Some channel proteins are gated and change conformation to allow or prevent diffusion
Ligand-gated channels are controlled by the binding of signal molecules, and voltage-gated channels are controlled by changes in ion concentration
Transporter proteins bind to the specific substance to be transported and undergo a conformational change to transfer the solute across the membrane
Active transport uses pump proteins that transfer substances across the membrane against their concentration gradient
A source of metabolic energy is required for active transport
Some active transport proteins hydrolyse ATP directly to provide the energy for the conformational change required to move substances across the membrane