What macromolecules are used for energy?
The human body has three macromolecule energy sources:
carbohydrates, lipids, and proteins. Carbohydrates are made up of
many individual sugar units which are linked together in long
chains. The chains can be straight, or they can be branched.
Carbohydrates have the molecular formula C6nH(10n+2)O(5n+1) so they
only contain carbon, oxygen, and hydrogen. Sugars are used for
short to intermediate term storage of energy. That's why drinking a
sugary drink can give you energy (a sugar rush) for a short time
but then it wears off. The amount of energy in sugar is 4
kcal/g.Proteins are usually made of straight chains of linked
peptide units. They provide long term energy storage. Proteins
contain carbon, oxygen, hydrogen, and nitrogen with small amounts
of sulfur with varying molecular formulas. That is why eating a
steak will make you feel full for many hours. Proteins are also
used to build up many of the structures in the human body so they
are necessary to repair damaged tissue. The amount of energy in
protein is 4 kcal/g, just like sugar.Fats are made of up clusters
of fatty acids, long chains of repeating CH2 units so they are
mostly made of just carbon and hydrogen. Fats are used for long
term energy storage. Excess sugar and protein that is consumed by
most animals are converted to fats to save the energy for later.
The amount of energy in fat is very high, 9kcal/g.
