Question

Thyroxine produced in the thyroid gland is an iodinated derivative of _______.

• A. Threonine
• B. Lysine
• C. Tyrosine
• D. Tryptophan

Answer 1

The Correct Option is C

Thyroxine is a hormone produced by the thyroid gland and is an iodinated derivative of tyrosine, which is an amino acid. The thyroid gland adds iodine to tyrosine to form thyroxine (T4) and triiodothyronine (T3), both of which play essential roles in regulating metabolism.

Explanation: 

• Option A: Tyrosine - Correct. Thyroxine is an iodinated derivative of tyrosine, which is the precursor for thyroid hormones.
• Option B: Tryptophan - This is incorrect. Tryptophan is an amino acid, but it is not involved in the production of thyroxine.
• Option C: Threonine - This is incorrect. Threonine is an amino acid, but it is not related to the production of thyroxine.
• Option D: Lysine - This is incorrect. Lysine is an amino acid, but it does not play a role in the production of thyroxine.

Conclusion:

The correct answer is Option A: Tyrosine, as thyroxine is an iodinated derivative of tyrosine.

Answer 2

Thyroxine (T4) is a hormone produced in the thyroid gland. It is synthesized from the amino acid tyrosine. The synthesis involves the iodination of tyrosine molecules. The iodinated tyrosine forms diiodotyrosine (DIT) and monoiodotyrosine (MIT), which combine to form thyroxine (T4).

- Threonine is an amino acid, but it is not involved in the synthesis of thyroxine.
- Lysine is another amino acid that does not play a role in thyroxine synthesis.
- Tyrosine is the correct amino acid. It is the precursor for thyroxine after it undergoes iodination in the thyroid gland.
- Tryptophan is involved in serotonin production, but not in the synthesis of thyroxine.

Thus, thyroxine is an iodinated derivative of tyrosine.