Which of the following statements best characterizes lipids?

Lipids are organic compounds that play crucial roles in biological systems, primarily characterized by their composition and properties. They are mostly composed of carbon and hydrogen atoms, which contribute to their hydrophobic nature—meaning they do not mix well with water. This unique structure allows lipids to function effectively in various biological roles, such as making up the cell membrane, storing energy, and serving as signaling molecules.

The other options do not accurately depict the nature of lipids. For instance, amino acids are the building blocks of proteins, not lipids. Additionally, while genetics is primarily governed by nucleic acids like DNA and RNA, lipids do not serve this function. Lastly, lipids are generally insoluble in water; their hydrophobic nature allows them to form barriers in cellular structures rather than dissolving in an aqueous environment. Therefore, the statement that lipids are composed primarily of carbon and hydrogen is the most accurate characterization of them.