Hank explains that biological molecules are essential sources of energy. They are used for energy storage and are the instructions that help organisms grow. Biological molecules are found in carbohydrates, lipids, and proteins. Hank uses biological molecules to explain why humans don't eat grass and how humans get energy from bread.

Key Words: Sugars, Monosaccharides, Glucose, Fructose, Disaccharides, Sucrose, Polysaccharides, Cellulose, Glycogen