Enzyme hexokinase is inhibited by excess glucose 6-P. It is

Answer

To solve the question regarding the inhibition of the enzyme hexokinase by excess glucose 6-phosphate, we can follow these steps:

### Step 1: Understand the Role of Hexokinase
Hexokinase is an enzyme that catalyzes the conversion of glucose to glucose 6-phosphate during glycolysis. This is an important step in glucose metabolism.

**Hint:** Remember that hexokinase is crucial for the first step of glycolysis.

### Step 2: Identify the Inhibition Mechanism
The question states that hexokinase is inhibited by excess glucose 6-phosphate. This suggests that when glucose 6-phosphate levels are high, they interfere with the activity of hexokinase.

**Hint:** Think about how the accumulation of a product can affect enzyme activity.

### Step 3: Define Feedback Inhibition
Feedback inhibition is a regulatory mechanism where the end product of a metabolic pathway inhibits an upstream process. In this case, glucose 6-phosphate (the product of the reaction catalyzed by hexokinase) inhibits the activity of hexokinase itself.

**Hint:** Consider how the body regulates metabolic pathways to maintain balance.

### Step 4: Analyze the Options
The options provided are:
- Competitive inhibition
- Feedback inhibition
- Allosteric inhibition
- Positive feedback

Since glucose 6-phosphate is an end product that inhibits the enzyme that produces it, this is a classic example of feedback inhibition.

**Hint:** Look for the option that describes a product inhibiting its own synthesis.

### Step 5: Conclusion
Based on the understanding of the mechanism and the definitions, the correct answer to the question is **feedback inhibition**.

**Final Answer:** Feedback inhibition.