At resting membrane potential in a neuron, which is true of the forces responsible for the movement of potassium (directed into or out of the cell)?
Select one:
a. Chemical and electrical gradients are directed outward
b. The chemical gradient is outward while the electrical gradient is inward
c. Chemical and electrical gradients are directed inward
d. Chemical gradient is inward while the electrical gradient is outward Clear my choice
The correct answer and explanation is:
The correct answer is b. The chemical gradient is outward while the electrical gradient is inward.
At the resting membrane potential in a neuron, potassium (K⁺) ions are influenced by both chemical and electrical gradients, which play a significant role in determining the movement of ions across the cell membrane.
- Chemical Gradient: This gradient is caused by differences in the concentration of potassium ions across the membrane. The concentration of potassium is much higher inside the cell compared to outside. Due to this difference in concentration, potassium ions tend to diffuse from inside the cell to the outside (down their concentration gradient). This movement is driven by the principle of diffusion, which seeks to equalize concentrations on both sides of the membrane.
- Electrical Gradient: The electrical gradient, on the other hand, is influenced by the charge distribution across the membrane. At rest, the inside of the neuron is more negative compared to the outside. Potassium ions, which are positively charged, are attracted to the negatively charged interior of the cell. This creates an inward force, pulling potassium ions back into the cell.
These two forces work in opposition. The chemical gradient pushes potassium ions outward (from high to low concentration), while the electrical gradient pulls potassium ions inward (due to the negative interior of the cell). The result is a balance between these two forces, which helps establish the resting membrane potential of the neuron. At equilibrium (which is near the potassium equilibrium potential), the movement of potassium ions in and out of the cell is balanced, and there is no net movement.
In summary, the movement of potassium is controlled by a combination of these gradients, with the chemical gradient pushing potassium ions out of the cell and the electrical gradient pulling them back in.