Now cholesterol looks like
a lanosterol, as you can see.
But you can also see that it is not a simple process
of getting from lanosterol to cholesterol.
This process requires 19 steps
to go from one to the other.
And this 19 step process
is very energy requiring
and demanding. So that
early regulation by the
HMG-CoA reductase is a
very important consideration.
Cholesterol if it accumulates, as
I noted, won't inhibit its own synthesis.
Now cholesterol is an
important component of membranes.
If we look at our brain, our
brain if we would dry the tissue down
contains 14% by weight of cholesterol.
Cholesterol is very important and it's one of the reasons
why our body needs and is using cholesterol; because,
we don't have it in our body simply that will
cause problem which it's also associated with.
So cholesterol in our body is there by three different
mechanisms. First, our cells can synthesize it, as I noted,
and it can also be stored in the body.
And the way the cholesterol is stored
this by linking it to a fatty acid and an extra bond
through the hydroxyl group on the lower left.
Then cholesterol can be called upon
and use in the body as necessary.
The third way in which cholesterol
in our body is through dietary means.
And it's those dietary means that can be big
variables in how much cholesterol a person gets in.
A person who has high cholesterol
when they talk to the doctor, the doctor will use
it take as a first step in trying to treat that
changing the dietary intake
of the person to see if they
can someway alter the cholesterol
level as a result of that.
For some people that's all it takes. For others
more aggressive means may be required.
Now, one of the reasons we worried about the
cholesterol is because it's implicated
in atherosclerosis. An atherosclerosis has
so obviously some very important implications
and monitoring cholesterol levels is a
very essential part of a modern health regime.
The cholesterol is the precursor of
steroid hormone and bile acids.
So the steroid hormones are made from
cholesterol as are the bile acids
and of course, as we will see, these
play important functions as well.
In last cholesterol, like
fat, is very water insoluble
which means that it can't just go in
the blood stream and travel freely.
Instead it must move in the blood stream through
what are called lipoprotein complexes.
And these lipoprotein complexes have names called LDLs,
IDLs, VLDLs and HDLs and the DL part
stands for density lipoprotein.
And the L, I, V, and H
stand for Low, Intermediate, Very low and High.
So, monitoring these as part of
a cholesterol monitoring scheme is
a very important consideration.
LDLs, as we will see, are considered the "bad"
cholesterol and there is a good reason for that.