A group of neurons expresses a pump which actively transports Vz2- into the cell, and also expresses a limited number of Vz2- leak channels in the cell membrane. How would resting membrane potential change in this scenario compared to a “standard” neuron?

Question

BlackTom AI · Accepted Answer

Resting membrane potential is set by the balance of ionic concentration gradients and membrane permeabilities; increasing intracellular negative charge and limiting its leak will hyperpolarize the cell (make the inside more negative).

1) Relevant concepts:
- Resting potential arises because selective permeabilities (primarily K+ leak channels) and active transport create unequal ion distributions; potential is the voltage that balances chemical gradients.
- Electrogenic transport (movement of net charge) changes membrane voltage directly.
- Membrane leak channels determine how easily a pumped gradient dissipates; low permeability prevents rapid equilibration.

2) Step-by-step reasoning:
- The described pump actively transports Vz2- (a divalent anion) into the cytoplasm. That increases net negative charge inside relative to outside.
- Because this transport brings net negative charge across the membrane, it is electrogenic and immediately contributes to a more negative inside potential.
- The cell has only a limited number of Vz2- leak channels, so Vz2- cannot readily diffuse back out to neutralize the added negative charge. Low permeability means the newly established anionic gradient persists.
- The membrane potential will therefore shift until the electrical gradient opposes further net influx; that new equilibrium is at a more negative voltage than the “standard” neuron.

3) Intermediate/calculation-type logic:
- For illustration: a typical neuron rests around −65 to −70 mV. Adding net negative charge inside (and preventing its leak) drives the potential toward a larger negative value (e.g., −80 mV or more), i.e., hyperpolarization. No numeric constants needed to see the directional change.

4) Why the correct answer is correct:
- Because the pump increases intracellular negative charge and leak pathways are limited, the inside becomes relatively more negative than usual, so resting membrane potential becomes more negative.

5) Why other options are incorrect:
- “More positive” would require either loss of intracellular negative charge or net influx of positive charge, neither of which occurs here.
- “No change” would require rapid equilibration through high permeability or compensatory currents; limited leak channels prevent that, so a change does occur.

Conclusion: The resting membrane potential becomes more negative (hyperpolarized), confirming answer b. More negative.

A group of neurons expresses a pump which actively transports Vz2- into the cell, and also expresses a limited number of Vz2- leak channels in the cell membrane. How would resting membrane potential change in this scenario compared to a “standard” neuron?单项选择题

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