To solve the problem regarding the isoelectric point of a gelatin solution, we will follow these steps:
### Step-by-Step Solution:
1. **Understanding the Isoelectric Point (pI)**:
- The isoelectric point is the pH at which a molecule carries no net electrical charge. For gelatin, the given isoelectric point is 4.7.
2. **Analyzing pH Conditions**:
- We need to consider two scenarios based on the pH relative to the isoelectric point:
- Case 1: pH > 4.7
- Case 2: pH < 4.7
3. **Case 1: pH > 4.7**:
- At pH greater than 4.7, the gelatin molecules will be in their anionic form (negatively charged).
- Since they are negatively charged, they will move towards the positively charged electrode, which is the anode.
4. **Case 2: pH < 4.7**:
- At pH less than 4.7, the gelatin molecules will be in their cationic form (positively charged).
- Since they are positively charged, they will move towards the negatively charged electrode, which is the cathode.
5. **Evaluating the Options**:
- Based on the analysis:
- If pH < 4.7, the gelatin is positively charged and moves towards the cathode.
- If pH > 4.7, the gelatin is negatively charged and moves towards the anode.
- We will evaluate the provided options based on these conditions.
6. **Identifying the Correct Option**:
- Option A: pH < 4.7, negatively charged, moves towards cathode (Incorrect)
- Option B: pH < 4.7, positively charged, moves towards anode (Incorrect)
- Option C: pH > 4.7, positively charged, moves towards anode (Incorrect)
- Option D: pH > 4.7, negatively charged, moves towards anode (Correct)
### Conclusion:
The correct answer is **Option D**: If pH > 4.7, it is negatively charged and moves towards the anode.
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