When considering membrane transport, what is a transporter?

Transporters are the integral membrane proteins that serve to move the substances across the membrane.

Explanation:

Transporters are the membrane proteins that serve to move specific ions or molecules across the lipid bilayer. These are the integral membrane proteins. Transporters include carriers, channels, pumps, etc. Channels are the integral membrane proteins that serve to provide a pathway for transport of charged and/or polar substances that otherwise can not cross the non-polar core of the lipid bilayer.

Pumps are involved in the active transport of substances against the concentration gradient and use the energy of ATP hydrolysis. Some of the examples of transporters are voltage-gated ion channels, GLUT1 glucose transporter, F₀F₁ ATPase proton pump, etc.