Which of the following is NOT a characteristic of lipids?

Lipids are a diverse group of organic compounds that share a common characteristic of being hydrophobic, meaning they do not dissolve in water. This trait is fundamental to their function and purpose within biological systems. When considering the other options, lipids indeed play a crucial role in multiple biological functions.

Lipids are important components of cell membranes, primarily in the form of phospholipids, which help maintain membrane integrity and fluidity. They are also pivotal for storing energy; triglycerides, for example, are a primary form of energy storage in animals due to their high energy content. Additionally, certain lipids function as signaling molecules, which can initiate a variety of cellular processes, including hormone signaling and regulating inflammation.

Thus, it is accurate to state that being soluble in water is not a characteristic of lipids, as this property directly contradicts their fundamental nature.