Which amino acid pair has the simplest and most complex structures?

Options

A. Tryptophan and Methionine
B. Cysteine and Glycine
C. Glycine and Methionine
D. Glycine and Tryptophan

Answer

To determine which amino acid pair has the simplest and most complex structures, we can analyze the structures of the given amino acids.

### Step-by-Step Solution:

1. **Understanding Amino Acids**:
- Amino acids are organic compounds that contain an amino group (-NH2), a carboxyl group (-COOH), and a variable side chain (R group) that determines the characteristics of each amino acid.

2. **Identifying the Simplest Amino Acid**:
- The simplest amino acid is **glycine**.
- Glycine has the chemical formula **C2H5NO2**.
- Its structure is characterized by having a hydrogen atom as its side chain (R group), making it the simplest in terms of molecular complexity.

3. **Identifying the Most Complex Amino Acid**:
- The most complex amino acid is **tryptophan**.
- Tryptophan has the chemical formula **C11H12N2O2** and features an indole group in its side chain, which includes a fused benzene ring and a pyrrole ring.
- This complex structure contributes to its higher molecular complexity compared to other amino acids.

4. **Comparing Other Options**:
- **Cysteine** and **methionine** both contain sulfur in their side chains, but their structures are not as complex as tryptophan.
- **Glycine** is consistently the simplest due to its minimal side chain.

5. **Conclusion**:
- The pair of amino acids that represents the simplest and most complex structures is **glycine (simplest)** and **tryptophan (most complex)**.

### Final Answer:
- The amino acid pair with the simplest and most complex structures is **glycine and tryptophan**.