Which of the following statements is true about lipids?

Lipids serve several important functions in biological systems, with one of their primary roles being energy storage. They contain long hydrocarbon chains that are rich in carbon-hydrogen bonds, which store a significant amount of energy. When metabolized, lipids provide more than double the energy per gram compared to carbohydrates and proteins. This characteristic makes them an efficient form of energy storage in living organisms.

Additionally, lipids play crucial roles in forming cellular membranes, signaling molecules, and insulation, but their ability to store energy is particularly noteworthy. This is why the statement about lipids being primarily energy storage molecules is true; they are designed to be stored in the body and released when energy is required, especially during long-term activities or periods of fasting.

In contrast, the other statements do not accurately describe lipids. Lipids are typically nonpolar and hydrophobic, making them insoluble in water, which is contrary to the second statement. While certain lipids can be involved in cellular signaling and reactions, they cannot be directly converted into proteins, which are composed of amino acids. Thus, the notion of easy conversion to proteins does not hold true. Lastly, lipids are not all polar; in fact, many lipids are largely nonpolar, contributing