Enzymes enhance the rate of reaction by

Options

A. forming a reactant-product complex
B. changing the equilibrium point of the reaction
C. combining with the product as soon as it is formed
D. lowering the activation energy of the reaction

Explanation

### Step-by-Step Solution:

1. **Understanding Enzymes**: Enzymes are biological catalysts that speed up chemical reactions in living organisms. They are crucial for various biochemical processes.

2. **Activation Energy Concept**: Every chemical reaction requires a certain amount of energy to start, known as activation energy. This is the energy needed to break the bonds in the reactants so that they can be transformed into products.

3. **Role of Enzymes**: Enzymes enhance the rate of reaction by lowering the activation energy required for the reaction to occur. This means that with the presence of an enzyme, the reactants can more easily overcome the energy barrier to form products.

4. **Mechanism of Action**: When an enzyme is introduced to a reaction, it binds to the substrate (the reactants) to form an enzyme-substrate complex. This complex stabilizes the transition state and reduces the energy required for the reaction, allowing it to proceed more quickly.

5. **Example of Enzyme Activity**: For instance, the enzyme sucrase catalyzes the hydrolysis of sucrose into glucose and fructose. Without sucrase, the activation energy required is very high (32,000 calories per mole), but with sucrase, it is significantly reduced to 9,000 calories per mole.

6. **Conclusion**: Therefore, the correct answer to the question is that enzymes enhance the rate of reaction by lowering the activation energy required for the reaction to occur.

### Final Answer:
Enzymes enhance the rate of reaction by lowering the activation energy required for the reaction to occur.