Question

Iodine is necessary for the synthesis of which hormone?

• A. Adrenaline
• B. Thyroxin
• C. Auxin
• D. Insulin

Answer 1

The correct option is B

Thyroxin

The correct option is B.

Explanation of correct option:

1. Iodine is required for thyroid hormone synthesis and can be obtained from food.
2. Iodine is absorbed in the stomach and small intestine, and the sodium/ iodide symporter concentrates it from the bloodstream into the thyroid follicular cell.
3. T4(tetra-iodothyronine) is the most important thyroid hormone produced by the thyroid gland.
4. T4 in the bloodstream is taken up by cells and de-iodinated in the cytoplasm to form tri-iodothyronine (T3).
5. Thyroid hormones have two types of physiological effects:
   1. Growth and development
   2. Control of the body's metabolic processes.

Explanation of incorrect option:

Option A:

1. One of the endocrine glands, the adrenal gland, which is situated on the kidneys as a cap-like structure, secretes the adrenaline hormone.
2. It is important in the fight-or-flight response because it quickly boosts cardiac output by causing forceful contractions and rising blood pressure, which increases heart rate and blood supply to numerous organs.

Option C:

1. The term 'auxin' refers to indole-3-acetic acid (IAA) as well as other natural and synthetic chemicals with growth-regulating capabilities.
2. Auxins are created primarily by the developing apices of stems and roots, from which they travel to their action areas.

Option D:

1. Insulin is a hormone that allows glucose from the blood to enter cells, providing them with the energy they need to function.
2. Insulin deficiency is a major factor in the development of diabetes.

Final answer: Iodine is necessary for the synthesis of thyroxine.