- [Voiceover] Lipids are one of the four
major macromolecules.
So lipids themselves though are insoluble in water.
If you mix oil and water, I don't care how much you
shake it around.
If you let it sit again, that oil will separate
from the water.
Now there are three major classes of lipids here.
And all three of 'em are gonna be insoluble in water.
We have the triglycerides.
Now these are mostly energy based, kind of help store
energy in your body.
We have the phospholipids.
These phopsholipids are important because they make up
a majority of your cell membrane.
So think of every cell in your body.
Those millions and millions and millions of cells.
The phospholipids are what make up the majority of
the membrane that covers them, which keeps them intact.
And then you have steroids.
These are gonna be a lipid that is based
on a ring structure.
Now these aren't the steroids you think of as
the illegal steroids from sports.
It's just steroids that everyone has in their body.
There are things like cholesterol, estrogen, testosterone.
Those are steroids.
So steroids, this particular type is a form of a lipid.
We'll start with the triglycerides.
Now more commonly, the triglycerides are known as fats,
or they're known as oils.
These triglycerides are made up of two main molecules,
glycerol and fatty acids.
But the triglycerides, tri means three.
Triglycerides have three fatty acids.
Now these fatty acids can either be saturated
or unsaturated.
In the case of saturated fatty acids, which is where
the term saturated fats comes from, saturated fatty acids,
a lot of times you'll see in solid form at room temperature.
They're a kind of fats.
Every chemical bond is filled up.
But in the unsaturated fatty acids, this is where your
unsaturated fats or unsaturated oils come from.
The unsaturated fatty acids do not have every chemical bond
filled up.
They potentially could form more bonds.
And these triglycerides are primarily gonna be
an energy stored molecule.
So if you have lipids stored in your body for long term
energy use, a lot of times they're stored as triglycerides.
So here's an example of how the triglycerides are formed,
and then two different types.
In Figure A on the left you're seeing, you have the three
yellow structures.
Those are your saturated fatty acids.
You can see every carbon has four bonds off it.
Every (mumbles).
It's just one over another.
And the top oval, the glycerol.
What ends up happening here is you can see how there is
an OH that is highlighted in blue.
And then another H on the glycerol.
Well if you take off the HOH, or H2O, by removing water,
that's dehydration synthesis.
You could make a new molecule.
Do that three times.
You bind three saturated fatty acids there, and now
you have a triglyceride with your B in the middle.
But if you end up having a triglyceride
which is unsaturated, that's C on the right-hand side.
You can notice how that as you go down those
fatty acid chains, sometimes there's a carbon carbon bond.
But instead of one line, meaning a single bond, there is
two lines, which causes the line to kind of angle out
a little bit.
That means you could technically add some more bonds
in there if you wanted to, some more hydrogen.
So we have our triglycerides.
Saturated, the middle is B.
Unsaturated fatty acids is the right, letter C.
The second main category of lipids is your phospholipid.
Now the phospholipid still has the same glycerol.
It still has fatty acids.
But now there's only two fatty acids.
The 3rd fatty acid has been switched as now
a phosphate group.
At the term phospholipid, you have a phosphate group.
Two fatty acids all attaching to glycerol.
Now what's unique is one end of this molecule
is water soluble, hydrophillic, water-loving.
But remember I said all lipids are insoluble.
That's still true because the other end of the molecule
is water insoluble, hydrophobic, water-fearing.
So even though a portion of this phospholipid could
be soluble in water, the other portion is still insoluble
in water.
So overall, that means the molecule cannot fully be soluble
in water.
So your phospholipid.
Their function, cell membrane.
They form the cell membrane of practically every cell
in your body.
Now it's not the only piece of a cell membrane but
the large component of the cell membrane.
So here is your phospholipid.
You can see the top sphere, which is referred to as
the polar head, is comprised of your glycerol molecule
and the phosphate group.
But coming off the other side are the two fatty acid chains.
Now these two fatty acid chains, one happens
to be saturated.
One happens to be unsaturated.
So which one's which?
As you're looking at the screen, is the left-hand one
the saturated or unsaturated?
The one on the left, which has the term fatty acid
pointing to it, that's the saturated fatty acid.
The one on the right-hand side of the screen, where you have
the bracket that says nonpolar, you can see there's
a double-bonded carbon in the middle there.
That means that's the unsaturated fatty acid.
And to round off the category of lipids, we have
our steroids.
Now all these steroids are composed of four carbon rings.
What makes these different from your carbohydrates
is these rings are actually sharing a side.
You can see other rings when you trace them.
They both have one side that is shared between each ring.
The carbohydrates do not share.
There's always a bond in between each monosaccharide,
or each ring.
So always as four carbon rings, and always as sharing sides.
The example you see here, cholesterol.
Now think of it as a whole, cholesterol's bad.
Not necessarily.
You have to have some cholesterol in your body
to function normally.
Now sure, if you have too much cholesterol, it could cause
a problem.
We have to have some there to help with
structural supports of your cell membrane and to help
with other normal cell functionality.
Your body naturally produces cholesterol.
The question is does it produce the right amount?
Or unfortunately, could it be producing too much?
This producing too much of this, then we've got a problem.
Estrogen, testosterone.
And what's even more interesting here is
the cholesterol molecule can head down and split
and be converted into estrogen and testosterone.
So cholesterol is actually kind of a starting material,
which helps produce the male sex hormone, testosterone,
and the female sex hormone, estrogen, your steroids.