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 otein protein lipid electrochemical bilayer gradient ○○ simple hannel carrie diffusion mediated mediated L diffusion diffusion PASSIVE TRANSPORT ACTIVE TRANSPORT (FACILITATED DIFFUSIONB. 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