Lee and Marisol are conducting a science experiment to identify different kinds of macromolecules in food. They prepare the following table to help them remember the chemical reactions that indicate the presence of each type of macromolecule they are studying. Substance Reaction If Present Sugar blue Benedict's solution turns green, yellow, or orange Starch brown iodine turns purple Protein blue Biuret solution turns pink or purple Lipids colorless Sudan stain turns red Suppose that one of the substances they are testing turns bright red when they add a few drops of Sudan stain. What is the basic molecular structure of the substance?