A Potassium Channel Conducts K⁺ Ions Several Orders of Magnitude

question 31

Multiple Choice

A potassium channel conducts K⁺ ions several orders of magnitude better than Na⁺ ions, because …

• A) the Na⁺ ion is too large to pass through the channel pore.
• B) the hydrated Na⁺ ion occupies a larger volume compared to the hydrated K⁺ ion, and is too large to pass through the channel pore.
• C) the Na⁺ ion is too small to interact with the channel in a way that facilitates the loss of water from the ion.
• D) the Na⁺ ion cannot bind to the high-affinity K⁺-binding sites in the channel pore.

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