At a later stage in the reaction cycle, the phosphate is released by hydrolysis. Introduction to Ion Channels Channels cycle between open and closed conformations. When open, a channel provides a continuous pathway through the bilayer . Whereas carriers transport only one or a few ions or molecules per conformational cycle, many ions flow through a channel each time it opens. Thus transport rates are higher for channels than for carriers.
Gramicidin acts as a channel.
It is an unusual peptide, with alternating D and L amino acids. The molecule can assume other conformations in organic solvents, including double helical structures. The outer surface of the gramicidin dimer, which interacts with the core of the lipid bilayer, is hydrophobic. Ions pass through the more polar lumen of the helix. Drag the image to view the channel from the side, and down its axis.