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Current time:0:00Total duration:7:49

From terpenes to steroids part 1: Terpenes

Video transcript

all right 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 and so to accomplish that I really need to start by introducing you to terpenes and terpenoids but it refers to a class of lipid molecules that are made of a repeating distinct set of carbon atoms called isoprene and so I'll draw in that carbon unit called isoprene an isoprene has this really distinct structure for carbon chain together so one two three four with the fifth carbon branching off of 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 ten carbons and we call that a monoterpene and and one of my favorite monoterpenes right now is 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 and that would give you three units of isoprene and and we caught a sequitur pean and one example of a sequitur pean 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 and so really you can just keep adding these isoprene units and making larger and larger molecules and so I'll just go ahead and make a chart here and remember monoterpenes had two isoprene units and sequitur peens 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 twenty 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 sester terpene and you could just keep going and you could have six isoprene units for 30 total carbons and that would be a triterpene because because essentially now we've got three monoterpenes and then if you added a another monoterpene to that you'd have a tetra terpene n' and that would have 40 carbons and eight isoprene units but really this could keep going and and we could keep adding isoprene units and we'd find lots of nice plant oils that we make and vitamins but that unfortunately is not our goal today we're still talking about steroids so I'm in a shift to how our body uses these isoprene building blocks to create the chemicals that it needs and that's the that's a process that's called biosynthesis so let me clear some room so that we can talk about biosynthesis and 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 and so that's pyrophosphate this this green area is pyrophosphate and you probably won't be expected to know too much about pyrophosphate but 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 the 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 aloe pyrophosphate and isopentyl pyrophosphate and I've just shortened the the higher phosphate 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 and 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 a 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 that 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 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 okay just wanted to just wanted to make sure that I actually got thirty carbon molecules in there and I think I did and that is that is scaling it was important for me to get to squealing because this is the molecule that forms the base of all of the steroid hormones that our body