Question

What process allows Na+ and K+ to move in and out of the cell simultaneously?

Answer 1

Answer:

The correct answer is: C. Active Transport.

Explanation:

Because Na+ and K+ are ions, which makes them charged molecules, they can only diffuse through the cell membrane when using specialized protein channels. This is called facilitated diffusion and is a form of passive transport because sodium and potassium move following their gradients, which are made of the difference in concentration between the inside of the cell and the outside of the cell. For example, potassium is highly concentrated inside the cell and poorly concentrated outside the cell, so potassium diffuses from the inside to the outside to even the concentrations.

But the question asks in which process Na+ and K+ move in and out of the cell SIMULTANEOUSLY, so the answer is actually active transport. Active transport is the opposite of passive transport. While passive transport occurs naturally and doesn't need ATP (energy) to happen, active transport needs ATP because it moves molecules AGAINST their gradient. One of the most famous and important structures involved in active transport is the Na+/K+ pump, which consists of a specialized protein using energy to enter 2 potassium ions and take out 3 sodium ions at the same time. This Na+/K+ is fundamental to maintain the gradients, which are important for the correct functioning of many cells.