Due to the nature of amphotericity and the conformation of plasma membrane, large or ionic molecules can not permeate through plasma membrane freely. To help with those transportations, protein involved transports are adopted. One of which is active transport, that uses energy to move substrates against electrochemical gradient. Among many active transport cases, sodium potassium transportation has been most widely studied for it is expressed in virtually all cells of higher organisms (Austgen 2003).
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