Which of the following shows competitive inhibition ?

Options

A. Hexokinase
B. Succinate dehyrogenase
C. Phosphofructokinase
D. All the above

Answer

To determine which of the following shows competitive inhibition, we need to understand the concept of competitive inhibition in enzymatic reactions.

### Step-by-Step Solution:

1. **Define Competitive Inhibition**:
- Competitive inhibition occurs when an inhibitor competes with the substrate for binding to the active site of an enzyme. Both the substrate and the inhibitor have structural similarities that allow them to bind to the same active site.

2. **Identify the Enzymes and Their Inhibitors**:
- We need to analyze the options provided in the question to see if they have known competitive inhibitors.

3. **Examine Each Option**:
- **Option 1: Hexokinase**:
- The competitive inhibitor for hexokinase is glucose 6-phosphate (G6P). Therefore, this option shows competitive inhibition.

- **Option 2: Succinate Dehydrogenase**:
- Succinate dehydrogenase has competitive inhibitors such as malonate. Thus, this option also shows competitive inhibition.

- **Option 3: Phosphofructokinase**:
- Phosphofructokinase has malonate as a competitive inhibitor as well. Hence, this option shows competitive inhibition too.

4. **Conclusion**:
- Since all the options provided (hexokinase, succinate dehydrogenase, and phosphofructokinase) have competitive inhibitors, the correct answer is **Option 4: All of the above**.

### Final Answer:
- The correct answer is **Option 4: All of the above**.