`alpha`- Amino acids are the building blocks of proteins. About 20 `alpha`-amino acids have been isolated by the hydrolysis of proteins. All these amino acids except glycine are chiral and have L-configuration. Ten amino acids (valine , leucine, isoleucine , phenylalanine, methionine , trytophan , threonine , lysine , arginine and histidine) which the body cannot synthesize are called essential amino acids. The remaining ten are called non -essential amino acids. All `alpha`-amino acids exist are zwitterions each of which has a specific isoelectric point. Above isoelectric point , a `alpha`-amino acid exists as an anion. Two, three or many `alpha`-amino acids join together to form di-,tri -or polypeptides or proteins respectively. Each polypeptides or protein has a free amino group at one end called the N-terminal end and a free carboxyl group at the other end called the C-terimal end. Sanger's reagent (i.e., 2,4-dinitrofluorobenzene) is used to determine the N-terminal end while C-terimal end is determined by hydrazinolysis.
The acid showing salt-like character in aqueous solution is

Options

A. acetic acid
B. benzoic acid
C. formic acid
D. `alpha`-aminoacetic acid.

Answer

To solve the question regarding which acid shows salt-like character in aqueous solution, we need to analyze the properties of amino acids and their behavior in solution.

### Step-by-Step Solution:

1. **Understanding Amino Acids**:
- Alpha amino acids are organic compounds that contain both an amino group (-NH2) and a carboxyl group (-COOH). This dual functionality allows them to act as acids and bases.

2. **Zwitterionic Form**:
- In an aqueous solution, amino acids exist predominantly in a zwitterionic form. This means they have both a positive charge (from the amino group) and a negative charge (from the carboxyl group) but are overall neutral.

3. **Salt-like Character**:
- The zwitterionic nature of amino acids gives them a salt-like character in solution. This is because they can dissociate into ions, similar to how salts behave in water.

4. **Identifying the Correct Acid**:
- The question asks for an acid that shows salt-like character. Among the options provided, we need to identify which one is an amino acid.
- The options given include acetic acid, benzoic acid, formic acid, and alpha amino acetic acid.

5. **Evaluating the Options**:
- Acetic acid (CH3COOH) is not an amino acid.
- Benzoic acid (C6H5COOH) is also not an amino acid.
- Formic acid (HCOOH) is not an amino acid.
- Alpha amino acetic acid (glycine, NH2CH2COOH) is indeed an amino acid.

6. **Conclusion**:
- Since glycine is an amino acid and can exist in a zwitterionic form in solution, it shows salt-like character. Therefore, the correct answer is alpha amino acetic acid.

### Final Answer:
The acid showing salt-like character in aqueous solution is **alpha amino acetic acid (glycine)**.

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