The human body can get energy by metabolizing proteins, carbohydrates or fatty acids, depending on the circumstances. Roughly speaking, the energy it gets comes mostly from allowing all the carbon atoms in the food molecules to become oxidized to carbon dioxide by reaction with oxygen from the atmosphere. Hence the energy content of food is roughly proportional to the carbon content.

Let's consider alanine , one of the amino acids from which proteins are made, and palmitic acid , a fatty acid from which fats are made. Using the idea above about energy content, calculate the ratio of the energy the body gets metabolizing each gram of alanine to the energy the body gets metabolizing each gram of palmitic acid.