What is the primary nutrient class responsible for storing energy in animals?

The primary nutrient class responsible for storing energy in animals is lipids. Lipids, which include fats and oils, are highly efficient energy storage molecules due to their high caloric content. When compared to carbohydrates and proteins, lipids provide more than double the amount of energy per gram. This energy is stored in the form of triglycerides, which can be mobilized when the animal requires energy reserves during periods of fasting, exercise, or other metabolic demands.

Lipids play a critical role not just in energy storage but also in supporting cellular structure, insulating and protecting organs, and facilitating the absorption of fat-soluble vitamins. While carbohydrates are also an important energy source, their energy storage capacity is more limited in comparison to lipids. Proteins serve primarily as building blocks for tissues, enzymes, and hormones, rather than as a primary form of energy storage. Vitamins are essential micronutrients necessary for various metabolic functions but do not serve as energy storage molecules.