For Each of the Following Sentences, Fill in the Blanks

For each of the following sentences, fill in the blanks with the best word or phrase selected from the list below.Not all words or phrases will be used; each word or phrase should be used only once.
$\begin{array}{lll}\text { active } & \text { hydrophilic } & \text { noncovalent } \\\text { amino acid } & \text { hydrophobic } & \text { passive } \\\text { amphipathic } & \text { ion channels } & \text { transporter proteins }\end{array}$


A molecule moves down its concentration gradient by __________ transport, but requires __________ transport to move up its concentration gradient.Transporter proteins and ion channels function in membrane transport by providing a __________ pathway through the membrane for specific polar solutes or inorganic ions.__________ are highly selective in the solutes they transport, binding the solute at a specific site and changing conformation so as to transport the solute across the membrane.On the other hand, __________ discriminate between solutes mainly on the basis of size and electrical charge.