An example of aromatic amino acid is

Options

A. tyrosine
B. phenylalanine
C. trytophan
D. all of these

Explanation

To answer the question "An example of aromatic amino acid is," we can follow these steps:

### Step-by-Step Solution:

1. **Define Aromatic Amino Acids**:
Aromatic amino acids are those that contain an aromatic ring in their structure. An aromatic ring is characterized by being cyclic, planar, and having an odd number of π (pi) electrons.

2. **Identify Features of Aromatic Rings**:
- **Cyclic Structure**: The ring must be closed with no openings.
- **Planarity**: The atoms in the ring must lie in the same plane.
- **Electron Configuration**: It must have an odd number of π electrons, typically following Huckel's rule.

3. **Examples of Aromatic Amino Acids**:
- **Tyrosine**: This amino acid contains a phenolic aromatic ring, making it an aromatic amino acid.
- **Phenylalanine**: This amino acid contains a benzene ring, which qualifies it as an aromatic amino acid.
- **Tryptophan**: This amino acid contains an indole ring, which is also aromatic.

4. **Conclusion**:
The examples of aromatic amino acids include tyrosine, phenylalanine, and tryptophan. Therefore, any of these can be cited as an example of an aromatic amino acid.

### Final Answer:
An example of an aromatic amino acid is **tyrosine**, **phenylalanine**, or **tryptophan**.

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