Organic compounds contain carbon and are the building blocks of living things. They include carbohydrates, lipids, proteins, and nucleic acids. Carbohydrates like starch and cellulose are made of sugars and function to store energy. Lipids such as fats and oils contain mostly carbon and hydrogen, function to store long-term energy and provide insulation. Proteins are made of amino acids and are essential for cellular functions. Nucleic acids DNA and RNA carry genetic codes and instructions for protein synthesis. These macromolecules are polymers of smaller monomers that link through condensation reactions.