An enzyme is considered a(n) because it speeds up a chemical reaction without being used up. 2. in a catalyzed reaction, a reactant is often called a(n) . 3. an enzyme is specific because the shape of its matches only particular reactants. 4. an enzyme speeds up reactions by lowering the . 5. the between an active site and its substrate often strains bonds and the reaction proceed. 6. a(n) , which is often a vitamin, binds to an enzyme and plays a role in catalysis. 7. high temperatures or changes in ph can an enzyme, causing it to lose its shape and biological activity.