Question

When more than one ion species (i.e., Na+ and K+) is present on both sides of the membrane, the chemical driving force acting on Na+ will include

A) all ions present.

B) the most concentrated ion only.

C) sodium only.

D) all negatively charged ions.

E) all positively charged ions

Answer 1

The chemical driving force for Na+ ions includes their concentration outside the cell and the negative charge inside. Meanwhile, the sodium-potassium pump further enhances this gradient by expelling more Na+ than it brings in K+.

Step-by-step explanation:

When considering the chemical driving forces for sodium (Na+) and potassium (K+) ions across a cell membrane, it's essential to consider both the concentration gradient and the electrical gradient, which together form the electrochemical gradient. Na+ ions are higher in concentration outside of the cell, while K+ ions are higher inside.

The cell membrane's semi-permeability allows these ions to move according to these gradients. In resting neurons, the diffusion of K+ out of the cell and the impermeability to Na+ leads to a buildup of negative charge inside the cell and positive charge outside. The sodium-potassium pump contributes to this by expelling more Na+ than it brings in K+, enhancing the negative charge inside the cell. The driving force for Na+ includes being attracted into the cell due to the higher concentration outside and the negative charge inside the cell.