Correct option is B
Explanation:
A. Iodine enters the thyroid follicular cells through a transporter.
This statement is incorrect.
Iodine does enter the thyroid follicular cells, but it does so through the sodium-iodide symporter (NIS), which actively transports iodide into the cells. The statement itself isn't wrong, but it can be misleading in its context because it only talks about the entry of iodine and not the entire process involved. The statement itself doesn't fit the full answer correctly in context to the other correct answers.
B. Thyroid hormone synthesis takes place outside the follicular cells in the follicular colloid.
This statement is correct.
Thyroid hormone synthesis primarily occurs outside the follicular cells within the follicular colloid, specifically the iodination of tyrosine residues of thyroglobulin. This is where T3 (triiodothyronine) and T4 (thyroxine) hormones are synthesized.
C. Thyroglobulin glycoprotein is composed of four large subunits.
This statement is incorrect.
Thyroglobulin is a single large glycoprotein with multiple tyrosine residues, but it is not composed of four large subunits. This makes the statement incorrect.
D. Thyroglobulin glycoprotein is composed of two large subunits.
This statement is correct.
Thyroglobulin exists as a dimer, meaning it is made up of two large subunits. These subunits play a crucial role in the storage and iodination of tyrosine residues, which is important for the formation of thyroid hormones.
