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Specialty Chemistry Forums => Biochemistry and Chemical Biology Forum => Topic started by: OrionEmpire on March 11, 2016, 06:53:28 PM

Title: Phospholipid Bilayer, I think I finally understand it?
Post by: OrionEmpire on March 11, 2016, 06:53:28 PM

I was having trouble understanding the bilayer. I kept thinking wouldn't all phospholipids face the same direction, because of the water and what not? It made no sense to me. Then I remembered the cell pool, which has water in it. Thus the head of the outter layer of phospholipids stays by the water and the tail points inward. And then the phospholipids of the inner layer, don't face the same direction as the outter, because of the water from the cell pool, the head hangs by the cell pool and the tails in towards the center of the membrane? Is that correct? Thus the bilayer that forms automatically in water?

Title: Re: Phospholipid Bilayer, I think I finally understand it?
Post by: Arkcon on March 11, 2016, 07:20:14 PM

That's the way they're generally visualized, yes.

(https://upload.wikimedia.org/wikipedia/commons/f/f0/Lipid_bilayer_section.gif)

Title: Re: Phospholipid Bilayer, I think I finally understand it?
Post by: Arkcon on March 11, 2016, 07:22:59 PM

Note, in electron micrographs, we see two dense layers and a clear inner layer, that's due to the osmium staining.  The hydrocarbon chains are still in the middle.

Title: Re: Phospholipid Bilayer, I think I finally understand it?
Post by: OrionEmpire on March 11, 2016, 07:36:30 PM

So why don't they phospholipids form a single ring when put into water, instead of a bilayer? Sorry if that's an elementary question, I'm probably on the wrong forum. I'm having trouble finding an answer to that. None of my books or manuals seem to explain it, other than they just auto form the bilayer.

I was assuming it has something to do with when a cell splits, being the fact of a pre-existing cell pool. Again, I'm used to the how it works, pertaining to biology, not the why it works, pertaining to chemistry.

Title: Re: Phospholipid Bilayer, I think I finally understand it?
Post by: Burner on March 11, 2016, 08:47:20 PM

Phospholipids have a hydrophilic(water-loving) head and a hydrophobic(water-repelling) tail. So to minimize repulsion they tend to form bilayers so that the hydrophilic heads can face the water-based fluid(cytoplasm/tissue fluid/...) outside the bilayer.

Title: Re: Phospholipid Bilayer, I think I finally understand it?
Post by: Dan on March 12, 2016, 08:21:33 AM

Quote from: OrionEmpire on March 11, 2016, 07:36:30 PM

So why don't they phospholipids form a single ring when put into water, instead of a bilayer?

That can happen, but usually there is not enough space in the centre of the sphere for the hydrophobic groups.

Some discussion here: https://en.wikibooks.org/wiki/Structural_Biochemistry/Lipids/Micelles

Title: Re: Phospholipid Bilayer, I think I finally understand it?
Post by: Babcock_Hall on March 12, 2016, 11:48:08 AM

@OP, Would you explain what you mean by "cell pool?"

Title: Re: Phospholipid Bilayer, I think I finally understand it?
Post by: OrionEmpire on March 12, 2016, 09:25:22 PM

Quote from: Babcock_Hall on March 12, 2016, 11:48:08 AM

@OP, Would you explain what you mean by "cell pool?"

As in the aqueous, chemical liquid inside the cell, of which the other components lie in.

Title: Re: Phospholipid Bilayer, I think I finally understand it?
Post by: Babcock_Hall on March 14, 2016, 09:24:32 AM

Another name for this is cytoplasm.