Hormones thyroxin, adrenaline and the pigment melanin are formed from

Options

A. Tyrosine
B. Proline
C. Tryptophan
D. Glycine

Answer

To answer the question about the formation of the hormones thyroxine, adrenaline, and the pigment melanin, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Hormones and Pigment**: The question mentions three substances: thyroxine, adrenaline, and melanin.

2. **Understand Their Chemical Composition**:
- **Thyroxine** (T4) and **Triiodothyronine** (T3) are thyroid hormones that contain iodine.
- **Adrenaline** (also known as epinephrine) is a hormone produced by the adrenal glands.
- **Melanin** is a pigment responsible for coloration in skin, hair, and eyes.

3. **Determine the Precursor**:
- All three substances are derived from the amino acid **tyrosine**.
- Tyrosine is a non-essential amino acid that is important in the synthesis of several hormones and pigments.

4. **Explain the Synthesis**:
- **Thyroxine** is synthesized from tyrosine through the addition of iodine. Specifically, T4 is formed by the combination of tyrosine and four iodine atoms.
- **Adrenaline** is also derived from tyrosine through a series of enzymatic reactions that convert tyrosine into dopamine, then norepinephrine, and finally into adrenaline.
- **Melanin** is produced from tyrosine through a different pathway involving the enzyme tyrosinase, which catalyzes the conversion of tyrosine into dopa and then into melanin.

5. **Conclusion**: Therefore, the correct answer to the question is that thyroxine, adrenaline, and melanin are all formed from the amino acid **tyrosine**.

### Final Answer:
Thyroxine, adrenaline, and melanin are formed from the amino acid **tyrosine**.