Chp 6 Energy Metabolism. Energy metabolism: - Catabolism: processes breaking down organic molecules to release energy - Anabolism: processes using energy to construct molecules Why animals need energy?. Energy is needed for work
- Catabolism: processes breaking down organic molecules to release energy
- Anabolism: processes using energy to construct molecules
Why animals need energy?
Animals can use chemical, electrical and mechanical energies (high grade energy) for work but not thermal energy (low grade energy).
Efficiency of energy transformation = output/input of high-grade
Efficiency: Always less than 1.
Ex: glucose 70%ATP + 30% heatFundamentals of Animal Energetics
Allows to estimate the kind of food that has been burned
Because this is cumbersome to calculate, the number 20.2J/ml O2 is used to calculate the MR from O2 consumption
Time of the day
For aquatic animal, the salinity of ambient water
The food effect: specific dynamic action (SDA) = calorigenic effect of ingested food, especially proteins
The SDA is about 25%-30% of the energy value of the meal.Factors that affect metabolic rates
The number of mitochondria per cells is higher in smaller species
Smaller species have also a more extensive respiratory tubes and circulatory vesselsMetabolic rate, size and activity
Weight-specific metabolic rate: relationship constant through homeo and poikilotherms (allometric relationship)
M = aWb
b = 0.65-0.75
a varies with groupsRelationship between size and metabolic rate
However, smaller bodies have a higher MR
How to provide the body with enough O2 to sustain a more intense MR?
By having an increased Heart Rate and an increased Respiratory Rate
Smaller species need more food per unit of body weight
Smaller species draw more resources from the ecosystem
Smaller species accumulate more toxins than larger one.Heart size and Heart ?
Energy absorption efficiency = absorbed/ingested energy
Growth growth efficiency= chemical-bondd energy of tissue added by growth (net)/ingested energy
Net growth efficiency = chemical-bond energy of tissue added by growth (net)/absorbed energy
Growth efficiency declines with ageEnergetics of food and growth
Afterward, there is a decrease in the investment
All life processes cost energy
Mental effort costs some, however, brain maintenance is overall costlyPractical consequences