Transcription
All right, steroids are another type of lipid. Steroids look nothing like triglycerides, which is another form of lipid that we've learned about. And like I said before, lipids don't have this pattern that you see recurring. They're just all this; they're a grab bag bunch of molecules that are grouped together simply because of their hydrophobic or water-avoiding nature.
So, this does not look anything like a triglyceride, and that's okay. This is cholesterol. So, this is the same molecule that you hear about in your diet. Cholesterol is a type of steroid. So, steroids, and cholesterol is like the base steroid. You start with cholesterol, and then you build it into other kinds of things.
So, you need to be able to recognize this, and there's nothing really that quite looks like it. It's sort of a one-of-a-kind molecule. And so, from cholesterol, which we can get from our diet, or as animals, as mammals, we can actually make cholesterol within ourselves as well. We can make anything we don't get from our diet; we can produce in our cells. You start with cholesterol, and then you can turn it into various things that you need.
You need several steroid hormones, vitamin A, vitamin D. These are vitamins that are kind of based off of cholesterol, so they're not exactly like this, but you kind of modify it a little bit to them to make the vitamin D. This molecule also, cholesterol, is found in your cell membranes, and it also is modified to make the steroid hormones, which is estrogen and testosterone.
So, these are all forms of steroids: cholesterol, vitamin D, estrogen, testosterone. They all follow this main pattern. So, if you look at the cholesterol here, you can see to turn cholesterol into estrogen, all I really do is like snip off this chain and add a different functional group. Or if I want to change this cholesterol into testosterone, I also snip off the chain, add a functional group, and put a carbonyl here instead of an OH. Right? So, these are all kind of like variations on a theme. You start with cholesterol, that's your base starting point, and then you modify it in different ways to create vitamin D, or estrogen, or testosterone.
Let's see. These are hydrophobic molecules, so there are very few partial charges on here, just like in the triglycerides. So, that explains why these molecules are classed as lipids, that is steroids.