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

Movement into and out of cells — practice question

The diagram illustrates ion movement across the cell surface membrane. Within the cell, the concentration of sodium ions ($\text{Na}^+$) is low and the concentration of potassium ions ($\text{K}^+$) is high. Outside the cell, there is a low concentration of $\text{K}^+$ and a high concentration of $\text{Na}^+$. The carrier molecule acts as a pump that swaps $\text{Na}^+$ for $\text{K}^+$. 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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