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PROFESSOR CIMA: OK, the other modification that's really important
and you hear about all the time are lipoproteins. So lipo, you know, oil, fat--
so what is a lipoprotein? Whoops, I remember it was out of order.
Lipoproteins look like this. They are proteins conjugated with these lipids.
Remember, lipids make up the cell wall. Well, they look kind of like a mini cell.
And in fact, what they do is they transport things like,
well, lipids, fats-- lipids are fats--
and other cholesterol around your body. And embedded in their surface and conjugated
to these lipids is a protein that helps target this thing to where
it's supposed to go. So for example, in LDL here--
low density lipoprotein-- and they categorize that by the density of
these particles. It has a protein on the surface that targets
this payload to actually deposit on certain cells to be engulfed by
certain cells. So its job is to transport this payload of
fat to cells that present what's called a receptor.
It's a matching protein for the protein on the
surface of the LDL particle. And then it gets engulfed.
So that's called apoprotein B. And it binds to these receptors on certain
cells that then engulf this fat and use it. If you have too much of this, it is transporting
to these cells that don't need it.
HDL, on the other hand, high density lipoprotein, is the same thing.
It's got a protein on its surface. But what it does, it's got a binding site
on it for a receptor in the liver to metabolize this stuff, to get rid of it.
So now you know why they talk about this LDL, HDL balance.
When you get my age, you get to start worrying about that HDL, LDL balance.
You want the good HDL, the good lipids, and you don't want the bad
ones, the low density lipoproteins. OK, so those are important modifications.