Which type of passive transport uses proteins that change shape to move a target molecule through the membrane?

Diffusion is the process through which molecules move from an area of higher concentration to an area of lower concentration without the need for transport proteins. It does not involve any change in the shape of proteins; instead, molecules simply pass through the lipid bilayer or through channels if they are small enough. Therefore, diffusion does not utilize proteins that change shape to facilitate transport.

Channel proteins provide a passageway for specific ions or molecules to cross the membrane but do not undergo shape changes like carrier proteins. They allow for the facilitated diffusion of substances directly through a channel, rather than binding and altering their structure. As such, channel proteins operate differently than carrier proteins in transporting molecules.

This option incorrectly suggests that no answer is appropriate. Since carrier proteins specifically utilize shape changes to transport target molecules, this choice is not valid, as it ignores the correct function of carrier proteins in passive transport.