Which of the following statements is NOT true with respect to potassium ion chan

Question

Which of the following statements is NOT true with respect to potassium ion channels?

A. The hinge region of the proteins that move as a result of external influences has Gly residues, which facilitates protein movement, given its small size. B. External influences, such as a change in pH or the binding of an appropriate ligand, alter the conformation of the channel protein, opening or closing it as appropriate. C. The channels have closed and open conformations. D. The binding of the first potassium ion induces a conformational change in the channel protein that allows it to selectively bind only additional potassium ions.

Explanation / Answer

D. False.

For the conductance, the filter of the K+ channel requires the presence of two K+ ions (not one ion). Only after the entry of the second K+ ion did the confmational change occur, and allows additional potassium ions to move through. Some fraction of the ion binding energy is used to change the filter's structure. The binding of second ion is required to provide sufficient energy to induce a change in the structure of the channel protein.

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