B Two classes of membrane transport proteins Carrier proteins are responsible for both the passive and the active transport. Channel proteins are only responsible for passive transport transported molecule channel○ carrier prote proter 8 lipid electrochemical bilayer gradient mple channel. cartier. diffusion mediated mediated diffusion diffusion PASSIVE TRANSPORT ACTIVE TRANSPORT (FACILITATED DIFFUSION)B. Two classes of membrane transport proteins ❖Carrier proteins are responsible for both the passive and the active transport. ❖Channel proteins are only responsible for passive transport