Final answer:
Enzymes primarily affect the reaction rate but can also affect how a reaction approaches equilibrium, and are capable of finer control when two different enzymes catalyze reversible reactions in opposite directions. They are not consumed by the reaction and do not change the overall free energy change (ΔG) of the reaction, allowing them to catalyze multiple reactions over time.
Step-by-step explanation:
The statement that in reactions catalyzed by enzymes, only the rate of the reaction changes is not entirely accurate. Enzymes do indeed primarily affect the reaction rate, but they also exhibit other influences on the reaction system. When an enzyme catalyzes a reaction, it binds to a specific substrate to form an enzyme-substrate complex, facilitating the reaction without being consumed in the process. The concentration of enzymes and substrates can influence the rate at which a reaction approaches equilibrium; for instance, with an excess of substrate, further increases in its concentration will not affect the reaction rate since all the enzyme binding sites will already be occupied.
Moreover, some biochemical reactions are controlled by two different enzymes, each specific for one direction of a reversible reaction. This adds an additional layer of regulation to the system, as it prevents the reaction from reaching equilibrium too quickly and allows finer control over the reaction rate. In cases where there is only one enzyme, the reaction can go to equilibrium, potentially stalling the process.
It is important to note that while enzymes accelerate reactions by decreasing the energy barrier (they do not change the overall ΔG of the reaction), they are unaffected by the reaction themselves. After catalyzing a reaction, an enzyme will release the product and remain available to catalyze further reactions.