Case 4
Learning goals
How does the surface to volume ratio affect metabolism in different species?
The smaller the volume, the bigger the surface, the higher the metabolism
Small animals have a larger surface/volume ratio -> lose more heat to their
surroundings, thus need a higher BMR
BMR <-> mass0.78
Surface <-> volume0.63
There are endotherm and ectoderm animals, which differ in body temperature
o Endotherm: Constant body temperature, can be regulated by shivering
thermogenesis and sweating etc.
o Ectoderm: Depends on the temperature of the environment, eg. sun
What is the Harris and Benedict equation?
o Compare to Kleibers rule for inter species comparison
o Compare energy expenditure of adult male (80 kg) to pre puberty girl (40 kg)
The Harris-Benedict equation is used to estimate an individual’s BMR, based on sex, weight,
height and age
Men; BMR = 66.5 + (13.75 * weight in kg) + (5.003 * height in cm) - (6.75 * age)
Women; BMR = 655.1 + (9.563 * weight in kg) + (1.850 * height in cm) - (4.676 * age)
Being taller -> more surface -> more heat loss to surroundings -> more heat production ->
higher BMR
Women are smaller than men, thus lower heat production, thus lower BMR
An adult male is taller than a pre-puberty girl, thus he will have a higher BMR
Kleibers law: B = b*M0.75
B = basal metabolic rate
M = body mass
b = normalized constant
This means that BMR decreases with body mass increase
Basal cell mass
How does the difference in mitochondrial structure affect the metabolic rate?
o Relation to Fusion & Fission
Amount of mitochondria decrease when body size increases
Make ATP and produce heat
Basal unregulated: All tissues, always leakage
Inducible regulated:
Oxygen consumption: 80-90%
Learning goals
How does the surface to volume ratio affect metabolism in different species?
The smaller the volume, the bigger the surface, the higher the metabolism
Small animals have a larger surface/volume ratio -> lose more heat to their
surroundings, thus need a higher BMR
BMR <-> mass0.78
Surface <-> volume0.63
There are endotherm and ectoderm animals, which differ in body temperature
o Endotherm: Constant body temperature, can be regulated by shivering
thermogenesis and sweating etc.
o Ectoderm: Depends on the temperature of the environment, eg. sun
What is the Harris and Benedict equation?
o Compare to Kleibers rule for inter species comparison
o Compare energy expenditure of adult male (80 kg) to pre puberty girl (40 kg)
The Harris-Benedict equation is used to estimate an individual’s BMR, based on sex, weight,
height and age
Men; BMR = 66.5 + (13.75 * weight in kg) + (5.003 * height in cm) - (6.75 * age)
Women; BMR = 655.1 + (9.563 * weight in kg) + (1.850 * height in cm) - (4.676 * age)
Being taller -> more surface -> more heat loss to surroundings -> more heat production ->
higher BMR
Women are smaller than men, thus lower heat production, thus lower BMR
An adult male is taller than a pre-puberty girl, thus he will have a higher BMR
Kleibers law: B = b*M0.75
B = basal metabolic rate
M = body mass
b = normalized constant
This means that BMR decreases with body mass increase
Basal cell mass
How does the difference in mitochondrial structure affect the metabolic rate?
o Relation to Fusion & Fission
Amount of mitochondria decrease when body size increases
Make ATP and produce heat
Basal unregulated: All tissues, always leakage
Inducible regulated:
Oxygen consumption: 80-90%
