Transmembrane protein
A transmembrane protein (TP) is a type of membrane protein spanning the entirety of the biological membrane to which it is permanently attached. That is, transmembrane proteins span from one side of a membrane through to the other side of the membrane. The firm attachment of TP to the biological membrane is aided by a special class of membrane lipids, called annular lipid shells. Many TPs function as gateways or “loading docks” to deny or permit the transport of specific substances across the biological membrane, to get into the cell, or out of the cell as in the case of waste byproducts. As a response to the shape of certain molecules these “freight handling,” TPs may have special ways of folding up or bending that will move a substance through the biological membrane.