Answer to Question #238760 in Cell Biology for Mika

Question #238760

In class we are studying action potentials, repolarization, hyperpolarization, etc.

My teacher told us how once a certain membrane potential is reached and the action potential is fired, potassium channels open and potassium ions flood out of the axon, making it more negative and helping it reach resting potential again. My teacher said that the protein has to be "pumped" out using ATP because it is moving against the concentration gradient. However, looking online it seems like the potassium passes through voltage-gated potassium channels along/following the concentration gradient and therefore doesn't require energy. So does the potassium exiting the cell in repolarization require ATP or no? Does the potassium go through a "pump" or just voltage-gated ion channels?

Expert's answer

Does not require ATP

The repolarization phase usually returns the membrane potential back to the resting membrane potential. The efflux of potassium (K+) ions results in the falling phase of an action potential. After repolarization, the cell hyperpolarizes as it reaches resting membrane potential (−70 mV){in neuron −70 mV}.

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