What is the structure of channel proteins?

Channel proteins are tubular shaped, acting as a passageway for the molecules to pass from one side of the membrane to the other. They are composed of multiple amino acid subunits that are identical to each other. The amino acid subunits are arranged in such a manner to form a hydrophilic region in the center. 

The subunits that face the hollow passageway are designed to facilitate the movement of the substances being transported by the channel protein. The amino acids that face the aqueous environment of the cell are hydrophilic in nature. The amino acids facing the hydrophobic tails in the transmembrane area of the protein are hydrophobic in nature.