Question: One of the following types of transport through membranes does NOT exist: 
 Options:  <1> Ion transport facilitated by ionophore (against electrochemical gradient). <2> Facilitated diffusion (in favor of electrochemical gradient) <3> Primary active transport (against electrochemical gradient). <4> Ionic channel (in favor of electrochemical gradient). <5> Simple diffusion (in favor of concentration gradient).
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