Final answer:
The correct answer is Reaction 1 (A). Enzymes decrease the activation energy required for a given chemical reaction to occur.
Step-by-step explanation:
The correct answer is Reaction 1 (A). Enzymes are biological catalysts that increase the rate of chemical reactions by lowering the activation energy required for the reaction to occur. In Figure 2.13, it is shown that with the help of an enzyme, less energy is needed for a reaction to begin compared to a reaction without an enzyme present. This means that Reaction 1, with an enzyme present, would represent the same reaction as Reaction 2 without an enzyme present.
To identify the reaction with an enzyme present compared to Reaction 2 without an enzyme, we look for the one with a lower activation energy peak on the reaction diagram. This is indicative of the role of enzymes as biological catalysts that speed up reactions by reducing the activation energy required.
If Reaction 2 is described as a reaction without an enzyme present, and we need to identify which reaction represents the same reaction with an enzyme present, we should look for a reaction that has a lower activation energy than Reaction 2. This is because enzymes function as biological catalysts that lower the activation energy needed for a reaction, thereby increasing the rate at which the reaction occurs. It's important to note that the presence of an enzyme does not affect the overall free energy change of the reaction, only the energy required to get the reaction started.
Based on the information provided, which suggests that enzymes decrease the activation energy, we would expect the reaction with an enzyme present to show a lower peak on the reaction diagram compared to the reaction without the enzyme. Therefore, the corresponding option (A, B, C, or D) that shows a reaction profile with a lower activation energy peak compared to Reaction 2 represents the reaction with the enzyme present.