Maintenance, growth,
reproduction, activity
Energy
Food/fuel is oxidized to form ATP
Metabolism =
Metabolic Rate =
1. Direct measure of heat production
= “direct calorimetry”
Lavoisier & Laplace
79.9 cal melts 1 g ice
(335 Joules)
2. Indirect measure of MR
Complete oxidation of 1 mol glucose:
Fuel + 6O2
(C6H12O6)
6CO2 + 6H2O + 2820 kJ
•Amount of energy ingested, O2 consumed, or CO2
produced is directly related to amount of heat produced
•BUT, heat production varies with foodstuff being
oxidized…
BUT, heat production varies with
foodstuff being oxidized…
HEAT PRODUCTION (KJ)
Per gram
of food
Per liter of O2
consumed
Per liter of CO2
produced
carbohydrates
17.1
21.1
21.1
lipids
38.9
19.8
27.9
Proteins (urea)
17.6
18.7
23.3
Relatively constant, but not exact…
Measuring O2 consumption:
Closed system respirometry:
Volume =
Initial O2 =
Final O2 =
(1 hour)
How can we measure FMR?
(measuring MR during activity)
How can we measure FMR?
Doubly labeled water:




dual isotope technique
can use with free-ranging terrestrial animals
no equipment attached to animal
measures CO2 production
O
H
18O
H
(Water)
H
3H
(Doubly-labeled water)
isotope in body
Doubly-labeled water
Initial sample
3H
Final sample
18O
time
Convert to estimates of CO2 production…
What factors affect an animal’s
metabolic rate?
1. Activity
What factors affect an animal’s
metabolic rate?
2. Digestion: “specific dynamic action”
1.4 kJ meal
5.6 kJ meal
What factors affect an animal’s
metabolic rate?
4. Reproductive Status
• Humans:
MR increases 30% near term
-growth of fetus
-fetal metabolic requirements
-growth of mammary tissue
• Golden-mantled ground squirrels:
- lactation takes up 1/3 of yearly energy budget!
What factors affect an animal’s
metabolic rate?
Many animals lower MR well below resting levels
5. Hibernation, Estivation,Torpor
6. Endothermy vs. Ectothermy
6. Endothermy vs. Ectothermy
physiological correlates of
huge MR difference
1. Higher SA/V in lungs; complex, efficient heart
2. Mitochondrial membrane SA ~4-5X bigger
3. Greater enzyme activity
6. Endothermy vs. Ectothermy
What does measuring O2
consumption tell us?
Endotherms:
Ectotherms:
basic metabolism
basic metabolism
thermoregulation
digestion
digestion
activity
activity
 reproduction/growth
 reproduction/growth
7. Temperature affects MR
ectotherms
endotherms
MR
MR
temperature
temperature
Metabolic Rate Summary
• What is MR and how can you measure it?
–
–
–
–
Direct Colorimetry (heat production)
Food Consumption
Oxygen Consumption
Carbon Dioxide Production
• Field metabolic rate
• Factors affecting metabolic rate:
–
–
–
–
–
–
–
Activity
Digestion
Starvation
Reproductive Status
Hibernation, Estivation, Torpor
Endothermy vs. Ectothermy
Temperature