Question

Which of the following is true about the movement of ions across excitable living membranes?

1) Ions always move actively across membranes through leakage channels.
2) Some ions are prevented from moving down their concentration gradients by ATP-driven pumps.
3) Sodium gates in the membrane can open in response to electrical potential changes.
4) The bulk of the solutions inside a cell are negatively charged.

Answer 1

Sodium gates in the membrane can open in response to electrical potential changes, allowing the movement of sodium ions into the cell.

Step-by-step explanation:

The correct statement about the movement of ions across excitable living membranes is that sodium gates in the membrane can open in response to electrical potential changes. This means that when there is a change in the electrical potential across the membrane, the sodium gates can open, allowing the movement of sodium ions into the cell. This is an example of a gated ion channel opening in response to an electrical signal.

Among the other options, ions do not always move actively across membranes through leakage channels (option 1). Some ions are prevented from moving down their concentration gradients by ATP-driven pumps (option 2). The bulk of the solutions inside a cell are negatively charged due to the separation of charges across the plasma membrane, creating a negative membrane potential (option 4).