Each channel protein is specific for each ion

Each channel protein acts as a gate which can open and close

CHANNEL PROTEINS

They open up spaces or pores (lined with polar groups) across the membrane and allow entry or exit of charged ions

CARRIER PROTEINS

They allow the diffusion of larger polar molecules such as sugars and amino acids

A molecule attaches to the carrier protein at its binding site this changes the shape of the protein and the molecule is delivered through the membrane