National League for Nursing (NLN) Science Practice Exam

Which chemical structure is primarily involved in energy storage in living organisms?

1. Proteins

2. Nucleic acids

3. Carbohydrates

4. Lipids

The correct answer is: Lipids

Lipids are primarily involved in energy storage in living organisms due to their biochemical structure and properties. They are composed mainly of long hydrocarbon chains or rings, making them highly efficient for storing energy. When fats (a common form of lipids) are metabolized, they release a significant amount of energy compared to carbohydrates and proteins. Lipids, particularly triglycerides (which consist of glycerol and three fatty acids), can be stored in adipose tissue and serve as a dense energy reserve. The energy stored in lipids is utilized during periods of energy deficit, such as fasting or prolonged exercise, providing a sustained energy source that supports various biological activities. While carbohydrates do play a role in energy storage, primarily in the form of glycogen in animals and starch in plants, they are not as efficient in long-term energy storage compared to lipids. Proteins and nucleic acids, although essential for many cellular functions, do not primarily serve the purpose of energy storage, as their roles are more focused on structural and functional aspects of cells.