Choose the correct statement about isoelectric point

Options

A. If pH `gt` isoelectric point amino acid will move towards cathode
B. At this point amino acid is present in the form of Zwitter ion
C. If pH `lt` isoelectric point, amino acid will move towards anode
D. Al this point amino acids are basic in nature

Answer

To solve the question regarding the isoelectric point of amino acids, let's analyze the given options step by step.

### Step 1: Understand the Concept of Isoelectric Point
The isoelectric point (pI) is defined as the pH at which an amino acid exists predominantly in its zwitterion form. A zwitterion is a molecule that has both positive and negative charges but is overall neutral.

### Step 2: Analyze Each Option
Now, let's evaluate each of the options provided in the question:

**Option A:** "If pH greater than isoelectric point, amino acid will move towards cathode."
- **Analysis:** When the pH is greater than the isoelectric point, the amino acid exists in anionic form (negatively charged) and will move towards the anode (positively charged electrode), not the cathode. Therefore, this statement is incorrect.

**Option B:** "At this point amino acid is present in form of zwitterion."
- **Analysis:** This statement is correct. At the isoelectric point, the amino acid exists in its zwitterion form, where it has both a positive and a negative charge, making it neutral overall.

**Option C:** "If pH is less than isoelectric point, amino acid will move towards anode."
- **Analysis:** When the pH is less than the isoelectric point, the amino acid exists in cationic form (positively charged) and will move towards the cathode (negatively charged electrode). Therefore, this statement is incorrect.

**Option D:** "At this point amino acids are basic in nature."
- **Analysis:** At the isoelectric point, amino acids are neutral due to the zwitterion form. They can act as either acids or bases depending on the pH, but they are not strictly basic at this point. Thus, this statement is also incorrect.

### Conclusion
After analyzing all the options, the correct statement about the isoelectric point is:
**Option B:** "At this point amino acid is present in form of zwitterion."