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How does phospholipids aid the cell and the rest of the body

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How does phospholipids aid the cell and the rest of the body

Postby ccBiologist » Thu Sep 15, 2011 3:42 am

ok i know the structure of phospholipids but how does their structure aid the cell membrane or contribute to the cell membrane being semi-permeable ? I read that phospholipids anchor the cell membranes protein how does it do this? Also could anyone give some ways that the structure of phospholipids relates to its function in the cell membrane
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Postby ccBiologist » Thu Sep 15, 2011 3:51 am

also does phosolipids allow the cell to repair itself when torn
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Postby JackBean » Thu Sep 15, 2011 5:31 am

it's semi-permeable, because it has both hodrophobic (fatty acids) and hydrophilic (glycerol, phosphate and the rest), thus the molecule must be able to pass both parts to be able to pass through the membrane.
Further, there is the structure (the saturation) of the fatty acids and also the group attached to the phosphate, whichc differ on both sides of membrane.
http://www.biolib.cz/en/main/

Cis or trans? That's what matters.
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Postby ccBiologist » Thu Sep 15, 2011 5:38 am

thanks man im thinking in the right direction but another fuction of the phospholipid bi-layer is to anchor protein molecules to the cell membrane so they project outwards is there any simple explanation as to why the phospholipid bi-layer can anchor protein molecules together
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Postby Adz795 » Thu Sep 15, 2011 7:25 am

I suppose the integral proteins are simply suspended in the phospholipid bilayer. They are, in a way, floating there held by hydrophobic and hydrophilic interactions.
You see the region of the integral protein that is surrounded by the hydrophobic fatty acid 'tails' is itself hydrophobic. So the hydrophobic tails of phospholipids and hydrophobic regions of the protein are held together by hydrophobic interactions.
Now, the region of the protein that projects out of the bilayer either on the cytoplasmic or extracellular side is hydrophillic. Therefore, it stays there intact due to hydrophilic interactions with water and other substances(I presume).
So you see both parts of the protein, one inside the bilayer and one projecting outside on both sides, are held there like this.
Moreover, on the cytoplasmic side the integral and peripheral proteins are held or tied to the cytoskeleton. For example, integrins (the proteins that connect the cell to the extracellular matrix) are attached on the cytoplasmic side with actin filaments. I'm not quite sure if integrin-like binding to actin is prevalent for all the proteins embedded in the bilayer, but definitely there is some sort of tying on the cytoplasmic side.
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Postby Adz795 » Thu Sep 15, 2011 7:39 am

I speculate the following:

If the cell membrane is torn really badly then there would be an exchange of contents (of the cell and outside) to what extent depending on the gradients of various substances.
If there is a split in the membrane, the phospholipids should almost immediately patch up because the hydrophobic tails will be repelled by water and the split would be 'zipped' up.
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Postby JackBean » Thu Sep 15, 2011 10:28 am

Adz is right.
I would just add, that there can be proteins anchored by either fatty acid or some isoprenoid, which are hydrophobicand thus are hold in the membrane.
http://www.biolib.cz/en/main/

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Postby ccBiologist » Fri Sep 16, 2011 8:10 am

thanks guys much love
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