Lecture 10 Outline (Ch. 41)

2. Lecture 10 Outline (Ch. 41) I. Animal Nutrition Overview • Food Intake • Digestive Compartments • Adaptations • Energy sources and stores • Preparation for next lecture

3. Overview: The Need to Feed • Food is taken in, taken apart, and taken up in the process of animal nutrition • In general, animals fall into three categories: • Herbivores eat mainly autotrophs (plants, algae) • Carnivores eat other animals • Omnivores regularly consume animals as well as plants or algal matter

4. Essential Parts of Diet • Chemical energy (converted to ATP) • Organic carbon and nitrogen • Essential nutrients must be obtained from dietary sources • Essential amino acids • Essential fatty acids • Vitamins • Minerals

5. Essential amino acids for adults Methionine Beans and other legumes Valine Threonine Phenylalanine Leucine Corn (maize)and other grains Isoleucine Tryptophan Lysine Essential Parts of Diet • Meat, eggs, cheese - provide all nine essential amino acids ( “complete” proteins) • Individuals eating only plant proteins need specific plant combinations for all essential amino acids

6. Essential Parts of Diet • Animals can synthesize most fatty acids they need • The essential fatty acids are certain unsaturated fatty acids that must be obtained from the diet • Vitamins: organic molecules needed in small amounts • 13 essential vitamins for humans • Fat-soluble & water-soluble Vitamin A Vitamin D Vitamin E Vitamin K B-complex Biotin/B7 Vitamin C (ascorbic acid)

7. Minerals Calcium Phosphorus Potassium Sulfur Chlorine Sodium Magnesium Iron • Minerals: inorganic nutrients, small amounts needed A diet missing a certain essential part or not enough calories overall leads to malnourishment or undernourishment

8. Food Intake Ingestion: the act of eating • Suspension feeders - many aquatic animals, which sift small food particles from the water • Substrate feeders are animals that live in or on their food source • Fluid feeders suck nutrient-rich fluid from a living host • Bulk feeders eat relatively large pieces of food

9. Leaf miner caterpillar, substrate feeder Baleen Humpback whale, a suspension feeder Caterpillar Feces Mosquito, a fluid feeder Rock python, a bulk feeder

10. Smallmolecules Piecesof food Chemical digestion(enzymatic hydrolysis) Nutrientmoleculesenter bodycells Mechanicaldigestion Undigestedmaterial Food Ingestion Digestion Elimination Absorption 2 4 1 3 Food Intake Digestion: process of breaking food down into molecules small enough to absorb. In chemical digestion, enzymatic hydrolysis splits bonds in molecules Absorption is uptake of nutrients by body cells Elimination is the passage of undigested material out of the digestive compartment

11. Tentacles Gastrovascularcavity Food Mouth Epidermis Gastrodermis Digestive Compartments • Most animals process food (i.e. hydrolysis) in specialized compartments • Reduces risk animal digesting its own cells/ tissues Gastrovascular Cavity: For both digestion and distribution of nutrients Cells secrete digestive enzymes

12. Crop Gizzard Intestine Esophagus Pharynx Anus Mouth Typhlosole Lumen of intestine (a) Earthworm Foregut Midgut Hindgut Rectum Esophagus Anus Crop Mouth Gastric cecae (b) Grasshopper Stomach Gizzard Intestine Mouth Esophagus Crop Anus (c) Bird Digestive Compartments • More complex animals: digestive tube with two openings (mouth, anus) “Tube within a tube” • Called alimentary canal • Specialized regions, carry out digestion and absorption stepwise

13. Tongue Sphincter Salivaryglands Oral cavity Mouth Salivary glands Pharynx Esophagus Esophagus Sphincter Liver Stomach Gall-bladder Stomach Ascendingportion oflarge intestine Gall-bladder Duodenum ofsmall intestine Smallintestine Pancreas Liver Smallintestine Smallintestine Pancreas Largeintestine Largeintestine Rectum Rectum Anus Anus Appendix A schematic diagram of thehuman digestive system Cecum Digestive Compartments Food moves by peristalsis • Mammalian alimentary canal and accessory glands that secrete digestive juices through ducts

14. Food Tongue Epiglottisup Pharynx Epiglottisdown Larynx Trachea Esophagus Esophagealsphincterrelaxed Relaxedmuscles Tolungs Tostomach Contractedmuscles Relaxedmuscles Sphincterrelaxed Stomach Oral Cavity, Pharynx, Esophagus • Food  bolus, saliva added, digestion begins with amylase and mucus • Pharynx, junction opens to both the esophagus and the trachea (windpipe) • Esophagus conducts food pharynx to stomach by peristalsis • Epiglottis blocks entry to the trachea, and larynx.

