Difficulty: Easy

Average Score: 100%

What happens to the gates of voltage-gated sodium ion channels when the cell is at rest?

Rationale

The activation gate is closed, while the inactivation gate is open.

At rest, voltage-gated sodium ion channels maintain a state where the activation gate is closed, preventing sodium ions from entering the cell, while the inactivation gate remains open, allowing for potential activation upon depolarization. This configuration is critical for maintaining the resting membrane potential and preparing the channel for rapid response during action potentials.

A (The activation gate is closed, while the inactivation gate is open.) CORRECT

This statement accurately describes the state of voltage-gated sodium channels at rest. The closed activation gate prevents sodium ions from entering the cell, while the open inactivation gate allows the channel to be ready for activation when the membrane potential changes. This arrangement is essential for the proper functioning of action potentials in excitable cells.

B (The activation gate, as well as the inactivation gate, is closed.) YOUR ANSWER

If both gates were closed, the sodium channel would be entirely inactive, preventing any potential for depolarization. This state does not occur at rest, as the inactivation gate must be open to allow the channel to respond appropriately to depolarizing stimuli.

C (The activation gate is open, while the inactivation gate is closed.) YOUR ANSWER

In this scenario, sodium ions would flow freely into the cell, which is not the case at rest. The open activation gate indicates that the channel is already activated, leading to depolarization, which contradicts the resting state of the cell.

D (The activation gate, as well as the inactivation gate, is open.) YOUR ANSWER

If both gates were open, the sodium channel would be in a continuously activated state, allowing excessive sodium influx, which would destabilize the resting potential and prevent the cell from returning to its resting state after depolarization.

Conclusion

At rest, the configuration of voltage-gated sodium ion channels is crucial for cellular function. The activation gate being closed while the inactivation gate is open ensures that the channels are prepared for activation upon depolarization, preserving the integrity of the resting membrane potential. Understanding this mechanism is vital for comprehending how neurons and muscle cells generate and propagate action potentials.

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