And that's exactly why it will not be able to pass across our phospholipid bilayer because it's simply too polar. Now let's move on to a transport known as active transport. So we saw that in passive diffusion and facilitate the fusion, in both cases, the molecules moved down the electrochemical gradient and so we needed no energy. In this case, in active transport, we see that we actually move the molecule against the electrochemical gradient. So in some cases, we need to move ions or molecules against their electrochemical gradient. And one example is the neuron cell that basically uses active transport to create an electrochemical gradient to allow the propagation of our action potential, our electrical signal.