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GATE 2024 BM – Question 13

Mammalian Cell Biology, Human Anatomy and Physiology · Nervous System · 1 mark · Multiple choice

The source discusses the sodium–potassium pump in restoring neuronal ionic conditions after activity. Which active-transport statement is true?

  1. Three Na⁺ out for two K⁺ in
  2. Three Na⁺ in for two K⁺ out
  3. Two Na⁺ out for three K⁺ in
  4. Na⁺:K⁺ transport ratio always one

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Correct answer: (A) Three Na⁺ out for two K⁺ in

Explanation

Each Na⁺/K⁺-ATPase cycle exports three sodium ions and imports two potassium ions, using ATP and producing net outward positive charge. Thus A. Rapid action-potential repolarization itself is mainly through ion-channel currents; the pump maintains/restores the underlying gradients rather than being the sole rapid repolarizing mechanism.

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