Transcript Chapter 13

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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
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 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)
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(15-37)
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
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Lipids
ER
Golgi
Lacteal
(15-38)
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
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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+
facilitate water reabsorption
(Cl- follows)
to
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Secretions etc.
ileum
(15-39)
=
Nutritional Requirements…
(Essential?)
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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)
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 function
maintenance 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
(16-5)
Think about infrequently feeding snakes...
Measuring Metabolism
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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)
4kJ = 1kcal
Power (W)=
J/s
2. Radioisotopes
deuterium or tritium (H3) labelled water
oxygen radioisotopes (O18)
(doubly-labelled water)
-measure loss of CO2 and water over time
-can be used in the field
-measure metabolism and water flux
Measuring Metabolism
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Respirometry
-measure O2 consumption and CO2 production
-assumes primarily aerobic metabolism
-closed vs. open
4kJ = 1kcal
Power (W)=
J/s
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lungs
gills
skin
(16-3)
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RQ, Respiratory Quotient
Rate of CO2 production
RQ =
Rate of O2 consumption
Value depends on substrate oxidized:
Energy
Storage
4kJ = 1kcal
Power (W)=
J/s
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RE, Respiratory Exchange Ratio
RE = instantaneous ratio of
O2 consumption and CO2 production
(16-4)
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 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
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Oxygen Debt
-repay anaerobic contribution to elevated metabolism
-oxidize anaerobic products (e.g., lactate)
(16-2)
VO2 Measurement - Before, during, and after exercise
Desert Iguana
Thomas Hancock:
data and slides
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Activity and Associated Oxygen Consumption
EPOC:
Excess
Post-exercise
Oxygen
Consumption
VO2
EEOC: Excess Exercise
Oxygen Consumption
EXERCISE
0
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RECOVERY
30
Time (min)
45
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Activity and Associated Oxygen Consumption
TEOC = Total Excess Oxygen Consumption
= EEOC + EPOC
EEOC
VO2
EPOC
EXERCISE
0
15
RECOVERY
30
Time (min)
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Muscle Lactate
Gas tr ocne m ius
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Lactate (mM)
RIF
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WIF
30
20
10
0
0
Exercise,
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4
6
60
8 10 12 14 16
Recovery Time (min)
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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
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VO2
Length of Bout is Important:
Time (min)
VO2
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Time (min)
VO2
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Time (min)
VO2
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Time (min)
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VO2
EPOC is now a large
fraction of the net
metabolic expenditure.
Time (min)
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Phylogenetic Effects
FMR (kJ/day)
100g reptile
11.8
100g mammal
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100g bird
242
(Nagy, Girard, Brown 1999)
Energy Budgets…
Ecological Role…
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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
cubed
squared
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Knut Schmidt_Nielsen 1972
0.1mg/kg
0.2mg for 70 kg
(a) = elephant freaked out and died (1960’s)
-What is the correct dose?
-Importance of Scaling!
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(16-8)
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Scaling
How do morphology and metabolism change with
body mass?
Body
mass
Power Functions:
Scaling exponent
MR = aMb
Take log
of both
sides
Metabolic
rate
Y-intercept
logMR = loga + b(logM)
(of log-log plot)
(Linearizes)
Can look at mass-specific rates by dividing through by M
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(16-8)
MR = aMb
logMR = loga + b(logM)
b = 0.75
(slope)
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(16-7)
xx
END