In this video, we're going to introduce two other classes of lipids, the steroids and waxes. Steroids are a complex class of lipids that look very different from the other lipids that we've talked about so far in our course. This is because steroids are not made of fatty acids. Instead, these steroids are going to be lipids that are made of four fused carbon ring structures. Now, the molecule cholesterol is actually a classic example of a steroid. You may have heard of this molecule cholesterol before because it is a common steroid that is important for the structure of animal cell membranes.
If we take a look at our example image down below, notice that the molecule we're showing you here on the left is cholesterol, which again is a classic example of a steroid. Again, steroids have four fused carbon ring structures, and note that each of the four fused carbon ring structures are numbered in this cholesterol molecule down below 1, 2, 3, and 4. Cholesterol is critical to the structure of animal cell membranes, and on the right side of the image, notice we're showing you an animal cell membrane which we know from our previous lesson videos that cell membranes are predominantly going to be made of phospholipid molecules; so you can see these phospholipids here in this membrane. However, embedded between this phospholipid bilayer, you'll find these cholesterol molecules in animal cell membranes.
Later in our course, we'll talk more about the exact role of cholesterol in the cell membrane but for now, you should just note that steroids are another class of lipid and cholesterol is an example of a steroid. Now, the waxes again are a second class of lipid and they are going to be predominantly used for protection purposes as well as the prevention of water loss.
Notice over here on the right side of our image what we're showing you is a structure of a molecule that represents a wax. This molecule right here is actually a structure that makes up beeswax and that's why we are showing you a bee over here. Notice that this wax molecule is going to be made up of a fatty acid and you can see the fatty acid is right here, and it is also going to be made up of a long chain, a molecule that used to be a long chain alcohol group, and at this end right here, this used to be an alcohol group with a hydroxyl group there. But after combining with this fatty acid, that alcohol group is no longer there. But this here concludes our brief lesson on steroids and waxes, these other two classes of lipids, and we'll be able to get some practice applying these concepts as we move forward. So I'll see you all in our next video.
