What is a characteristic feature of a carrier protein in a plasma membrane?

It exhibits specificity for a particular type of molecule .

Explanation:

Carrier proteins are a kind of transmembrane protein which helps in the transport of molecules across the cell membrane. Carrier proteins specifically binds to a particular and specific type of molecules and helps in their transportation.  

If they transport the molecules without the expenditure of energy then it is considered as facilitating diffusion and when they use ATP for transport it is called active transport.  

Inactive transport, molecules are moved against their concentration gradient and in facilitated diffusion, molecules are moved along their concentration gradient.

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