Chapter 41: Animal Nutrition

1. Chapter 41: Animal Nutrition

2. 3 dietary categories • Herbivores eat mainly autotrophs (plants and algae) • Carnivores eat other animals • Omnivores consume animals as well as plants or algal matter

3. Diet • An adequate diet must satisfy 3 nutritional needs • Chemical energy for all cellular work • The organic raw materials for biosynthesis • Essential nutrients, substances such as vitamins that the animal cannot make for itself

4. Why We Eat • Animal’s diet must supply carbon skeletons and essential nutrients

5. Essential Amino Acids • Animals require 20 amino acids • Synthesize about half of them from the other molecules they obtain from their diet • Essential amino acids • Must be obtained from food in preassembled form

6. Amino Acids

7. A diet that provides insufficient amounts of one or more essential amino acids causes protein deficiency Figure 41.9

8. Essential amino acids for adults Beansand other legumes Methionine Valine Threonine Phenylalanine Leucine Corn (maize)and other grains Isoleucine Tryptophan Lysine Figure 41.10 • Most plant proteins are incomplete in amino acid makeup •  eat a variety to get all the essential amino acids

9. Vitamins • Vitamins are organic molecules • Required in the diet in small amounts • To date, 13 vitamins essential to humans • Have been identified

10. Vitamins: Water Soluble

11. Vitamins: Fat Soluble

12. Minerals • Simple inorganic nutrients • Usually required in small amounts

13. Mineral requirements of humans

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

15. Cardiacorifice Tongue Oral cavity Salivaryglands Pharynx Parotid gland Sublingual gland Esophagus Submandibular gland Pyloricsphincter Liver Stomach Gall-bladder Ascendingportion of large intestine Pancreas IIeumof small intestine Small intestine Duodenum of small intestine Large intestine Rectum Appendix Anus Cecum Basic Set up of our Digestive System

16. The Oral Cavity, Pharynx, and Esophagus • Digestion begins • And teeth chew food into smaller particles that are exposed to salivary amylase, initiating the breakdown of carbohydrates into glucose polymers

17. The Stomach • Secretes gastric juice, which converts a meal to acid chyme • Gastric juice • Hydrochloric acid and the enzyme pepsin • pH around 2

18. Liver Stomach Bile Gall-bladder Acid chyme Intestinaljuice Pancreas Pancreatic juice Duodenum of small intestine Enzymatic Action in the Small Intestine • First portion of the small intestine (duodenum) • Acid chyme from stomach mixes with digestive juices from the pancreas, liver, gallbladder, and intestine itself Figure 41.19

20. Pancreas Membrane-boundenteropeptidase Inactivetrypsinogen Trypsin Other inactiveproteases Active proteases Lumen of duodenum The Pancreas • The pancreas produces proteases, protein-digesting enzymes • That are activated once they enter the duodenum pH change Figure 41.20

21. Enterogastronesecreted by the duodenum inhibits peristalsis and acid secretion by the stomach, thereby slowing digestion when acid chyme rich in fats enters the duodenum. 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 Entero- gastrone Gall- bladder Gastrin from the stomach stimulates the production of gastric juices. Gastrin CCK Stomach Pancreas Secreted by the duodenum, secretin stimulates the Pancreas to release sodium bicarbonate, which neutralizes acid chyme from the stomach. Secretin Duodenum CCK Key Stimulation Inhibition Hormones control the secretion of digestive enzymes

22. Microvilli(brush border) Vein carrying blood to hepatic portal vessel Bloodcapillaries Muscle layers Epithelialcells Epithelial cells Largecircularfolds Lacteal Villi Key Lymph vessel Villi Nutrientabsorption Intestinal wall Small Intestine: Organ of digestion and absorption • The enormous microvillar surface area • Greatly increases the rate of nutrient absorption Figure 41.23

23. Homeostatic mechanisms tell us what we need • Homeostatic mechanisms manage animal’s energy budget • Animal’s ATP generation • Based on the oxidation of energy-rich molecules: carbohydrates, proteins, and fats

24. Glucose Regulation as an Example of Homeostasis • Animals store excess calories • As glycogen in the liver and muscles and as fat

25. When blood glucose level rises, a gland called the pancreas secretes insulin, a hormone, into the blood. 1 Insulin enhances the transport of glucose into body cells and stimulates the liver and muscle cells to store glucose as glycogen. As a result, blood glucose level drops. 2 Glucagon promotesthe breakdown ofglycogen in theliver and the release of glucose into the blood, increasing bloodglucose level. 4 When blood glucose level drops, the pancreas secretes the hormone glucagon, which opposes the effect of insulin. 3 Glucose  major fuel for cells • Its metabolism, regulated by hormone action, is an important example of homeostasis STIMULUS: Blood glucose level rises after eating. Homeostasis: 90 mg glucose/ 100 mL blood STIMULUS: Blood glucose level drops below set point. Figure 41.3

26. Secreted by the stomach wall, ghrelin is one of the signals that triggers feelings of hunger at mealtimes. In dieters who lose weight, ghrelin increases, which may be one reason it’s so hard to stay on a diet. Leptin produced by Fat cells Ghrelin Insulin Leptin The hormonePYY,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 insulin suppresses appetite by acting on the brain. PYY Hormones regulate appetite (Controlled by Brain) CCK inhibits gastric emptying. It stimulates the pancreas to release digestive enzymes. Released by duodenum.

27. Mice that inherit a defect in the gene for leptin • Become very obese Figure 41.6