NUTR 3210 Lecture Notes - Lecture 3: Calorimeter, Cellular Respiration, Energy Economics
27 Jun 2018
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What is energy?
oEnergy is the capacity to do metabolic or physical work
oEnergy is provided to the body in the diet, in the form of food or drinks that
contain macronutrients
oBody energy is also expended as macronutrients are metabolized
oCellular energy is measured as ATP
oFood energy is measured as calories
Measure of the amount of energy needed to raise the temperature of
1g of water by 1C
Cal = Calorie of kcal, which is equal to 1000 calories, and is the amount
of energy needed to raise the temperature of 1kg of water by 1C
oThe joule is another measurement of food energy, but isn't used widely
oCan consider energy intake from the diet, as well as energy expenditure by the
body
Energy balance
oCan be determined from the difference between energy intake and energy
expenditure
oIf energy balance is neutral, energy intake is equal to energy expenditure
This should result in maintenance of body weight
oIf energy balance is positive, energy intake is greater than energy expenditure
This is norming during growth, development, and pregnancy, but in
adulthood, will result in weight gain
oIf energy balance is negative, energy intake is less than energy expenditure
Also known as protein/ calorie malnutrition
This is normal during an infection, but will result in weight loss
oExercise can induce positive or negative energy balance
Positive balance is when body mass (usually lean) accumulates
Negative balance is when body mass (usually adipose) accumulates
Energy and combustion
oCombustion of an organic substance is a process whereby a fuel reacts with
oxygen and gives off heat, carbon dioxide, and water -> the level of combustion relates
to the amount of energy in the fuel
oCombustion can occur externally (outside the body); this is what happens when
we burn a sample of food in a bomb calorimeter
oCombustion can also occur internally (inside the body); this is what happens
when we oxidize food in the process of metabolism (cellular respiration)
oKey point: the burning of fuel in a high oxygen environment (such as our
atmosphere) is essentially the same as the oxidation of fuel in our bodies, and both
produce carbon dioxide, water and heat
Fuel combustion and metabolism
oIn metabolism (cellular respiration), some heat (~60%) is lost as body heat, while
~40% is temporarily captured as ATP. As the body does subsequent work, the ATP is
used in heat releasing processes. The total heat produced in fuel combustion and
cellular respiration will be the same
Bomb calorimetry
oBomb calorimetry is essentially combustion - a sample of food is combusted in a
high oxygen environment and heat is produced. The amount of heat is related to the
energy in the food. The caloric content of the food can be determined by measuring the
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Document Summary
Energy is the capacity to do metabolic or physical work. Energy is provided to the body in the diet, in the form of food or drinks that contain macronutrients o o o o o. Body energy is also expended as macronutrients are metabolized. Measure of the amount of energy needed to raise the temperature of. Cal = calorie of kcal, which is equal to 1000 calories, and is the amount of energy needed to raise the temperature of 1kg of water by 1c. The joule is another measurement of food energy, but isn"t used widely. Can consider energy intake from the diet, as well as energy expenditure by the body. Can be determined from the difference between energy intake and energy expenditure o o o o. If energy balance is neutral, energy intake is equal to energy expenditure. This should result in maintenance of body weight. If energy balance is positive, energy intake is greater than energy expenditure.
