Carrier and Channel Proteins

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vertciel
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Carrier and Channel Proteins

Post by vertciel » Sat Sep 22, 2007 6:54 pm

Hello everyone,

First post here, and this looks like a great place to be!

I take Grade 11 Biology. My textbook says that carrier proteins can bring only non-charged substances through the cell membrane, while channel proteins can bring charged substances through the membrane. Unfortunately, it does not explain these two characteristics.

So my question is: why can't carrier proteins bring charged substances across the cell membrane?

Thanks.

daniel.kurz
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Post by daniel.kurz » Sun Sep 23, 2007 3:16 am

Best easy explanation that I can give without getting too detailed is that in channel proteins they have polarity that allows them to be embedded in the cell membrane. This polarity allows molecules that are also polar to slip in. In the case of carrier proteins they bond to nonpolar molecules and have to use active transport of some kind to pull the molecule through the membrane. Look this up online and you should find some stuff.

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mith
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Post by mith » Sun Sep 23, 2007 2:27 pm

Except carrier proteins can also do it without atp...
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MrMistery
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Post by MrMistery » Mon Sep 24, 2007 10:06 am

carrier protein mechanism:
1.bind to the substance on one side of the membrane
2. diffuse to the other side of the membrane
3. release the substance to the other side

The speed of this depends on a number of factors: the dissociation constant of the protein, the size of the protein+ligand, the fluidity of the membrane etc
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