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From terpenes to steroids part 1: Terpenes

Steroids have to come from somewhere, right? Let's learn about the carbon building blocks with which steroids are made. By Ryan Patton. . Created by Ryan Scott Patton.

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  • leafers ultimate style avatar for user royTP7
    It looks like the dimethyl allyl pyrophosphate and isopentenyl pyrophosphate are each missing one carbon molecule in their structure.
    (21 votes)
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  • starky ultimate style avatar for user ♪♫  Viola  ♫♪
    Are terpenes and terpenoids the same?
    (4 votes)
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    • duskpin ultimate style avatar for user Medical  Mermaid
      They are very similar, but there is a slight difference according to my book. Terpenes are a class of lipids that are build from isoprenes, while terpenoids are derivatives of terpenes that have undergone some sort of reaction, such as oxidation or rearrangement. So terpenoids are terpenes, but just with some slight modifications.

      Hope that helps :)
      (13 votes)
  • blobby green style avatar for user Martin Steckiewicz
    I'm pretty sure that students should know some details about pyrophosphate. One major detail is that its hydrolysis into two inorganic phosphates prevents many biochemical reverse reactions from occurring like in the polymerization reaction of DNA.
    (9 votes)
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  • starky ultimate style avatar for user Damusch
    I can´t finde the gingemolecule anywhere. I think it´s misleading to draw wrong molecules!
    (1 vote)
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    • leafers tree style avatar for user Leoriera88
      I was confused as well, but now i see that several of the main therapeutic compounds found in Ginger have a sesquiterpene structure.
      Look up the structures for Gingerol, Shogaol, and Zingerone. Put them together and you get 3 isoterpenes.
      (8 votes)
  • blobby green style avatar for user mattiawruble
    at , when two 4 carbon molecules isoprene react, the product drawn has 10 crbons. I'm assuming that the reactants should have 5 carbons each
    (3 votes)
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  • mr pants teal style avatar for user smart2start1
    At he was writing out the chart of 'terpenes' and I noticed that it went from triterpine with 30 carbons, to tetraterpine with 40 carbon. Is there anything in between them with 35 carbons?
    (3 votes)
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  • blobby green style avatar for user zvigoldman96
    At , what is a 'leaving group'?
    (2 votes)
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  • aqualine seed style avatar for user Jorge A. Garcia Lugo
    I don't get how it is an isopentyl and dimethyl, respectively. For the isopentyl I only see 4 carbon atoms.
    (3 votes)
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  • blobby green style avatar for user rmb21457
    What is the difference between upregulatio ANF downregulation
    (2 votes)
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  • duskpin ultimate style avatar for user Medha_V
    At , when pyrophosphate is being drawn, what are those things above two of the oxygen?
    (1 vote)
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    • leafers sapling style avatar for user Sarah
      Those represent the formal negative charge on O. The oxygen atom normally has 6 valence electrons but O atoms with only one bond to another atom have 7 (6 - 7 = -1). Notice that all the oxygen atoms with two bonds have no formal charge, because they have 6 valence electrons (6 - 6 = 0). The symbol he used to represent -1 formal charge is a negative sign in a circle, like this (-). Google may help you understand more about formal charge if you're still confused!
      (1 vote)

Video transcript

In previous videos, I introduced steroids to you as one example of the chemical messages that our body parts use to communicate with each other. And we call those chemical messages hormones, but I haven't really gotten to tell you all about steroids, and where they come from and how they're made, and that's what I want to do today. To accomplish that, I really need to start by introducing you to terpenes. Terpene might not be the most familiar of words, but it refers to a class of lipid molecules that are made of a repeating distinct set of carbon atoms called isoprene. So I'll draw in that carbon unit called isoprene. Isoprene has this really distinct structure of four carbons chained together-- one, two, three, four-- with a fifth carbon branching off of one of the middle carbons. And this five carbon unit repeats to build larger and larger molecules. And so as two five carbon isoprenes come together, you get a molecule that has 10 carbons. And we call that a monoterpene. And one of my favorite monoterpenes right now is menthol, which looks like this. And this little guy is super helpful to me right now, because I've had a pretty rough cough for the past week, and my cough drops are filled with menthol. And then if you add one more isoprene, you'd have 15 carbons. And that would give you three units of isoprene. Supreme And we'd call it a sequiterpene. And one example of a sequiterpene is ginger. And ginger looks like this. But you can see that ginger is made up of three isoprene units, and it fills up gingersnap cookies, and those are my favorite types of cookies. Really, you can just keep adding these isoprene units and making larger and larger molecules, so I'll just go ahead and make a chart here. Remember, monoterpenes had two isoprene units, and sequiterpenes had three isoprene units. And if you added another isoprene unit to that, you'd have a diterpene, and it would have four isoprene units, making 20 carbons. And it's called a diterpene now because it's really just two monoterpenes put together. And then you could add another one, and that would give us five. And five isoprenes for 25 carbons, and that would be a sesterterpene. And you could just keep going. And you could have six isoprene units for 30 total carbons, and that would be a triterpene. Because essentially now we've got three monoterpenes. And then, if you added another monoterpene to that, you'd have a tetraterpene, and that would have 40 carbons and eight isoprene units. But really, this could keep going, and we could keep adding isoprene units. And we'd find lots of nice plant oils that we'd make and vitamins. But that, unfortunately, is not our goal today. We're still talking about steroids. I'm going to shift to how our body uses these isoprene building blocks to create the chemicals that it needs. And that's a process that's called biosynthesis. So let me clear some room so that we can talk about biosynthesis. In biosynthesis, our body starts off with isoprene bound to something called pyrophosphate, which looks something like this. And I'm going to use the letter R to represent that isoprene unit for now. Just so I can really show you what pyrophosphate looks like. So that's pyrophosphate. This green area is pyrophosphate. And you probably won't be expected to know too much about pyrophosphate. But what you should know is that it's a really weak base, which makes it a good leaving group in organic chemistry, and that's the important part. Because for the reaction that our body uses to build with these blocks of isoprene, it needs a good leaving group, and that's pyrophosphate. And our body really begins with two different isoprene pyrophosphates, and they're found in nearly all living organisms. And those are dimethyl allyl pyrophosphate and isopentyl pyrophosphate. I've just shortened the pyrophosphate to OPP because that's what most textbooks abbreviate it as, and it saves quite a bit of time. But I will go ahead and write out the names of these, just so I don't confuse you too badly. And those names make pretty good sense if you've practiced naming carbon molecules in, say, an organic chemistry class or something. But they probably sound like a foreign language if you haven't. So let's not get too hung up on them here, because they don't help us much with the concept anyway. But what happens is the electrons of one pi bond act like a nucleophile, and they attack this carbon, allowing the pyrophosphate to leave. And that results in a 10 carbon molecule called geranyl pyrophosphate. And so that's geranyl pyrophosphate. And then that process might happen again, leading to a 15 carbon farnesyl pyrophosphate. And forgive me if I'm butchering the pronunciation, but I'll draw it in. That's farnesyl pyrophosphate. And then as these chemical reactions continue, our body eventually produces a triterpene, or if you remember, that's a 30 carbon molecule made of six isoprene units. And that triterpene is called squalene. So let me draw that in. OK, I just wanted to make sure that I actually got 30 carbon molecules in there, and I think I did. And that is squalene. It was important for me to get to squalene because this is the molecule the forms the basis of all of the steroid hormones that our body--