (a) Earthworm Foregut Midgut Hindgut Esophagus Rectum Anus Esophagus Crop Stomach Gizzard Intestine Mouth Anus Crop Gastric cecae Mouth (b) Grasshopper (c) Bird Consistent layout of most mammals Tongue Oral cavity Salivary glands Mouth Pharynx Esophagus Salivary glands Esophagus Liver Sphincter Gallbladder Pancreas Small intestine Large intestine Rectum Anus Sphincter Stomach Gallbladder Liver Pancreas Stomach Small intestine Large intestine Rectum Anus Schematic diagram Duodenum of small intestine peristalsis Tongue Bolus of food Pharynx Epiglottis up Glottis Larynx Trachea Esophageal sphincter contracted Esophagus To lungs To stomach peristalsis Tongue Bolus of food Pharynx Epiglottis up Glottis Larynx Trachea Esophageal sphincter contracted Esophagus To lungs To stomach peristalsis Tongue Bolus of food Pharynx Epiglottis up Glottis Larynx Trachea Esophageal sphincter contracted Esophagus To lungs To stomach Relaxed muscles Contracted muscles Sphincter relaxed Stomach Digestion in the Stomach • The stomach stores food and secretes gastric juice, which converts a bolus to acid chyme © 2011 Pearson Education, Inc. Chemical Digestion in the Stomach • Gastric juice has a low pH of about 2, which kills bacteria and denatures proteins – Gastric juice is made up of hydrochloric acid (HCl) and pepsin • Pepsin is a protease, or protein-digesting enzyme, that cleaves proteins into smaller peptides © 2011 Pearson Education, Inc. Why doesn’t the stomach digest itself? Figure 41.11 Esophagus Sphincter Stomach 10 m Sphincter Gastric pits on interior surface of stomach Small intestine Folds of epithelial tissue Epithelium 3 Pepsinogen Pepsin 2 Gastric gland Mucous cell Chief cell Parietal cell HCl Chief cell 1 Cl H Parietal cell Chemical digestion in the human digestive system. Carbohydrate digestion Oral cavity, Polysaccharides pharynx, esophagus Salivary amylase Smaller Maltose polysaccharides Figure 41.12-2 Carbohydrate digestion Oral cavity, Polysaccharides pharynx, esophagus Salivary amylase Smaller Maltose polysaccharides Stomach Protein digestion Proteins Pepsin Small polypeptides Figure 41.12-3 Carbohydrate digestion Oral cavity, Polysaccharides pharynx, esophagus Salivary amylase Smaller Maltose polysaccharides Stomach Protein digestion Proteins Pepsin Small polypeptides Small intestine (enzymes from pancreas) Pancreatic amylases Pancreatic trypsin and chymotrypsin Nucleic acid digestion Fat digestion DNA, RNA Fat (triglycerides) Pancreatic nucleases Disaccharides Smaller polypeptides Nucleotides Pancreatic lipase Pancreatic carboxypeptidase Small peptides Glycerol, fatty acids, monoglycerides Figure 41.12-4 Carbohydrate digestion Oral cavity, Polysaccharides Disaccharides pharynx, esophagus Salivary amylase Smaller Maltose polysaccharides Stomach Protein digestion Proteins Pepsin Small polypeptides Small intestine (enzymes from pancreas) Pancreatic amylases Pancreatic trypsin and chymotrypsin Nucleic acid digestion Fat digestion DNA, RNA Fat (triglycerides) Pancreatic nucleases Disaccharides Smaller polypeptides Nucleotides Pancreatic lipase Pancreatic carboxypeptidase Glycerol, fatty acids, monoglycerides Small peptides Small intestine (enzymes from epithelium) Disaccharidases Dipeptidases, carboxypeptidase, and aminopeptidase Nucleotidases Nucleosides Nucleosidases and phosphatases Monosaccharides Amino acids Nitrogenous bases, sugars, phosphates Most of absorption happens in the small intestine • 15 – 32 feet in humans • The first portion of the small intestine is the duodenum, where chyme from the stomach mixes with digestive juices from the pancreas, liver, gallbladder, and the small intestine itself – Most of nutrient digestion here – Jejunum and ilium mostly extract water – Some nutrients diffuse through membranes, most are pumped against gradient © 2011 Pearson Education, Inc. Pancreatic Secretions • The pancreas produces proteases trypsin and chymotrypsin that are activated in the lumen of the duodenum • Its solution is alkaline…Why? © 2011 Pearson Education, Inc. Bile Production by the Liver • In the small intestine, bile aids in digestion and absorption of fats • Bile is made in the liver and stored in the gallbladder • Bile also destroys nonfunctional red blood cells © 2011 Pearson Education, Inc. Figure 41.13 Nutrient absorption in the small intestine. Vein carrying blood to liver Villi Microvilli (brush border) at apical (lumenal) surface Epithelial cells Blood capillaries Epithelial cells Muscle layers Villi Intestinal wall Large circular folds Basal surface Lacteal Key Nutrient absorption •membrane transport review bioflix Lymph vessel Lumen • The hepatic portal vein carries nutrient-rich blood from the capillaries of the villi to the liver, then to