>>11837894You mean the protein in op's picture right? Well, I guess it's sort of like a conduit, but it uses hydrogen instead of water. What is happening is that the cell has produced a gradient of h+ atoms on the outside of the membrane. The h+ atoms on the outside want to diffuse back into the membrane to eliminate the gradient and to lower the potential energy. The only way back in is though that protein on the membrane, and in order to pass through the protein, a GDP molecule must be bound to the protein converted to GTP. The energy to make GTP comes from hydrogen atoms passing though the membrane. The protein itself is defiantly a chain of amino acids, but again, proteins have many other functions other then just this. If you wanted to define a protein generally, then I'd say it's a chain of amino acids, that fold into a specific shape/shapes to carry out some function within the body.
