Which of the following appears to contribute to the selectivity filter of the potassium channel?
- The channel pore narrows to fit the size of a non-hydrated potassium ion.
- Cations such as cesium are too large to pass through the pore.
- Cations such as sodium are too small to be dehydrated at the pore filter.
- All of the above
- None of the above
Answer: 4