So even though cholesterol is so big, because it has no charge and essentially not polar at all, it will not have any problem moving across that cell membrane. Now, let's discuss a special type of cell transport known as passive diffusion. This is basically what we just discussed. So certain molecules, such as cholesterol and water can travel through the cell membrane down its electrochemical gradient, much like a ball falls down the gravitational potential gradient. This process does not require any use of energy in the form of ATP, nor does it actually require the use of an integral protein. And this process is known as passive diffusion.