Enzymes act as catalysts in the chemical reactions in cells. A catalyst is a molecule which increases the rate of a reaction but is not the substrate or product of that reaction. A substrate is a molecule upon which an enzyme acts to yield a product. Enzymes are usually named for the substrate on which they act or the action which they perform. They are important metabolically.
Sugars are the major energy storage molecules for living organisms.
Simple sugars are known as monosaccharides . Glucose Fructose Sugars composed of two simple sugars are known as disaccharides . Complex carbohydrates are made by combining more and more simple sugars. Lipids Lipids are characterized by their solubility in organic solvents rather than in water. The structure of lipids shows no common features throughout the class, although the structures tend to have more carbon-hydrogen bonds than any other class of biological molecules.