Question

Students see the graph below in a textbook and are discussing it.

Students cannot decide which line shows an enzyme-catalyzed reaction.

Which evidence from the graph should the students use to make their decision?

Question 3 options:

Line B is lower than line A and indicates that less energy of activation is used to begin the reaction.


The lines are parallel to each other indicating the same amount of energy is being used in both reactions.


Line A is higher than line B and indicates that more energy of activation is used to begin the reaction.


The lines do not overlap each other indicating that the reaction is the same with and without an enzyme.

Answer 1

To determine which line shows an enzyme-catalyzed reaction in the context of a graph depicting reaction energy profiles, students should consider the concept of activation energy. Enzymes lower the activation energy required for a reaction to proceed.

In this case, the best evidence for identifying which line represents the enzyme-catalyzed reaction is:

**Line A is higher than line B and indicates that more energy of activation is used to begin the reaction.**

This statement indicates that Line B, which is lower, corresponds to the reaction with an enzyme, because enzymes reduce the activation energy required to initiate the reaction. Thus, if Line A represents the non-catalyzed reaction with a higher activation energy, while Line B shows the lowered activation energy due to enzyme action, it supports the conclusion which line corresponds to the enzyme-catalyzed reaction.