1. Lecture 25, 02 Dec 2003 Chapter 15, Feeding and Digestion Chapter 16, Energy Expenditure, Body Size Vertebrate Physiology ECOL 437 University of Arizona Fall 2003 instr: Kevin Bonine t.a.: Bret Pasch 1

2. Vertebrate Physiology 437 1. Feeding and Digestion (CH15) 2. ~Energy Expenditure (CH16) 3. Announcements… - Term paper 04 Dec. - Seminar write-up 09 Dec. - Powerpoint (file to us on 09 Dec.) - Oral Presentations 10 Dec. (8min) - Movie and Thanksgiving Assgt due Wed - Read Ch17 for Thurs lecture - Friday Physiology Seminar (calcium regulation in endothelial cells) 2

3. ABSORPTION: -Across epithelium of brush border (microvilli) -Glycocalyx has enzymes for final cleavage disaccharidases, aminopeptidases, phosphatases -Simple Diffusion 1 fat-soluble substances 2 small water soluble substances through regulated aquaporins 3 down concentration or electrochemical gradients -Facilitated Diffusion 1 monosaccharides and amino acids 2 transporter proteins 3 down conc. gradient or 4 coupled to Na + gradient (Na/K-ATPase) 3

4. (15-37) 4

5. ABSORPTION -Active Transport -amino acids with ~specific transporters coupled to Na+ -Lipids -products cross into epithelial cells (monoglycerides, fatty acids, glycerol) -reconstructed into triglycerides -formed into chylomicrons using cholesterol and phospholipids -chylomicrons exocytosed -taken into central lacteal and into lymph system 5

6. (15-38) Lipids 6 ER Golgi Lacteal

7. Nutrient Transport in Blood -lipids (chylomicrons) into blood from lymph at thoracic duct -sugars and amino acids into capillaries of villi -to liver via hepatic portal vein sugars converted to glycogen for storage 7

8. Water and Electrolyte Balance in Gut -Lots of water and electrolytes secreted into lumen -Need to recover -Most via lower small intestine (ileum) -Osmotic gradient b/c absorb salts, carbos, amino acids -Tips of villi -Countercurrent exchange with high Na+ (Cl - follows) to facilitate water reabsorption 8

9. (15-39) Secretions etc. = 9 ileum

10. Nutritional Requirements… (Essential?) 10

11. Chapter 16 Energy Expenditure -temperature -size -activity 11

12. Metabolism -Chemical reactions in the body -Temperature dependent rates -Not 100% efficient, energy lost as heat (not ‘lost’ if used to maintain Tb) 1. Anabolic -creation, assembly, repair, growth (positive nitrogen balance) 2. Catabolic -energy release from complex molecules (carbos, fats, proteins) -energy storage in phosphate bonds (ATP) and metabolic intermediates (glucose, lactate) 12

13. Chemical Energy (16-1) 13

14. Metabolic Rate -measurable conversion of chemical energy into heat -used to understand: -energy budgets -dietary needs -body size implications -habitat effects -costs of various activities -mode of locomotion -cost of reproduction 14

15. Metabolic Rates -Basal Metabolic Rate, BMR -minimal environmental and physiological stress (appropriate ambient temperature, post-digestive, resting etc.) -Standard Metabolic Rate, SMR -similar to BMR, but at a given Tb -Field Metabolic Rate, FMR -average metabolic rate of animal in natural setting -hard to measure 15

16. Metabolic Rates Basal Metabolic Rate, BMR -important components: 1. Membrane form and function maintenance of electrochemical gradients -proton pumps in mitochondrial membranes -Na/K-ATPase pumps in plasma membrane 2. Protein synthesis 3. ATP formation 16

17. Specific Dynamic Action (SDA) -Metabolic Rate increases during digestion -2-3x resting metabolism in ectotherms Think about infrequently feeding snakes... (16-5) 17

