Question

How do carrier proteins differ from channel proteins?

A) Only carrier proteins have a hydrophilic interior channel.
B) Only carrier proteins can facilitate net movement of a substance down its concentration gradient.
C) Only carrier proteins actually bind to the substance being transported.
D) Only carrier proteins are selective for one type of molecule.

Answer 1

Carrier proteins bind to and are selective for the substance they transport, changing shape to move the substance across the membrane, unlike channel proteins which form pores and do not bind specifically to the substances they transport.

Step-by-step explanation:

Carrier proteins differ from channel proteins mainly because only carrier proteins actually bind to the substance being transported (C). Carrier proteins are highly selective and function by changing shape after binding their specific cargo, while channel proteins form pores through which molecules can pass based on size and charge, without specific binding.

Channel proteins facilitate rapid transport, allowing tens of millions of molecules per second to pass through, whereas carrier proteins transport substances at a slower rate, moving about a thousand to a million molecules per second.

Unlike channel proteins, the action of carrier proteins results in a change of the protein's shape, transporting substances across the membrane this way.