Write the structure of alanine at pH = 2 and pH = 10.

Options

A. `NH_(2)-overset(CH_(3))overset(|)(CH)-COO^(-),H_(2)overset(+)N-overset(CH_(3))overset(|)(CH)-COOH`
B. `H_(2)overset+N-overset(CH_(3))overset(|)(CH)-COO^(-),H_(2)overset(+)N-overset(CH_(3))overset(|)(CH)-COOH`
C. `H_(3)overset+N-overset(CH_(3))overset(|)(CH)-COOH,NH_(2)-overset(CH_(3))overset(|)(CH)-COO^(-)`
D. `NH_(2)-overset(CH_(3))overset(|)(CH)-COO^(-),H_(2)overset(+)N-overset(CH_(3))overset(|)(CH)-COO`

Answer

To determine the structure of alanine at pH = 2 and pH = 10, we need to consider the behavior of alanine in acidic and basic conditions.

### Step 1: Understand the Structure of Alanine
Alanine (C3H7NO2) is an amino acid with the following structure:
- Amino group (NH2)
- A central carbon (C)
- A carboxylic acid group (COOH)
- A methyl group (CH3)

The structure can be represented as:
```
NH2
|
CH3-C-COOH
```

### Step 2: Analyze the Structure at pH = 2
At pH = 2, the environment is acidic. In this condition, the amino group (NH2) can accept a proton (H+), becoming positively charged (NH3+). The carboxylic acid group (COOH) remains protonated and does not lose its hydrogen.

The structure of alanine at pH = 2 is:
```
NH3+
|
CH3-C-COOH
```

### Step 3: Analyze the Structure at pH = 10
At pH = 10, the environment is basic. In this condition, the carboxylic acid group (COOH) can lose a proton (H+), becoming negatively charged (COO-). The amino group (NH2) remains unchanged as it does not accept a proton in this basic environment.

The structure of alanine at pH = 10 is:
```
NH2
|
CH3-C-COO-
```

### Summary of Structures:
- At **pH = 2**: Alanine exists as a cation (NH3+).
- At **pH = 10**: Alanine exists as an anion (COO-).

### Final Structures:
1. **At pH = 2**:
```
NH3+
|
CH3-C-COOH
```

2. **At pH = 10**:
```
NH2
|
CH3-C-COO-
```