In this video, we're going to talk about simple and facilitated diffusion. Both simple diffusion and facilitated diffusion are types of passive transport, which means that the transport across the membrane occurs passively without any energy input whatsoever. There's absolutely no energy involved with passive transport, which means there's no energy involved with either simple or facilitated diffusion. Also, recall from our previous lesson videos that the reason passive transport requires no energy is that molecules are going to be transported down their concentration gradients, from areas of high concentration down to areas of low concentration, and that's why no energy is required. Simple diffusion, as its name implies, is quite simple and involves the direct diffusion of small uncharged molecules directly through the cell membrane, squeezing through between the phospholipids to get from one side of the membrane to the other, down its concentration gradient with no energy whatsoever.
Now, facilitated diffusion, on the other hand, is non-energetic diffusion. Non-energetic meaning that no energy is involved because it's passive transport. Instead of diffusing small uncharged molecules, typically facilitated diffusion transports charged molecules. But as its name implies, facilitated diffusion is facilitated by a transport protein. So, facilitated diffusion requires facilitation by a transport protein, whereas simple diffusion does not require any facilitation whatsoever.
Let's take a look at our image down below to get a better understanding of this. Notice that over here on the left-hand side, we're showing you a snippet of our map here where you can see that passive transport, which requires absolutely no energy input whatsoever, includes both simple diffusion and facilitated diffusion. Simple diffusion is straightforward. It requires no facilitation from a protein, so no protein is involved with simple diffusion. Whereas facilitated diffusion, the transportation involves a transport protein, which facilitates this diffusion.
Over here on this half of the image, we're showing you simple diffusion, which allows small uncharged molecules to simply diffuse directly through the membrane. These molecules here are uncharged and small enough to squeeze their way between the phospholipids and get to the other side of the membrane from an area of high concentration down to an area of low concentration. Because it's going from high concentration to low concentration down the concentration gradient, no energy is required for this type of transport, simple diffusion. Over here on the right-hand side of this image, notice that we're showing you facilitated diffusion.
Facilitated diffusion also transports molecules down their concentration gradients from an area of high concentration down to an area of low concentration, which is why no energy is required. No energy is needed for simple diffusion, and no energy is needed for facilitated diffusion. The differences are that facilitated diffusion mainly transports ions, or in other words, charged molecules. Whereas simple diffusion only occurs with small uncharged molecules, not with ions. If ions want to get to the other side of the membrane, they'll need some facilitation by a transport protein.
This protein that you see right here embedded in the membrane is creating a channel, basically a tunnel through the membrane, allowing these ions, these charged molecules, to diffuse down their concentration gradients across the membrane. A protein is involved, but no energy is needed because the molecules move from high concentration to low concentration. And so, this concludes our introduction to simple and facilitated diffusion, and we'll get to learn more and more about these processes as we move forward in our course. So, I'll see you in our next video.