- [Instructor] 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 a
liver, and cholesterol
travels through our blood,
and it lives in the inside
of cells, and on their surfaces.
And 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.
And so these are the
four characteristic rings
of the steroid backbone.
And 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.
And so 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.
And so 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.
And so with the sex hormones,
I mentioned before estrogens.
And we had estradiol 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.
And it's kind of 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.
And then moving over to the
adrenal cortex steroids,
we have cortisone and cortisol,
and those are the body's stress hormones,
and so they have a lot of
effects, from anti-inflammatory
to increasing carbohydrate metabolism,
and then we also have aldosterone.
And 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, and maybe the next time
you find yourself enjoying
the soothing relief
of a menthol cough drop,
or a savory and delicious
gingersnap cookie, you'll think
about the countless number
of terpenes that you're enjoying.
