Question at position 19 What membrane proteins are active during graph section labeled “A”?Membrane proteins are inactiveLigand-gated channelsVoltage-gated channelsNa+/K+ transporterClear my selection单项选择题
A
Membrane proteins are inactive
B
Ligand-gated channels
C
Voltage-gated channels
D
Na+/K+ transporter

Question

Question at position 19 What membrane proteins are active during graph section labeled “A”?Membrane proteins are inactiveLigand-gated channelsVoltage-gated channelsNa+/K+ transporterClear my selection单项选择题

A

Membrane proteins are inactive

B

Ligand-gated channels

C

Voltage-gated channels

D

Na+/K+ transporter

BlackTom AI · Accepted Answer

Resting membrane potential is maintained primarily by the Na+/K+ ATPase (Na+/K+ transporter), so that transporter is active during section A.

1) Relevant knowledge points and concepts
- Neurons display phases of an action potential: resting potential, depolarization, repolarization, hyperpolarization, and return to rest.
- The resting membrane potential (~−70 to −80 mV on the graph at A) is set by ion concentration gradients and selective permeability (K+ leak channels) and is actively maintained by the Na+/K+ ATPase.
- Voltage-gated Na+ and K+ channels open/close during the spike (B–C and D), while ligand-gated channels require neurotransmitter binding.

2) Step-by-step reasoning
- Identify A on the graph: membrane potential near −70 to −80 mV before the spike → this is the resting state.
- Which membrane proteins function at rest? Passive K+ leak channels are open, and the Na+/K+ ATPase continuously pumps ions to preserve gradients.
- Among the answer choices, the Na+/K+ transporter is the active protein that continuously operates at rest.

3) Simple quantitative detail (intermediate step)
- The Na+/K+ ATPase moves 3 Na+ out and 2 K+ in per ATP hydrolyzed → net export of one positive charge per cycle, contributing to the negative resting potential.

4) Why the correct answer is correct
- The Na+/K+ transporter is constitutively active to maintain concentration gradients and the resting potential shown at A. It functions independently of the action potential spike.

5) Why other options are incorrect
- "Membrane proteins are inactive": incorrect because the Na+/K+ pump and leak channels are active at rest.
- "Ligand-gated channels": require neurotransmitter binding; not generally active at baseline in this graph.
- "Voltage-gated channels": these are closed/inactive at resting potential and only open during depolarization (B–C).

6) Conclusion
- Therefore the correct active membrane protein during graph section A is the Na+/K+ transporter, matching the provided answer.

Question at position 19 What membrane proteins are active during graph section labeled “A”?Membrane proteins are inactiveLigand-gated channelsVoltage-gated channelsNa+/K+ transporterClear my selection单项选择题

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