Among the statement given below, which statements /s is / are correct regarding the relationship between enzyme and substrate ?
I. Above a certain concentration of substrate , an enzyme reaches its maximum rate of reaction
II. Increasing the substrate concentration to a higher level doesn't reverse the effects of a competitive inhibitor.
III At high substrate concentration , a non competitive inhibitor no longer affects the enzyme activity .
IV. The higher the concentration of substrate the faster an enzyme can cataylse a reaction.

Options

A. I and II only
B. I,II and IV
C. I only
D. III and IV only

Answer

To solve the question regarding the relationship between enzymes and substrates, we will analyze each statement one by one.

### Step-by-Step Solution:

1. **Statement I: Above a certain concentration of substrate, an enzyme reaches its maximum rate of reaction.**
- This statement is **correct**. As substrate concentration increases, the enzyme becomes saturated with substrate molecules. Once all active sites of the enzyme are occupied, the rate of reaction reaches its maximum (Vmax). Therefore, this statement is true.

2. **Statement II: Increasing the substrate concentration to a higher level doesn't reverse the effects of a competitive inhibitor.**
- This statement is **incorrect**. Competitive inhibitors compete with the substrate for the active site of the enzyme. Increasing the substrate concentration can outcompete the inhibitor, thus reversing its effects. Hence, this statement is false.

3. **Statement III: At high substrate concentration, a non-competitive inhibitor no longer affects the enzyme activity.**
- This statement is **incorrect**. Non-competitive inhibitors bind to an enzyme regardless of whether the substrate is bound or not. Therefore, even at high substrate concentrations, non-competitive inhibitors will still affect enzyme activity. Thus, this statement is false.

4. **Statement IV: The higher the concentration of substrate, the faster an enzyme can catalyze a reaction.**
- This statement is **partially correct**. Initially, as substrate concentration increases, the rate of reaction increases. However, once the enzyme is saturated, further increases in substrate concentration do not increase the reaction rate. Therefore, this statement is misleading and can be considered false in the context of enzyme saturation.

### Conclusion:
- The only correct statement is **Statement I**.
- Therefore, the correct answer is that only **Statement I** is true.