Final answer:
Channel proteins make a passageway for substances without shape change, while carrier proteins undergo shape change, transporting substances down a concentration gradient.
Step-by-step explanation:
The correct statement about channel and carrier proteins is: C) Channel and carrier proteins always move substances from the side of the membrane with the highest concentration to the side with the lowest concentration. Channel proteins facilitate the movement of substances across the membrane by forming an open passageway for the movement of specific ions or molecules without changing shape. On the other hand, carrier proteins bind to the substance they transport and undergo a shape change to move the substance across the membrane. This process generally occurs down a concentration gradient, meaning substances move from an area of higher concentration to an area of lower concentration, following the principles of diffusion.