One of the following amino acids does not contain sulfur
(a) Tryptophan
(b) Methionine
(c) Cysteine
(d) Homocysteine

Options

A. Tryptophan
B. Methionine
C. Cystine
D. HomoCysteine

Answer

To determine which amino acid does not contain sulfur, we can analyze each of the given options:

1. **Tryptophan (Option a)**: Tryptophan is an aromatic amino acid. Its structure does not include sulfur. Therefore, it does not contain sulfur.

2. **Methionine (Option b)**: Methionine is known to be a sulfur-containing amino acid. It has a thioether group in its structure, which includes sulfur.

3. **Cysteine (Option c)**: Cysteine is another sulfur-containing amino acid. It has a thiol group (-SH) in its structure, which means it contains sulfur.

4. **Homocysteine (Option d)**: Homocysteine is derived from methionine and also contains sulfur in its structure.

After analyzing all the options, we can conclude that:

- Tryptophan does not contain sulfur.
- Methionine, cysteine, and homocysteine all contain sulfur.

Thus, the amino acid that does not contain sulfur is **Tryptophan (Option a)**.

### Step-by-Step Solution:
1. **Identify the amino acids listed in the options**: Tryptophan, Methionine, Cysteine, and Homocysteine.
2. **Check each amino acid for sulfur content**:
- Tryptophan: No sulfur.
- Methionine: Contains sulfur.
- Cysteine: Contains sulfur.
- Homocysteine: Contains sulfur.
3. **Determine which amino acid does not contain sulfur**: Tryptophan is the only amino acid that does not contain sulfur.
4. **Conclude the answer**: The correct answer is Tryptophan (Option a).