Which statement about enzymes is true? they lower the free energy of the products. they are not permanently altered by the reactions they catalyze. each catalyzes reactions of a broad range of substrates. they are only rarely regulated. they catalyze reactions by raising activation energy.

They are not permanently altered by the reaction they catalyze.

Explanation: Enzymes are usually in lower concentration than substrate molecules they catalyze. Hence an enzyme catalyzes as many substrate molecules as it can. So when an enzyme binds a substrate to it's active site, it does this so as to increase the reaction rate which otherwise would not have been possible without the enzyme. It doesn't mean that the enzyme itself takes part in the chemical reaction. Hence, once an ES(Enzyme-substrate) moves to P(product), the product leaves the active site and the enzyme returns to it's original confirmation ready for binding another molecule of the substrate. Therefore, the enzyme is altered transiently in order to allow the substrate fit into it's active site. Its never altered permanently