Final answer:
The sodium-potassium pump contributes to a net negative charge inside the cell by expelling more positive Na+ ions than it takes in K+ ions, creating a difference in charge across the cell membrane.
Step-by-step explanation:
The sodium-potassium pump does directly contribute to generating a stable net negative charge inside of the cell. This is because the pump works by moving three Na+ ions out of the cell and two K+ ions into the cell against their concentration gradients. As a result, there are more positive charges being expelled than taken in, which leads to a net loss of positive charges inside the cell and hence, a negative charge difference across the cell membrane.
The action of the sodium-potassium pump is an example of active transport, using ATP to fuel the process. This active transportation of ions also establishes a concentration gradient that is essential for various cellular processes, including the regulation of osmotic balance and the firing of neurons in nerve cells. Additionally, the cell membrane becomes impermeable to these ions, so the difference in charge is maintained, contributing to what is known as the membrane potential.