Question

Which of these ions is actively transported through the cell membrane to establish a resting potential?

1) Na
2) Cl
3) Mg
4) Ca

Answer 1

The ion that is actively transported to establish a resting potential is Na+. The Na+/K+ pump moves Na+ out of the cell and K+ in, establishing the negative charge essential for the cell's resting state. Voltage-gated ion channels are indispensable for initiating action potentials.

Step-by-step explanation:

The ion that is actively transported across the cell membrane to establish a resting potential is sodium (Na+). Establishing a resting membrane potential is crucial for the function of nerve and muscle cells, and this potential is typically negative inside the cell compared to the outside. The sodium-potassium pump (Na+/K+ transporter) actively transports Na+ ions out of the cell and K+ ions into the cell, doing so in a ratio that contributes to the negative charge inside the cell, which is essential for the resting state of the cell.

Regarding the ions listed in the question:

1. Na+ is actively transported out of the cell.
2. Cl- ions play a role in balancing charges but are not typically pumped against a concentration gradient in the manner that Na+ is.
3. Mg2+ has functions within the body but is not primarily involved in generating the resting membrane potential.
4. Ca2+ is important for other cellular activities like muscle contraction, not for maintaining the resting potential.

It is impossible to trigger an action potential without voltage-gated ion channels because these channels are critical for the rapid influx of Na+ into the cell and K+ out of the cell, which changes the membrane potential and propagates the action potential along the neuron.