Multiple Choice
What form of energy is stored in food?
8. Thermochemistry
Nature of Energy
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Which energy substrate contains the most energy per gram?
A
Proteins
B
Carbohydrates
C
Fats
D
Nucleic acids
Verified step by step guidance1
Understand that energy substrates are molecules that provide energy when metabolized. The main energy substrates in biological systems are carbohydrates, proteins, fats, and nucleic acids.
Recognize that the energy content of these substrates is measured in kilocalories (kcal) per gram. This is a measure of how much energy is released when the substrate is completely oxidized in the body.
Recall that carbohydrates and proteins both provide approximately 4 kcal per gram. This is because they have similar structures and energy content when metabolized.
Understand that fats provide approximately 9 kcal per gram, which is more than double the energy content of carbohydrates and proteins. This is due to the higher number of carbon-hydrogen bonds in fats, which release more energy when broken.
Note that nucleic acids are not typically used as a primary energy source in the body, and their energy content is not usually considered in this context. Therefore, fats contain the most energy per gram among the common energy substrates.
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