The relative energy storage of biological macromolecules varies by type:
- Lipids store the most energy per gram, roughly twice the energy of carbohydrates and proteins. This makes lipids the primary long-term energy storage molecules in animals, stored as fat (triacylglycerols).
- Carbohydrates provide energy but less than lipids per gram. They are stored as glycogen in animals and starch in plants. Glycogen is branched for rapid mobilization of glucose for short-term energy needs.
- Proteins can be used for energy but are primarily structural and functional molecules. Their energy storage capacity is less than carbohydrates and lipids.
- Nucleic acids are not significant energy storage molecules [general knowledge].
In summary, lipids > carbohydrates > proteins in terms of relative energy storage capacity. Lipids are favored for long-term energy storage due to their higher caloric content and lower associated water weight compared to carbohydrates.
