Which of the following best describes the conditions established across a cell membrane by the action of the Na\textsuperscript{+}/K\textsuperscript{+} pump?

• A. Higher concentration of K\textsuperscript{+} outside the cell and higher concentration of Na\textsuperscript{+} inside the cell
• B. Higher concentration of Na\textsuperscript{+} outside the cell and higher concentration of K\textsuperscript{+} inside the cell, creating an electrochemical gradient
• C. No net movement of ions across the membrane
• D. Equal concentrations of Na\textsuperscript{+} and K\textsuperscript{+} on both sides of the membrane

Answer: (B)

Verified step by step guidance

1. Understand the role of the Na⁺/K⁺ pump: The sodium-potassium pump is an active transport mechanism that uses ATP to move ions against their concentration gradients. Specifically, it pumps Na⁺ ions out of the cell and K⁺ ions into the cell.
2. Recognize the concentration gradients created: The pump establishes a higher concentration of Na⁺ outside the cell and a higher concentration of K⁺ inside the cell. This creates an electrochemical gradient across the membrane.
3. Consider the energy requirements: The pump requires energy in the form of ATP because it moves ions against their natural diffusion gradients, which is an energetically unfavorable process.
4. Understand the significance of the electrochemical gradient: The gradient is essential for various cellular processes, including nerve impulse transmission and muscle contraction. It also contributes to the resting membrane potential of the cell.
5. Eliminate incorrect options: Based on the function of the Na⁺/K⁺ pump, discard options that suggest equal concentrations of ions, no net movement, or reversed gradients. The correct description is a higher concentration of Na⁺ outside the cell and K⁺ inside the cell, creating an electrochemical gradient.