Origin of Chordates BIOL 495 – Chapter Two. Comparative Vertebrate Anatomy.
Lecture 25, 02 Dec 2003 Chapter 15, Feeding and Digestion Chapter 16, Energy Expenditure, Body Size...
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Transcript of Lecture 25, 02 Dec 2003 Chapter 15, Feeding and Digestion Chapter 16, Energy Expenditure, Body Size...
Lecture 25, 02 Dec 2003Chapter 15, Feeding and Digestion
Chapter 16, Energy Expenditure, Body Size
Vertebrate PhysiologyECOL 437
University of ArizonaFall 2003
instr: Kevin Boninet.a.: Bret Pasch
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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)
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ABSORPTION:
-Across epithelium of brush border (microvilli)-Glycocalyx has enzymes for final cleavage disaccharidases, aminopeptidases, phosphatases-Simple Diffusion
1 fat-soluble substances2 small water soluble substances through
regulated aquaporins3 down concentration or electrochemical
gradients-Facilitated Diffusion
1 monosaccharides and amino acids2 transporter proteins3 down conc. gradient or4 coupled to Na+ gradient (Na/K-
ATPase)
3
(15-37)
4
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
(15-38)
Lipids6
ER
Golgi
Lacteal
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
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
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(15-39)
Secretions etc.
=
9
ileum
Nu
trit
ional R
eq
uir
em
ents
… (
Ess
enti
al?
)
10
Chapter 16
Energy Expenditure-temperature-size-activity
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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)
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Chemical Energy
(16-1)
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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
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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
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Metabolic Rates
Basal Metabolic Rate, BMR-important components:
1. Membrane form and functionmaintenance of electrochemical gradients-proton pumps in mitochondrial membranes-Na/K-ATPase pumps in plasma membrane
2. Protein synthesis
3. ATP formation
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Specific Dynamic Action (SDA)
-Metabolic Rate increases during digestion-2-3x resting metabolism in ectotherms
Think about infrequently feeding snakes...
(16-5)
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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. Radioisotopesdeuterium or tritium (H3) labelled wateroxygen radioisotopes (O18)(doubly-labelled water)
-measure loss of CO2 and water over time-can be used in the field-measure metabolism and water flux
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4kJ = 1kcal
Power (W)=J/s
Measuring Metabolism
Respirometry-measure O2 consumption and CO2
production-assumes primarily aerobic metabolism-closed vs. open
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4kJ = 1kcal
Power (W)=J/s
(16-3)
gills
lungs
skin
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RQ, Respiratory Quotient
RQ = Rate of CO2 production
Rate of O2 consumption
Value depends on substrate oxidized:
Energy Storage
21
4kJ = 1kcal
Power (W)=J/s
RE, Respiratory Exchange Ratio
RE = instantaneous ratio of O2 consumption and CO2 production
(16-4)
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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
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Aerobic ScopeMammal MAS (max aerobic speed)
7.5x that of Lizard MAS (of similar body size)
Anaerobic ScopeMammal and Lizard maximal speed
equivalent at a given body mass
-ecological implications?
-both tend to increase with increasing body mass
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(16-2)
Oxygen Debt-repay anaerobic contribution to elevated
metabolism-oxidize anaerobic products (e.g., lactate)
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VO2 Measurement - Before, during, and after exercise
Thomas Hancock: data and slides
Desert Iguana
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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
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VO
2
Time (min)
0 15 30 45
EXERCISE RECOVERY
EPOC
EEOC
TEOC = Total Excess Oxygen Consumption = EEOC + EPOC
Activity and Associated Oxygen Consumption28
Muscle Lactate
0
10
20
30
40
50
Lac
tate
(m
M)
0 2 4 6 8 10 12 14 16
Recovery Time (min)
WIF
RIF
Gastrocnemius
60
Exercise,
29
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
VO
2
Time (min)
31
Length of Bout is Important:
VO
2
Time (min)
32
VO
2
Time (min)
33
VO
2
Time (min)
34
VO
2
Time (min)
EPOC is now a large fraction of the net metabolic expenditure.
35
Phylogenetic Effects
FMR (kJ/day)
(Nagy, Girard, Brown 1999)
100g mammal
100g reptile
100g bird
11.8
142
242
Energy Budgets…Ecological Role…
36
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
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
(16-8)
39
Scaling
Power Functions:
How do morphology and metabolism change with body mass?
MR = aMb
Metabolicrate
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
(16-8)
MR = aMbb = 0.75(slope) logMR = loga +
b(logM)
41
(16-7)
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END
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