Lecture 10 Outline (Ch. 41)

2. Lecture 10 Outline (Ch. 41) • I. Animal Nutrition Overview • II. Essential Parts of Animal Diet • III. Food Intake • Digestive Compartments • Adaptations • Obesity • 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. If a person is following a vegan diet, why is it recommended to eat a variety of plant sources? • Plants are not complete proteins • They are likely missing specific vitamins • Certain fatty acids may be missing • They may lack particular minerals • They do not contain chemical energy

9. 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

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

11. 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 Elimination is the passage of undigested material out of the digestive compartment Absorption is uptake of nutrients by body cells

12. 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

13. 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 called a complete digestive tract or an alimentary canal • Can have specialized regions, carry out digestion and absorption stepwise

14. 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

15. Food Epiglottisup Tongue Epiglottisup Pharynx Esophagealsphinctercontracted Epiglottisdown Glottis Glottisdownand open Esophagealsphinctercontracted Larynx Trachea Esophagus Esophagealsphincterrelaxed Glottis upand closed Relaxedmuscles Tolungs Tostomach Contractedmuscles Relaxedmuscles Sphincterrelaxed Stomach Oral Cavity, Pharynx, Esophagus • Food shaped into a bolus, lubricated by saliva, digestion begins with amylase and mucus • Pharynx, a junction that opens to both the esophagus and the trachea (windpipe) • The esophagus conducts food from the pharynx down to the stomach by peristalsis • Epiglottis blocks entry to the trachea, and larynx.

16. Esophagus Sphincter Stomach Sphincter 5 µm Small intestine Folds ofepithelialtissue Interior surfaceof stomach Epithelium 3 Pepsinogen Pepsin 2 HCl Gastric gland 1 Mucus cells H+ Cl– Chief cells Chief cell Parietal cells 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

17. Digestion in the Small Intestine • The small intestine: longest section of alimentary canal • Major organ of enzymatic digestion and absorption • First is the duodenum - acid chyme from the stomach mixes with digestive juices from the pancreas, liver, gallbladder, and the small intestine itself.

18. 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

19. Where are most fats broken and absorbed? • In the mouth • In the stomach • In the liver • In the gall bladder • In the small intestine

20. Carbohydrate digestion Protein digestion Nucleic acid digestion Fat digestion Oral cavity,pharynx,esophagus Disaccharides Polysaccharides (starch, glycogen) (sucrose, lactose) Salivary amylase Smaller polysaccharides,maltose Stomach Proteins Pepsin Small polypeptides Lumen ofsmall intestine DNA, RNA Fat globules Polypeptides Polysaccharides Pancreatic amylases Pancreatic trypsin andchymotrypsin Pancreatic nucleases Bile salts Maltose and otherdisaccharides Fat droplets Nucleotides Smallerpolypeptides Pancreatic lipase Pancreatic carboxypeptidase Glycerol, fattyacids, monoglycerides Amino acids Epitheliumof smallintestine(brushborder) Small peptides Nucleotidases Nucleosides Disaccharidases Dipeptidases, carboxypeptidase,and aminopeptidase Nucleosidasesandphosphatases Nitrogenous bases,sugars, phosphates Monosaccharides Amino acids

21. Microvilli (brushborder) at apical(lumenal) surface Vein carrying bloodto hepatic portal vein Lumen Bloodcapillaries Epithelialcells Basal surface Muscle layers Largecircularfolds Epithelial cells Villi Lacteal Key Lymphvessel Nutrientabsorption Villi Intestinal wall Absorption in the Small Intestine • small intestine has huge surface area, from villi and microvilli exposed to the intestinal lumen • enormous microvillar surface greatly increases rate of nutrient absorption

22. 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

23. 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)

24. 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

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

26. Where is most water absorbed? • In the stomach • In the small intestine • In the cecum • In the large intestine • In the bladder

27. 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 • When fewer calories are taken in than are expended, fuel is taken from storage and oxidized • Obesity is due to excessive intake of food energy, excess stored as fat • Obesity contributes to diabetes (type 2), cancer of the colon and breasts, heart attacks, and strokes

28. 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

29. If you eat a meal high in sugar, what happens? • Glucagon is released • Glycogen is broken down • Insulin is released • Fats are broken down • Starch is stored

30. 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

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

32. The gene db codes for the leptin receptor. If mice are mutant for the db gene what happens? • They fail to make leptin – increased appetite • They fail to detect leptin – decreased appetite • They fail to detect leptin – increased appetite • They fail to make leptin – decreased appetite

33. 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?