Which Statement Summarizes How the 0

question 7

Multiple Choice

Which statement summarizes how the 0.3 nm selectivity filter of K_CS channels enables potassium to penetrate but not sodium or lithium?

• A) Because of their smaller diameter and charge, sodium and lithium ions interact strongly with carbonyl oxygens and effectively get stuck in the pore region and do not flow through the channel.
• B) Because their diameters exceed 0.3 nm, sodium and lithium are excluded on the basis of size.
• C) Carbonyl oxygens provide a surrogate environment that keeps potassium ions in aqueous solution while passing through the channel.
• D) Carbonyl oxygens provide a surrogate environment for dehydrated potassium ions in the selectivity filter that mimics the hydration energy of ions in solution.
• E) Carbonyl oxygens provide a surrogate environment for dehydrated sodium or lithium ions in the selectivity filter that mimics the hydration energy of ions in solution.

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