Question

Think about where the shared electrons are located in polar and non-polar bonds relative to the nuclei of the atoms, and how that might relate to the amount of potential energy stored in these bonds. Based on this information about bonds and electronegativity, explain how fats contain more energy than carbohydrates

Answer 1

1) The energy stored in the bonds of any fat based molecule, or lipid, is greater than that of a carbohydrate molecule. Simple carbohydrates are easily broken down for quick bursts of energy, while complex carbohydrates take longer to break down.

2) Fats on the other hand, are all more difficult to digest because of the size of their molecules and the complexity of their structure. Fats are also stored more rapidly; they are the body's emergency power source. Fat has 2.25X more energy than Carbohydrates.

3)fats are made up of fatty acids and glycerol. When they are broken down, they produce more energy than that produced by carbohydrates.

4) The reason for this is the amount of oxidation that takes place as these compounds are converted to carbon dioxide and water. Carbon for carbon, fats require more oxidation to become CO₂and H2O than do carbohydrates.

5 ) Roughly speaking, carbohydrates already have one oxygen for every carbon atom, thus, each carbon atom needs only one more oxygen and each pair of hydrogen atoms needs one more oxygen.

6)However, almost every carbon atom in a fat molecule needs two oxygens instead of just one additional one, and each pair of hydrogen atoms still needs one more oxygen. So, just from counting the number of oxygens needed to be added, fats require about half again as much oxygen for the same number of carbon atoms. Because of this, the oxidation of fats takes longer, but it also gives off more energy.

7)When comparing gram to gram, instead of carbon to carbon, the effect is exaggerated. When you weigh a carbohydrate, more oxygen is included in that weight. When you weigh a fat, you get more carbon atoms per gram and therefore, gram for gram, the fats will give even more energy (over twice as much) than will the carbohydrates.

8 )Generally, fats provide about 9 kilocalories per gram and carbohydrates provide about 4 kilocalories per gram. (Using nutritional units, that is 9 Calories/gram for fats and 4 Calories/gram for carbohydrates.)