15. Esophagus Sphincter Stomach Sphincter 5 µm Small intestine Folds ofepithelialtissue Epithelium 3 Pepsinogen Pepsin 2 HCl Gastric gland 1 Mucus cells H+ Cl– Chief cell Parietal cell Digestion in the Stomach • The stomach stores food and secretes gastric juice, which converts a meal to acid chyme • Highly folded • Gastric juice - hydrochloric acid (parietal cells) and the enzyme pepsin (chief cells) • Pepsin initially secreted as pepsinogen • Mucus protects the stomach lining from gastric juice

16. Digestion in the Small Intestine • The small intestine: longest section of alimentary canal • Major organ of enzymatic digestion and absorption • 1st: duodenum • acid chyme from stomach mixes with digestive juices from pancreas, liver, gallbladder, and the small intestine itself. • 2nd: jejunum • 3rd: ileum

17. Digestion in the Small Intestine pancreas proteases trypsin & chymotrypsin amylase & lipase bicarbonate neutralizes the acidic chyme liver/gallbladder bile aids digestion and absorption of fats small intestine lining of duodenum (brush border) produces several digestive enzymes jejunum and ileum mainly absorb water & nutrients

18. Carbohydrate digestion Oral cavity, pharynx, esophagus Polysaccharides Disaccharides Salivary amylase Smaller polysaccharides Maltose Protein digestion Proteins Stomach Pepsin Small polypeptides Nucleic acid digestion Fat digestion Fat (triglycerides) DNA, RNA Small intestine (enzymes from pancreas) Pancreatic amylases Pancreatic trypsin and chymotrypsin Pancreatic nucleases Disaccharides Smaller polypeptides Nucleotides Pancreatic lipase Pancreatic carboxypeptidase Glycerol, fatty acids, monoglycerides Small peptides Nucleotidases Dipeptidases, carboxy- peptidase, and aminopeptidase Small intestine (enzymes from epithelium) Nucleosides Disaccharidases Nucleosidases and phosphatases Nitrogenous bases, sugars, phosphates Amino acids Monosaccharides

19. Absorption in the Large Intestine • The colon of the large intestine is connected to the small intestine • The cecum aids in fermentation of plant material, • - connects where the small and large intestines meet • Human cecum extension (appendix),-minor role in immunity Feces stored in rectum until eliminated

20. Absorption in the Large Intestine • The colon houses strains of the bacterium Escherichia coli, some of which produce vitamins • Two sphincters between the rectum and anus control bowel movements • Internal smooth muscle sphincter (involuntary) • External striated muscle sphincter (voluntary)

21. Rumen Reticulum 1 2 Intestine Esophagus Abomasum Omasum 4 3 Mutualistic Adaptations • Many herbivores have symbiotic microorganisms that digest cellulose • The most elaborate adaptations in ruminants

22. Small intestine Stomach Small intestine Cecum Colon(largeintestine) Carnivore Herbivore Adaptations • Herbivores generally longer alimentary canals than carnivores; longer time needed to digest vegetation • Coprophagy – method to recover more nutrients by ingesting feces Enzymes for digesting plant matter

23. Energy Sources and Stores Pancreas releases insulin – cells uptake sugars Stimulus:Blood glucoselevel risesafter eating. Homeostasis:90 mg glucose/ 100 mL blood Stimulus:Blood glucoselevel dropsbelow set point. Pancreas releases glucagon – liver releases sugars

24. 100 µm Fat cells Energy Sources and Stores • Animals store excess calories as glycogen in the liver and muscles • Energy secondarily stored as adipose, or fat, cells • Fewer calories taken in than expended  fuel is taken from storage and oxidized • Excessive intake of food energy, excess stored as fat • Obesity contributes to diabetes (type 2), colon and breast cancer, heart attacks, and strokes

25. Ghrelin Insulin Leptin PYY Energy Sources and Stores hypothalamus • The complexity of weight control in humans is well-studied • Mice that inherit a defect in the gene for leptin become very obese Ghrelin – secreted by stomach, stimulates appetite Insulin – secreted by pancreas, suppresses appetite Leptin – released by fat cells, suppresses appetite PYY – secreted by Sm. Intestine, suppresses appetite

26. Obese mouse with mutant ob gene (left) – mutant for leptin production – next to wild-type sibling mouse.

27. Things To Do After Lecture 10… Reading and Preparation: • Re-read today’s lecture, highlight all vocabulary you do not understand, and look up terms. • Ch. 41 Self-Quiz: #2, 3, 4, 5, 6 (correct answers in back of book) • Read chapter 41, focus on material covered in lecture (terms, concepts, and figures!) • Skim next lecture. “HOMEWORK” (NOT COLLECTED – but things to think about for studying): • Describe the pathway that food molecules take from ingestion through elimination – where appropriate, indicate which digestive enzymes are secreted and what biomolecules are broken down. • Define, and then list: necessary vitamins and minerals. • Explain the difference between a substrate feeder and a bulk feeder. • Compare the function of leptin and ghrelin – where and when are each secreted/released?