What is the Zwitterion?

Options

A. The carboxyl group can lose a proton and amino group can accept a proton in the aqueous solution with give rise to a dipolar ion
B. The carboxyl group can accept a proton and amino group can lose a proton in aqueous solution which give rise to a dipolar ion
C. The amino group can accept a proton and ester group can lose a proton in aqueous solution which give rise to dipolar ion
D. Thy amino group can lose a proton in aqueous solution and ester group can accept a proton in aqueous solution which give rise to the dipolar ion

Answer

### Step-by-Step Solution

1. **Definition of Zwitterion**: A zwitterion is a molecule that has both positive and negative charges but is overall electrically neutral. This typically occurs in amino acids, which contain both an amino group (-NH2) and a carboxyl group (-COOH).

2. **Formation of Zwitterion**: In an aqueous solution, the carboxyl group can lose a proton (H⁺), resulting in a negatively charged carboxylate ion (-COO⁻). Simultaneously, the amino group can accept a proton, resulting in a positively charged ammonium ion (-NH3⁺).

3. **Charge Distribution**: The presence of both these charged groups in the same molecule leads to a dipolar ion, which is characteristic of zwitterions. The molecule has a positive charge on one part (the ammonium ion) and a negative charge on another part (the carboxylate ion), but the overall charge of the molecule is neutral.

4. **Example in Amino Acids**: Most amino acids exist as zwitterions at physiological pH (around 7.4). For example, in the case of glycine (the simplest amino acid), it can be represented as:
- At low pH: NH3⁺ - CH2 - COOH (protonated amino group, protonated carboxyl)
- At neutral pH: NH3⁺ - CH2 - COO⁻ (protonated amino group, deprotonated carboxyl)
- At high pH: NH2 - CH2 - COO⁻ (deprotonated amino group, deprotonated carboxyl)

5. **Conclusion**: Thus, a zwitterion is specifically formed when the carboxyl group of an amino acid loses a proton and the amino group accepts a proton, resulting in a molecule that has both a positive and a negative charge.