Question

because ions carry a charge (positive or negative), their transport across a membrane is governed not only by concentration gradients across the membrane but also by differences in charge (electrical gradient) across the plasma membrane make up the electrochemical gradient. consider the plasma membrane of an animal cell that contains a sodium - potassium pump on the concentrations of na⁺ and k⁺ as well as the distribution of charge across the plasma membrane is indicated in the figure below. outside cell sodium - potassium pump na⁺ channel k⁺ channel na⁺ high k⁺ low 3 na⁺ 2 k⁺ na⁺ low k⁺ high inside cell which of the following statements correctly describe(s) the driving forces for diffusion of na⁺ and k⁺ ions through their respective channels? select all that apply. view available hint(s) the diffusion of na⁺ ions into the cell is facilitated by the na⁺ concentration gradient across the plasma membrane. the diffusion of na⁺ ions into the cell is impeded by the electrical gradient across the plasma membrane. the diffusion of k⁺ ions out of the cell is impeded by the k⁺ concentration gradient across the plasma membrane. the diffusion of k⁺ ions out of the cell is impeded by the electrical gradient across the plasma membrane. the electrochemical gradient is larger for na⁺ than for k⁺

Explanation:

1. For sodium ($Na^+$) ions: The concentration of $Na^+$ is higher outside the cell and lower inside. So, the concentration - gradient favors the diffusion of $Na^+$ into the cell. Also, the inside of the cell is negatively charged relative to the outside, which is a driving - force for the positively charged $Na^+$ ions to enter the cell. So, the electrical gradient also favors $Na^+$ entry.
2. For potassium ($K^+$) ions: The concentration of $K^+$ is higher inside the cell and lower outside. So, the concentration - gradient favors the diffusion of $K^+$ out of the cell. However, the inside of the cell is negatively charged, which opposes the outward movement of positively charged $K^+$ ions. So, the electrical gradient impedes the diffusion of $K^+$ out of the cell.
3. The electrochemical gradient takes into account both the concentration and electrical gradients. Since the concentration and electrical differences for $Na^+$ are more significant compared to $K^+$, the electrochemical gradient is larger for $Na^+$ than for $K^+$.

Answer:

The diffusion of $Na^+$ ions into the cell is facilitated by the $Na^+$ concentration gradient across the plasma membrane.
The diffusion of $K^+$ ions out of the cell is impeded by the electrical gradient across the plasma membrane.
The electrochemical gradient is larger for $Na^+$ than for $K^+$.