Wednesday, July 22, 2009

Cell integrity and why vitamin E does not have a carrier protein

Carrying on from yesterday's post vitamin E, unlike the other fat soluble vitamins, does not need a carry protein. Your body is mostly water and as we know water and fat doesn't mix well. So the carrier proteins are need to carry the fat soluble vitamins around the body. The simplest way to imagine this is that the carrier proteins are like a small parcel. The inside of the parcel has fat loving proteins which attract the fat soluble vitamin. The outside of the parcel is water loving proteins allowing it to travel in the body.

Why doesn't vitamin E need these carrier proteins? And why does the paper state
The majority of the functionality of vitamin E is through its role as an antioxidant, maintaining the structural integrity of virtually all cells n the body.
It is the "structural integrity" bit that I find new. We all know that Vitamin E is an antioxidant but I didn't realize it was about maintaining structural integrity.

However both bits of information, (1) Vitamin E doesn't need carrier protein and (2) maintains structural integrity, seem to be related. Have a look at the following picture of vitamin E (picture credit) . On the left hand side you can see some O's which indicate oxygen and these are water loving. The long tall on the right side is a a fatty acid (eg bit of fat).

Now lets look at a cell membrane component shown below. Again on the left hand side we see some O's and also a hexagonal structure (it is a different way of drawing it than above). On the right hand side is two fatty chains. These molecules call phospholipids and pack in to make cellular walls/membranes (picture credit)

So a cell membrane has lots of these phospholipids joined together (see diagram below) One set of phospholipds are facing out of the cell, and the other facing inside the wall. This is shown in the picture below. The red balls are the water loving bits (bits to left above), and the yellow tails are the fatty tails. So you can see that vitamin E would fit really nicely into a bilipid membrane. This is because Vitamin E has a more water soluble head, and a fatty tale. Thus they do not need a carrier protein as it can "pop"into any cell in the body with ease. And this explains why they are needed for cell integrity. Because they will be the major antioxidant in the cell wall. And without this antioxidant the cell would self destruct so to speak. (picture credit)

The only question I have now is how does vitamin E find it's way into every cell in the body? Presumably vitamin E can be easily absorbed by the stomach cells, and passed onto blood cells. But how is it unloaded from the blood cells into other cells?

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