Final answer:
Channel proteins facilitate specific and passive transport across the cell membrane, providing a hydrophilic pathway without interacting strongly with the solutes or undergoing conformational changes.
Step-by-step explanation:
In contrast to transporters, channel proteins in cellular membranes can only mediate passive transport. Channel proteins, such as aquaporins and ion channels, facilitate the movement of water and ions, respectively, across the cell membrane. This process is highly specific, as each channel is specific for the substance it transports. Moreover, channel proteins do not interact strongly with the solutes they transport and do not undergo a conformational change every time they transport a solute, unlike carrier proteins that change shape to move molecules across the membrane. Instead, channel proteins provide a hydrophilic passageway for the facilitated diffusion of polar compounds, avoiding interaction with the central nonpolar layer of the plasma membrane.