the heart • The liver regulates nutrient distribution, interconverts many organic molecules, and detoxifies many organic molecules © 2011 Pearson Education, Inc. Figure 41.15 •The colon’s primary purpose is to absorb water from chyme. Ascending portion of colon Small intestine Cecum Appendix •90% of water consumed is reabsorbed. •What happens if too much is absorbed? Too little? Symbiotic bacteria and digestion • There are approximately 500 species of bacteria comprising the gut flora (part of the “human microbiome”) that aid in digestion – 100 trillion cells compared to 10 trillion actual body cells Why don’t we eat feces? © 2011 Pearson Education, Inc. Symbiotic bacteria and digestion • There are approximately 500 species of bacteria comprising the gut flora (part of the “human microbiome”) that aid in digestion – 100 trillion cells compared to 10 trillion actual body cells Why don’t we eat feces? 30% of dry weight of feces is bacteria. • Dogs and gorillas practice coprophagia for different reasons. Why? proof © 2011 Pearson Education, Inc. • Feces are stored in the rectum until they can be eliminated through the anus • Two sphincters between the rectum and anus control bowel movements, the top being involuntary, the bottom (anus) being voluntary © 2011 Pearson Education, Inc. Stomach and Intestinal Adaptations • Many carnivores have large, expandable stomachs • Herbivores and omnivores generally have longer alimentary canals than carnivores, reflecting the longer time needed to digest vegetation © 2011 Pearson Education, Inc. Figure 41.17 Small intestine Small intestine Stomach Cecum Carnivore Colon (large intestine) Herbivore Figure 41.18 2 Reticulum 1 Rumen Esophagus Intestine 4 Abomasum 3 Omasum Concept 41.5: Feedback circuits regulate digestion, energy storage, and appetite • Each step in the digestive system is activated as needed • The enteric division of the nervous system helps to regulate the digestive process • The endocrine system also regulates digestion through the release and transport of hormones © 2011 Pearson Education, Inc. Hormonal control of digestion. 1 2 Food 3 Bile Liver Stomach Secretin and CCK Chyme Gallbladder Gastric juices Gastric juices CCK Pancreas Duodenum of small intestine HCO3, enzymes Secretin Key Stimulation Inhibition Gastrin CCK Regulation of Energy Storage • The body stores energy-rich molecules that are not needed right away for metabolism • In humans, energy is stored first in the liver and muscle cells in the polymer glycogen – Excess energy is stored in adipose tissue, the most space-efficient storage tissue © 2011 Pearson Education, Inc. Glucose Homeostasis • Oxidation of glucose generates ATP to fuel cellular processes • The hormones insulin and glucagon regulate the breakdown of glycogen into glucose • The liver is the site for glucose homeostasis – A carbohydrate-rich meal raises insulin levels, which triggers the synthesis of glycogen – Low blood sugar causes glucagon to stimulate the breakdown of glycogen and release glucose Blood sugar regulation bioflix © 2011 Pearson Education, Inc. Figure 41.20 Transport of glucose into body cells and storage of glucose as glycogen Pancreas secretes insulin. Stimulus: Blood glucose level rises after eating. Homeostasis: 70–110 mg glucose/ 100 mL blood Breakdown of glycogen and release of glucose into blood Stimulus: Blood glucose level drops below set point. Pancreas secretes glucagon. Satiety center Faulty appetiteregulating hormones can lead to obesity Ghrelin Insulin Leptin PYY Figure 41.22 EXPERIMENT Obese mouse with mutant ob gene (left) next to wild-type mouse RESULTS Genotype pairing (red type indicates mutant genes) Average change in body mass (g) of subject Subject Paired with obob , dbdb obob , dbdb 8.3 ob ob, dbdb ob ob, dbdb 38.7 ob ob, dbdb obob, dbdb 8.2 ob ob, dbdb obob, db db 14.9* *Due to pronounced weight loss and weakening, subjects in this pairing were reweighed after less than eight weeks. What is the point, evolutionarily, of binge eating? Dentition and diet. Carnivore Herbivore Key Incisors Omnivore Canines Premolars Molars •See 10-1, and also 10-2 FRQ du jour Homeostatic maintenance of optimal blood glucose levels has been intensively studied in vertebrate organisms. (a) Pancreatic hormones regulate blood glucose levels. Identify TWO pancreatic hormones and describe the effect of each hormone on blood glucose levels. (b) For ONE of the hormones you identified in (a), identify ONE target cell and discuss the mechanism by which the hormone can alter activity in that target cell. Include in your discussion a description of reception, cellular transduction, and response. (c) Compare the cell-signaling mechanisms of steroid hormones and protein hormones.
