Final answer:
The fact that the potassium equilibrium potential is close to the resting membrane potential signifies that K+ ions critically influence the resting negative charge inside the neuron due to their concentration gradient and the selective permeability of the membrane to these ions.
Step-by-step explanation:
The fact that the equilibrium potential for K+ is very close to the resting membrane potential indicates that potassium ions play a key role in establishing and maintaining the resting membrane potential of cells. In neurons, the resting membrane potential is approximately -70 mV, and this is mainly due to the difference in concentration of K+ ions inside and outside the cell. Potassium ions have a higher concentration inside the neuron compared to outside, and because potassium channels are open most of the time, they can leave the cell following their gradient, leaving behind a negative charge.
This negative charge inside the neuron compared to the outside environment is crucial for nerve impulse conduction and muscle contraction. The sodium-potassium pump also contributes to this resting potential by moving K+ ions into the cell and Na+ ions out of the cell, although at a different rate, further contributing to the charge difference across the cell membrane.
Since potassium channels are open more frequently than sodium channels, the inner cellular environment tends to become more negatively charged due to the net efflux of positively charged ions. This results in the resting membrane potential being closely aligned with the potassium equilibrium potential.