Polar molecules entering cells

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REN
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Polar molecules entering cells

Post by REN » Mon Mar 06, 2006 2:26 pm

I have two questions I can't seem to find the answer to. The questions
state:(1) Most polar molecules and ions cannot enter cells. Why? (2) Many food particles are polar. How do these get into a cell?
I have searched my text book and the web(my mom have tried to help also but discussing it with her makes it that more confusing). At first I thought maybe the polar molecules held a charge(Positive or negitive) and because the phosolipid-bilayer surrounding the cell was also polar that maybe they repelled each other. Then I thought that maybe for the food molecules to enter the cell they used active transport. I have looked at many diagrams of the phosolipid-bilayer and active transport, but the more and more I look at them, the less and less I believe that it has anything to do with polar molecules entering a cell at all.
Please anyone that can help my understanding will be truley appreciated. Thank you
Ren

rmh2005
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Post by rmh2005 » Mon Mar 06, 2006 3:35 pm

I had that same question, and I got my answer from another forum in here.
1) They cannot diffuse through the membrane because the membrane is nonpolar. They are repelled away from the membrane.
2) They do it through transport proteins.
I am pretty sure that is what they were. I hope that helped

bearhug
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Post by bearhug » Mon Mar 06, 2006 3:38 pm

The phospholipid bilayer is both hydrophobic and hydrophilic. Polar molecules have a hard time entering the cell is because it is hydrophilic and can't interact with the hydrphobic tails inside the membrane. In order to go through it uses facilitated diffusion.
"In omnias paratus!"

REN
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Post by REN » Mon Mar 06, 2006 3:39 pm

Very much so. Thank you
Ren

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