The function of an enzyme is to

Options

A. cause chemical reaction
B. change the rate of chemical reaction
C. change the equailibrum
D. change the directions of reactions

Answer

To answer the question "The function of an enzyme is to," we need to analyze the options provided and understand the role of enzymes in biochemical reactions.

### Step-by-Step Solution:

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

2. **Evaluating the Options**:
- **Option A: Cause chemical reaction**: Enzymes do not cause reactions to occur; they facilitate reactions that would happen anyway but at a much slower rate.
- **Option B: Change the rate of chemical reaction**: This is a correct statement. Enzymes increase the rate of chemical reactions by lowering the activation energy required for the reaction to proceed.
- **Option C: Change the equilibrium**: Enzymes do not change the equilibrium of a reaction; they only help reach equilibrium faster.
- **Option D: Change the direction of the reaction**: Enzymes do not change the direction of a reaction; they only speed up the reaction in the direction it is already going.

3. **Conclusion**: Based on the analysis of the options, the function of an enzyme is best described by **Option B**, which states that enzymes change the rate of chemical reactions.

### Final Answer:
The correct answer is **Option B: Change the rate of chemical reaction**.

---