The main difference between an enzyme catalyzed and uncatalyzed reaction is that the former has

Options

A. lower energy of activation
B. lower free energy
C. ability to use all available substrate
D. little influence of external conditions

Answer

### Step-by-Step Solution:

1. **Understanding Enzyme-Catalyzed Reactions**:
- Enzymes are biological catalysts that speed up chemical reactions by lowering the activation energy required for the reaction to occur.
- In an enzyme-catalyzed reaction, the enzyme binds to the substrate to form an enzyme-substrate complex, which then converts to the product.

2. **Comparing with Uncatalyzed Reactions**:
- In an uncatalyzed reaction, the substrate molecules react without the assistance of an enzyme.
- This process is generally slower because it requires a higher activation energy to initiate the reaction.

3. **Activation Energy**:
- Activation energy is the minimum energy required for a reaction to occur.
- In enzyme-catalyzed reactions, the activation energy is significantly lower compared to uncatalyzed reactions.

4. **Graphical Representation**:
- If we plot a graph with the energy of the reactants on the Y-axis and the progress of the reaction on the X-axis, we can visualize the difference.
- The graph for an uncatalyzed reaction shows a higher peak (higher activation energy) compared to the graph for an enzyme-catalyzed reaction, which shows a lower peak (lower activation energy).

5. **Conclusion**:
- The main difference between enzyme-catalyzed and uncatalyzed reactions is that the enzyme-catalyzed reaction has a lower activation energy requirement, which allows the reaction to proceed more rapidly.

### Final Answer:
The main difference between an enzyme-catalyzed and uncatalyzed reaction is that the former has a lower activation energy requirement.