Whole-Animal Metabolism

Whole-Animal Metabolism

Animals require chemical energy for:• activity (muscular work)• synthetic activities• heat production (in endotherms)

How can we determine how much energy anorganism requires and uses for these activities?

Look at heat production:

Burn 1 mol (180g) of glucose in a calorimeter*:

1 mol glucose + 6 mol O2 6 mol CO2 + 6 mol H2O +686 kcal (heat)

Metabolize 1 mol of glucose aerobically in an animal:

1 mol glucose + 6 mol O2 + 38 mol ADP + 38 mol Pi 6 mol CO2 + 42 mol H2O + 38 mol ATP + 423 kcal heat

266 kcal

www.umr.edu/-gbert/animation.html

Eventually, all the chemical energy in theorganism will be released as heat -

regardless of the food source.

Therefore, Rate of heat production = Metabolic rate = Em

Holds for all organisms that are not growing

Again, assuming an organism is respiringaerobically, what alternative measures

might we use to approximate the metabolic rate?

Hint:

1 mol glucose + 6 mol O2 + 36 mol ADP + 36 mol Pi 6 mol CO2 + 42 mol H2O + 36 mol ATP + 423 kcal

Answer?

Oxygen consumption

Carbon dioxide expiration

Carbohydrates C6H12O6 + 6 O2 6 CO2 + 6 H2O

Ratio of CO2 prod. / O2 consumed = respiratory quotient = R.Q.

Fat 2 C51H98O6 + 145 O2 102 CO2 + 98 H2O

R.Q. = 102 CO2 / 145 O2 = 0.70

ProteinR.Q. = 0.80

R.Q. = 6 CO2/ 6 O2 = 1.00

Oxygen/carbon dioxide relationships

1 Joule = 0.239 cal

Kcal/liter O2______

5.0 4.7

4.5

if you wish, you can use 4.8 kcal • l O2-1)

Assumes a mixed diet

• size• temperature & season• hibernation & torpor• salinity• photoperiod & tidal cycle• pressure of oxygen• activity

Numerous physical and behavioral factorsaffect metabolic rate:

Definitions:

Basal metabolic rate (BMR) - minimal rate of metabolism

for a fasting, inactive individual (with no heat prod.for homeotherm).

Standard metabolic rate (SMR) - rate for an individualat rest at a given temperature.

Active metabolic rate (AMR) - rate for forced, maximalactivity at a given temperature.

Activity vs. VO2

•

Locomotion is expensive:

In humans, VO2 can increase 15-20 X during exercise

In insects, VO2 can increase 50-200 X during flight:•

activity (e.g. swimming speed)

VO2’•

SMR

Metabolic Scope for Activity = AMR / SMR

Goldfish (ml O2 • kg-1 • h-1)

280

40

VO2’•

Temp. (°C)

0 40

AMR

SMR

Expressed as dimensionless value (e.g., 8)

Cost of Locomotion

VO2 liters O2 • kg-1 • h-1

C.L. = = = liters O2 • kg-1 • km-1

velocity km • h-1

•

C.L.

Salmon

velocity (lengths • s-1)0 1 2 3 4

C.L.

Body Mass (kg)

0.1 1 10 100 1000 10000

runningflying

swimming