Final answer:
The resting membrane potential is usually -70 mV, mainly influenced by the differential distribution of potassium and sodium ions across the cell membrane. The sodium-potassium ATPase contributes to this by actively moving ions against their concentration gradients. The equilibrium potentials are specific voltages where ionic movements balance out.
Step-by-step explanation:
The resting membrane potential is typically measured at about -70 mV, with variations depending on the cell type. This electrical charge difference across the cell membrane is crucial for functions such as the conduction of nerve impulses in neurons. The resting membrane potential arises from the selective permeability of the cell membrane to ions, primarily due to potassium (K+) and sodium (Na+).
Potassium ions tend to move out of the cell via potassium leakage channels, leaving behind a negative charge due to their higher internal concentration. Conversely, sodium ions have a higher concentration outside the cell, but they cannot readily enter due to few sodium leakage channels. The sodium-potassium ATPase, or pump, uses energy to move 2 K+ ions into the cell and 3 Na+ ions out, further contributing to the membrane's potential. This process results in a net loss of positive charge from the cell, thus maintaining its negativity.
The equilibrium potentials for Na+ and K+ are the specific membrane voltages at which the net flow of these respective ions stops, due to the balance of concentration gradients and electrical gradients. While not explicitly provided in the question, they can be calculated using the Nernst equation with known ion concentrations inside and outside of the cell.