Which of the following statements about enzymes is true?
Multiple Choice
Enzymes lower the energy of the transition state for the rate-determining step.
Enzymes Increase the activation energy for a reaction.
Enzymes shift the equilibrium to favor the product.
Enzymes decrease the equlilibrium constant.
The correct answer and explanation is:
The correct answer is: Enzymes lower the energy of the transition state for the rate-determining step.
Explanation:
Enzymes are biological catalysts that accelerate chemical reactions in living organisms by lowering the activation energy required for a reaction to occur. The activation energy is the energy required to initiate a chemical reaction, and enzymes specifically lower this energy by stabilizing the transition state, which is the high-energy, unstable intermediate state that occurs as reactants are converted into products.
The transition state is the point where the reactants are in the process of being transformed into products. Enzymes work by providing an alternative reaction pathway that has a lower activation energy. This means that a greater proportion of molecules will have sufficient energy to overcome the activation barrier, thus speeding up the reaction.
The statement “Enzymes increase the activation energy for a reaction” is incorrect. Enzymes do not increase the activation energy; they lower it, which is their primary role in catalysis.
The statement “Enzymes shift the equilibrium to favor the product” is also incorrect. Enzymes do not change the equilibrium position of a reaction. They only speed up the rate at which equilibrium is reached, but they do not alter the concentrations of reactants and products at equilibrium. This is because enzymes do not affect the free energy change (ΔG) of the reaction.
Lastly, the statement “Enzymes decrease the equilibrium constant” is incorrect. The equilibrium constant is determined by the free energy change of the reaction and is not affected by enzymes. Enzymes only affect the rate of the reaction, not the overall thermodynamic properties such as equilibrium.
In summary, enzymes are essential for speeding up reactions by lowering the energy required to reach the transition state, thus facilitating the process without altering the overall equilibrium of the reaction.