Question

In secondary active transport, the sodium iodide transporter moves iodide into the thyroid gland from the blood plasma.  It cotransports one I^- for every two Na⁺ ions.  In mammals, this protein is found predominantly in the thyroid gland, but also in salivary glands, kidneys, gastric mucose, ovaries, and, importantly, in mammary glands, where it is responsible for uptake of iodide into milk, delivering this important element needed to make thyroid hormones.    The point of this process is the ACTIVE transport of iodide.

1. Where does the cell get the energy to do the active transport of iodide in this case? (what “fuels” this transporter – answer with the most direct form of energy)?  ONE PHRASE ANSWER
2. Is this a symporter or antiporter? ONE WORD ANSWER
3. Diagram this process (so sketch a membrane and the necessary proteins, showing the directional flow of all mentioned solutes and their concentration gradients.  (See figure 5.19 from your textbook for an example, but yours doesn’t have to be so elaborate!  You should also review figure 5.20.)

Answer 1

a. Active transport mediated by  Na⁺/K⁺-ATPase.

b. Symporter- sodium-iodide symporter actively cotransport two sodium cations per each iodide anion.

c.

.