Some transporters, such as certain members of the SLC family, are referred to as 'carriers'; however GO uses carrier with a different meaning: a carrier binds to and transports the substance (see GO:0140104 molecular carrier activity), whereas a transporter forms some pore that allows the passing of molecules.

transporter activity

GO:0005215

Enables the directed movement of substances (such as macromolecules, small molecules, ions) into, out of or within a cell, accross or in between cells.

molecular_function

GO:0005215

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carrier

GO:0005478