29. What happens to the gates of voltage-gated sodium ion channels when the cell is at rest?
Answer: A
The activation gate is closed, while the inactivation gate is open.
In a resting state, voltage-gated sodium ion channels have their activation gates closed, preventing sodium ions from entering the cell, while the inactivation gates remain open, allowing for potential activation in response to a depolarizing stimulus.
A) The activation gate is closed, while the inactivation gate is open.
This option accurately describes the state of voltage-gated sodium ion channels when a cell is at rest. In this state, the activation gate prevents sodium influx, which is crucial for maintaining the resting membrane potential, while the inactivation gate is not blocking the channel, leaving it ready for activation upon depolarization.
B) The activation gate, as well as the inactivation gate, is closed.
This option is incorrect because if both gates were closed, the channel would be completely inactive and unable to respond to depolarization. In reality, the inactivation gate remains open during resting potential, allowing the channel to be primed for activation.
C) The activation gate is open, while the inactivation gate is closed.
This option is also incorrect because during the resting state, the activation gate must be closed to prevent sodium influx. If the activation gate were open, sodium ions would flood into the cell, depolarizing the membrane rather than maintaining the resting potential.
D) The activation gate, as well as the inactivation gate, is open.
This option is incorrect as it suggests that the channel is fully activated, which would not occur at rest. Both gates being open would lead to a continuous influx of sodium ions, contradicting the conditions necessary for the cell to maintain its resting membrane potential.
Conclusion
Option A is definitively correct as it reflects the accurate configuration of voltage-gated sodium ion channels at rest, with the activation gate closed and the inactivation gate open. All other options incorrectly represent the gating mechanisms, which are essential for the proper function of action potentials in neurons.