Question

if a cell needs to store energy for a long period, which macromolecule would it primarily use and why?
carbohydrates, because they store more energy.
proteins, because they are structural.
nucleic acids, because they store genetic information.
lipids, because they store more energy per gram

Explanation:

The question is about which macromolecule a cell would primarily use to store energy for a long period. Lipids (like fats and oils) are known to store more energy per gram compared to carbohydrates, proteins, or nucleic acids. Carbohydrates are for short - term energy, proteins are structural/functional, and nucleic acids store genetic info. So lipids are best for long - term energy storage because they have a higher energy density (more energy per gram).

Answer:

Lipids, because they store more energy per gram.