And so in this case, we do not use any type of energy. But in the case of active transport, as we describe in section three, we basically use we expend an ATP molecule to basically move our sodium as well as the potassium, which normally cannot move through the phospholipid bilier because they have positive charge. We use this type of integral protein to basically move these molecules against our electrochemical gradient. So whenever we move things against electrochemical gradient, that requires proteins as well as energy. But whenever we move things down the electrochemical gradient, that does not require any energy whatsoever. In some cases, we do not even require our integral protein, as the case is with passive diffusion.