In this case, we don't use energy, but we do need our protein because as in this case, we use sugar. Sugar is a large molecule. It's also very polar. 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.