You can think of a coenzyme or cosubstrate as a helper molecule that aids an enzyme in catalyzing a chemical reaction. A coenzyme requires the presence of an enzyme in order to function. It is not active on its own. While enzymes are proteins, coenzymes are small, nonprotein molecules. Coenzyme Q10 (CoQ10) is a nutrient your body makes naturally. It’s also in many foods. CoQ10 acts as an antioxidant, which protects cells from damage and plays an important part in your. coenzyme, Any of a number of freely diffusing organic compounds that function as cofactor s with enzyme s in promoting a variety of metabolic reactions. Unlike the enzyme, which emerges unchanged, the coenzyme undergoes a chemical change, accepting or donating the transported group. This action allows the enzyme to execute chemistry that the protein’s amino acid structure cannot accomplish on its own. A coenzyme functions by acting as a temporary carrier, shuttling specific chemical groups, electrons, or hydrogen atoms between molecules during a reaction. This transfer mechanism allows enzymes to transform starting materials, known as substrates, into the desired end products. A cofactor can be either an inorganic ion, such as Zn 2+, or a small organic molecule, called a coenzyme. A coenzyme is not a catalyst but is a reactant that undergoes chemical change during the reaction and requires an additional step to return to its initial state. Coenzyme Q10, also called CoQ10, supplements might be helpful for treating conditions such as congestive heart failure and preventing migraines. Most healthcare professionals think CoQ10 is safe, with few side effects. Image Credit: Explode / Shutterstock.com What are coenzymes? A coenzyme is defined as an organic molecule that binds to the active sites of certain enzymes to assist in the catalysis of a. A coenzyme is an organic non-protein compound that binds with an enzyme to catalyze a reaction. Coenzymes are often broadly called cofactors, but they are chemically different. Coenzyme A (CoA, SHCoA, CoASH) is a coenzyme, notable for its role in the synthesis and oxidation of fatty acids, and the oxidation of pyruvate in the citric acid cycle.