The amino acid with lowest molecular weight is:

Options

A. Serine
B. Glycine
C. Cysteine
D. Threonine

Answer

To determine the amino acid with the lowest molecular weight, we will follow these steps:

### Step 1: Understand the Structure of Amino Acids
Amino acids are organic compounds that contain an amine group (-NH2), a carboxylic acid group (-COOH), and a unique side chain or R group that varies among different amino acids.

### Step 2: Identify the Given Options
The question provides four amino acids to compare:
1. Serine
2. Glycine
3. Cysteine
4. Threonine

### Step 3: Research Molecular Weights
Next, we need to find the molecular weights of the listed amino acids:
- **Serine**: 105.09 g/mol
- **Glycine**: 75.07 g/mol
- **Cysteine**: 121.2 g/mol
- **Threonine**: 119.1 g/mol

### Step 4: Compare the Molecular Weights
Now, we compare the molecular weights:
- Serine: 105.09 g/mol
- Glycine: 75.07 g/mol
- Cysteine: 121.2 g/mol
- Threonine: 119.1 g/mol

### Step 5: Identify the Lowest Molecular Weight
From the comparison, we can see that glycine has the lowest molecular weight at 75.07 g/mol.

### Conclusion
Thus, the amino acid with the lowest molecular weight is **Glycine**.

---