Since on the inner and outer surfaces of the membrane, a series of negatively charged amino acids are found, which increase the local concentration of cations. The path of the ions begins on the inner surface filled with water molecules where the ion can retain its hydration sphere. Two thirds of its interior in the membrane the inside of the channel narrows in the region of the selectivity filter, forcing the ion to separate from the water molecules. Oxygen atoms in the selectivity filter replace the water molecules in the K+ hydration sphere, forming a series of coordination spheres through which the ion moves. The preferential stabilization of K+ against Na+ is the basis of the ion selectivity of this filter.
Four people weigh a standard mass of 10.00 g on the same balance. The set of readings suggest measurements that are neither precise <span>nor accurate is the one with less mass</span>
