Bacteriorhodopsin is an integral bacterial membrane protein. As seen in Figure 10.15, the linear polypeptide chain of bacteriorhodopsin folds back and forth several times in the membrane to provide a channel through which protons move. Figure 10.16 shows that a plot of the hydrophobic tendency of amino acids in the protein parallels the regions embedded in the membrane. Thus, hydrophobic regions of the protein are embedded in the protein and hydrophilic regions are at the surfaces.