Facilitated diffusion

The

{Na}^{+}

K^{+}

ATPase, or sodium-potassium pump, is a membrane protein that uses energy from ATP hydrolysis to transport sodium ions (

{Na}^{+}

) and potassium ions (

K^{+}

) against their concentration gradients. The steps of ion exchange carried out by the

{Na}^{+}

K^{+}

ATPase are depicted in the following diagram.

Given the concentration gradient established by the Na $^{+}$ ‍/K $^{+}$ ‍ ATPase, which of the following movements can occur?

(Choice A)
${Na}^{+}$ ‍ can move into the cell by passive transport.
(Choice B)
${Na}^{+}$ ‍ can move out of the cell without using energy from ATP hydrolysis.
(Choice C)
$K^{+}$ ‍ can move out of the cell by directly diffusing through the cell membrane.
(Choice D)
$K^{+}$ ‍ can move into the cell by passive transport.

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