Biology 9700 · AS & A Level · Movement into and out of cells

Movement into and out of cells — practice question

The diagram illustrates ions being transported across the cell surface membrane. Within the cell, the concentration of sodium ions ($\text{Na}^+$) is low, while the concentration of potassium ions ($\text{K}^+$) is high. Outside the cell, $\text{K}^+$ is at a low concentration and $\text{Na}^+$ is at a high concentration. The carrier molecule is a pump that swaps $\text{Na}^+$ with $\text{K}^+$. Which ionic movements do the arrows show?

  • Aactive transport of $\text{K}^+$: 2; active transport of $\text{Na}^+$: 3; diffusion of $\text{Na}^+$: 1; diffusion of $\text{K}^+$: 4
  • Bactive transport of $\text{K}^+$: 2; active transport of $\text{Na}^+$: 3; diffusion of $\text{Na}^+$: 4; diffusion of $\text{K}^+$: 1
  • Cactive transport of $\text{K}^+$: 3; active transport of $\text{Na}^+$: 2; diffusion of $\text{Na}^+$: 1; diffusion of $\text{K}^+$: 4
  • Dactive transport of $\text{K}^+$: 3; active transport of $\text{Na}^+$: 2; diffusion of $\text{Na}^+$: 4; diffusion of $\text{K}^+$: 1

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