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  1. #1
    Correct my English!
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    Default A Biology question

    Greetings. I am in urgent need on clarification of a Biology question. In the cell membrane, how does the water molecule goes through the bilayer of phospholipid WITHOUT entering the protein pores? Since the hydrophobic end of the phospholipid creates a barrier in the middle of cell membrane, why is it able to go through, then?

    Thanks

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  2. #2
    Y'arrr
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    Default Re: A Biology question

    Osmosis.

    Water molecules are small enough to pass through the pores in the plasma membrane and will do so in either direction quite freely. The net movement of water across a membrane is called osmosis.

    Osmosis, is the passive diffusion of water molecules through a semi-permeable membrane from a dilute solution to a more concentrated solution.
    Last edited by ninja; 19-04-2005 at 09:07 AM.
    There are no such things as ghosts, only clumsy ninjas.

  3. #3
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    Default Re: A Biology question

    Ninja, you mentioned that the water will be able to go into the the pores of the plasma membrane, I have no problem with that. How about the center part? Water is a polar molecule, while the tail end of the phospholipid is non-polar. Polar and non-polar doesn't mix together, so how did the water molecule manage to pass through?

    Cheers

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  4. #4
    Y'arrr
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    Default Re: A Biology question

    I knew this degree would come in handy at some stag or other.

    Pores wasn't quite the right analogy, getting ones head to work at such small scales can be tough.

    By pores, I'm referring to aquaporins, which are proteins that sit in the cell membrane and operate as water channels.

    A bit more info:
    http://en.wikipedia.org/wiki/Aquaporin

    A lot more info (with a 13mb movie):
    http://www.ks.uiuc.edu/Research/aquaporins/
    There are no such things as ghosts, only clumsy ninjas.

  5. #5
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    Default Re: A Biology question

    Ahh. Osmosis. Now my school biology days come flooding back to me.

    Only 10 years ago, but the memory of dissecting locusts and rats intestines, and counting drosophila is all too fresh in the memory.

  6. #6
    Lets play Metla's Avatar
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    Default Re: A Biology question

    Quote Originally Posted by ninja
    I knew this degree would come in handy at some stag or other.

    Pores wasn't quite the right analogy, getting ones head to work at such small scales can be tough.

    By pores, I'm referring to aquaporins, which are proteins that sit in the cell membrane and operate as water channels.

    A bit more info:
    http://en.wikipedia.org/wiki/Aquaporin

    A lot more info (with a 13mb movie):
    http://www.ks.uiuc.edu/Research/aquaporins/


    At which time I would like to point out the spelling mistake in the first line, this of course means that any information you have shared now becomes irrelevant and is dismissed as not worthy.

    And if anyone makes a further post that contains no spelling mistakes it will immediately be of more worth then yours, even if the offered advice is complete crap.

    This may seem harsh, even anal but we must have standards, it makes some people feel superior.
    better Dredd then dead

  7. #7
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    Default Re: A Biology question

    Quote Originally Posted by jameskan
    In the cell membrane, how does the water molecule goes through the bilayer of phospholipid WITHOUT entering the protein pores? Since the hydrophobic end of the phospholipid creates a barrier in the middle of cell membrane, why is it able to go through, then?
    To put it simply, it doesn't. It has to go via the specialised protein pores.

    Hope you credit PF1 with your homework assignments.

  8. #8
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    Default Re: A Biology question

    Quote Originally Posted by Metla
    At which time I would like to point out the spelling mistake in the first line, this of course means that any information you have shared now becomes irrelevant and is dismissed as not worthy.

    And if anyone makes a further post that contains no spelling mistakes it will immediately be of more worth then yours, even if the offered advice is complete crap.

    This may seem harsh, even anal but we must have standards, it makes some people feel superior.
    There is a big difference between a typing mistake and the bad spelling and grammar that is all too often evident here.
    This does not apply to you though Metla, I find your posts of high quality and I just hope that it does not make you feel superior as you suggest it could do.

  9. #9
    Correct my English!
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    Default Re: A Biology question

    Quote Originally Posted by Jen
    To put it simply, it doesn't. It has to go via the specialised protein pores.
    Well, I just found out this information from a friend of mine. The water molecules have alternative way of going in / out of the cell besides through the specialized protein. He said that the water molecule is able to go through between the two tails of the phospholipid , which explains why it is able to do so without the assistance of a protein. I am not too sure on his statement, so perhaps someone is able to pinpoint me to a link for more info on that?

    Quote Originally Posted by Jen
    Hope you credit PF1 with your homework assignments.
    Actually, my Biology teacher and I had an "argument" on this issue. He claimed that water molecules are not able to go in /out of the cell without the need of a protein molecule, while I was saying that it is able to do so. Yeah, sure Jen, I will say that I've got my sources from my "agents"

    Cheers and thanks for the great replies, everyone

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  10. #10
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    Default Re: A Biology question

    Oooh isn't it so nice to see some mutual back scratching and every one getting along so nicely. Just makes your heart swell up to the brim with pride

    PS. Where's the little love emoticons when you desperately need em? Bah! I tell you, the world is going to the dogs, again

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