Now that the light's at the end of the tunnel a little bit,
I'm going to move a little bit more
quickly through these reactions.
So let me just copy and paste here.
I'm going to clear a little bit more space.
And so the body takes squalene, and through a series
of ring-closing, or cyclization reactions,
it makes cholesterol.
And we consume some cholesterol in our diet,
but our body also completes this reaction in the liver.
So our body takes squalene and turns it
into cholesterol in the liver.
And cholesterol travels through our blood
and it lives in the inside of cells and on their surfaces.
In the case of endocrine organs that
use steroid hormones to communicate,
cholesterol can actually be altered
to form the very characteristic steroid backbone.
So let me draw that.
So these are the four characteristic rings
of the steroid backbone.
As you can see, we are a really long way off,
at this point, from the very beginning
place that we started, which was that isoprene unit.
Now that I've dragged you all the way from isoprene
to the steroid backbone, I figured
it was only fair that I showed you that this actually
happens in your body, and there are actual steroids
floating around your blood.
I mentioned before that there are two important classes
of steroid hormones in the body, and those are the sex hormones
and the adrenal cortex steroids.
With the sex hormones, I mentioned before estrogens,
and we have estrasdiol and estrone.
And you can see their steroid backbone.
And those are predominantly made in the ovaries,
and they're principally involved in secondary sex
characteristics for females.
And we have progesterone.
It's the pregnancy hormone.
It's involved in prepping the uterus,
and it's also involved in maintaining
a healthy pregnancy.
And then we have androgens.
And we have testosterone and androsterone.
And similarly to the estrogens, those
regulate the secondary sex characteristics, but more so
in males.
And they're predominantly made in the testes.
Moving over to the adrenal cortex steroids,
we have cortisone and cortisol.
And those are the body's stress hormones,
so they have a lot of the effects from anti-inflammatory
to increasing carbohydrate metabolism.
We also have aldosterone.
Aldosterone is one of the main hormones that
regulates our body's blood pressure and the fluid volume.
And so I hope all these images make steroids a little bit more
familiar to you, now that you've seen the classic backbone,
and you know how to make it.
Maybe the next time you find yourself enjoying the soothing
relief of a menthol cough drop or a savory and delicious
ginger snap cookie, you'll think about the countless number
of terpenes that you're enjoying.