Transmembrane protein
A transmembrane protein is an amphiphatic protein with hydrophilic and hydrophobic regions which span the lipid bilayer. The hydrophobic regions of a transmembrane protein are buried inside the lipid bilayer whereas its hydrophillic regions are exposed on the outside[1]. These proteins can either be 'single-pass' meaning it crosses the membrane once or 'multipass' and therefore crosses the bilayer more than once. Transmembrane proteins are usually either a single alpha helix, multiple alpha helices or a beta sheet that has been rolled and is referred to as a beta barrel[2].