18. Measuring Metabolism Direct Calorimetry -measure heat produced -known mass of water surrounding chamber -not often used (maybe for small birds, mammals) Indirect Calorimetry 1. Bomb calorimetry (food and waste) 2. Radioisotopes deuterium or tritium (H 3 ) labelled water oxygen radioisotopes (O 18 ) (doubly-labelled water) -measure loss of CO 2 and water over time -can be used in the field -measure metabolism and water flux 18 4kJ = 1kcal Power (W)= J/s

19. Measuring Metabolism Respirometry -measure O 2 consumption and CO 2 production -assumes primarily aerobic metabolism -closed vs. open 19 4kJ = 1kcal Power (W)= J/s

20. (16-3) gills lungs skin 20

21. R Q, Respiratory Quotient RQ =RQ = Rate of CO2 production Rate of O2 consumption Value depends on substrate oxidized: Energy Storage 21 4kJ = 1kcal Power (W)= J/s

22. R E, Respiratory Exchange Ratio R E = instantaneous ratio of O2 consumption and CO2 production (16-4) 22

23. Metabolic Scope Aerobic Metabolic Scope = max sustainable metabolic rate / BMR -usually measured as O2 consumption -often = 10-15 x BMR -does not include anaerobic contributions -best measured at steady-state, sustainable levels 23

24. Aerobic Scope Mammal MAS (max aerobic speed) 7.5x that of Lizard MAS (of similar body size) Anaerobic Scope Mammal and Lizard maximal speed equivalent at a given body mass -ecological implications? -both tend to increase with increasing body mass 24

25. (16-2) Oxygen Debt -repay anaerobic contribution to elevated metabolism -oxidize anaerobic products (e.g., lactate) 25

26. VO 2 Measurement - Before, during, and after exercise Thomas Hancock: data and slides Desert Iguana 26

27. VO 2 Time (min) 0 15 30 45 EXERCISE RECOVERY EPOC: Excess Post-exercise Oxygen Consumption Activity and Associated Oxygen Consumption EEOC: Excess Exercise Oxygen Consumption 27

28. VO 2 Time (min) 0 15 30 45 EXERCISE RECOVERY EPOC EEOC TEOC = Total Excess Oxygen Consumption = EEOC + EPOC Activity and Associated Oxygen Consumption 28

29. Muscle Lactate Exercise, 29

30. Energy Budget Implications Costs for Exercise and Recovery: - A Single Bout: 15 seconds at Maximum intensity Traditional Estimates: 0.7% of daily energy expenditure Inclusion of EPOC: 4.6% of daily energy expenditure 30

31. VO 2 Time (min) 31 Length of Bout is Important:

32. VO 2 Time (min) 32

33. VO 2 Time (min) 33

34. VO 2 Time (min) 34

35. VO 2 Time (min) EPOC is now a large fraction of the net metabolic expenditure. 35

36. Phylogenetic Effects FMR (kJ/day) (Nagy, Girard, Brown 1999) 100g mammal 100g reptile 100g bird 11.8 142 242 Energy Budgets… Ecological Role… 36

37. Scaling Effects Allometry - changes in body proportions as animals get larger (mouse vs. elephant) Metabolic Rate - mass-specific metabolic rate decreases with increasing body mass (16-6) linear squared cubed 37

38. 38 Knut Schmidt_Nielsen 1972 (a) = elephant freaked out and died (1960’s) -What is the correct dose? -Importance of Scaling! 0.1mg/kg 0.2mg for 70 kg

39. (16-8) 39

40. Scaling Power Functions: How do morphology and metabolism change with body mass? MR = aM b Metabolic rate Y-intercept (of log-log plot) Body mass Scaling exponent logMR = loga + b(logM) Can look at mass-specific rates by dividing through by M Take log of both sides (Linearizes) 40

41. (16-8) MR = aM b b = 0.75 (slope) logMR = loga + b(logM) 41

42. (16-7) 42

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