Labeling an Energy Diagram: Enzyme-Catalyzed vs. Uncatalyzed Reactions

Q: Use the word bank to label the diagram below (energy diagram showing enzyme-catalyzed and uncatalyzed reactions).

Background

Topic: Enzyme Function and Activation Energy

This question tests your understanding of how enzymes affect the energy profile of a chemical reaction, specifically by lowering the activation energy required for the reaction to proceed. The diagram compares the energy changes in a reaction with and without an enzyme.

Key Terms and Concepts

• Activation Energy (EA): The energy barrier that must be overcome for reactants to be converted into products.

• ΔG (Change in Free Energy): The difference in energy between reactants and products; determines if a reaction is spontaneous.

• Reactants and Products: The starting and ending substances in a chemical reaction.

• Course of Reaction: The pathway from reactants to products, shown as a curve on the diagram.

• Enzyme-Catalyzed vs. Uncatalyzed: Enzymes lower the activation energy, making the reaction proceed faster.

Step-by-Step Guidance

1. Examine the two curves on the diagram. The higher curve (black) represents the reaction without an enzyme, while the lower curve (red) represents the reaction with an enzyme.

2. Identify the activation energy (EA) for each curve. The vertical arrows indicate the energy barrier for each pathway. The taller arrow corresponds to the uncatalyzed reaction, and the shorter arrow to the catalyzed reaction.

3. Locate the reactants and products on the y-axis. The starting point of each curve is the energy level of the reactants, and the endpoint is the energy level of the products.

4. The difference in height between reactants and products (yellow arrow) represents ΔG, the overall change in free energy for the reaction.

5. Use the word bank to match each label to the correct part of the diagram: "Course of reaction with enzyme," "Course of reaction without enzyme," "EA with enzyme," "EA without enzyme," "ΔG," "Reactants," and "Products."

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