So what exactly is the difference between a proteoglycan and a glycoprotein? Well, in the case of glycoproteins, the sugar component makes up a much smaller percentage by mass of the biological molecule than compared to the proteoglycan. And this is the main difference between these two types of biological molecules. So glycoproteins are an important class of biological molecules that play a variety of different roles inside our cells and inside our body, as we'll see in future lectures. And they can be found along the cell membrane. They can also be found in the extracellular matrix.