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    Hey everyone,

    I'm using the AQA Spec A Further Studies in Human Biology book by Baker, Indge and Rowland and am getting confused about the absorption bit in chapter 9 (p.191)

    It says that amino acids are absorbed into the epithelial cells of the small intestine by facilitated diffusion. But the diagram shows the absorption occurring by active transport! So I don't know which one is right. I'm thinking that the right answer is active transport and that the text is wrong but I'm not sure. Anyone know? Am I just reading the whole thing totally wrong?

    The thing is that it also says that there is a slight difference in the absorption of amino acids and glucose. What would the difference be if amino acids are absorbed by active transport because then it is the same? I think the difference has something to do with the use of sodium ions but again I don't know. Any ideas?

    I hope that makes sense to you all, any help would be really appreciated.

    Thanx
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    Overall, it's a type of active transport- ATP is used in pumping sodium ions out of the cells into the lumen of the small intenstines, creating a higher concentration of sodium ions in the lumen than in the cells. This means sodium can freely diffuse back down its concentration gradient, from the lumen across the membrane carrying with it amino acids as a cotransport mechanism (and this bit would be 'facilitated diffusion').
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    Thanks for answering endeavour, I wasn't sure anyone would bother cos the post was so long - so active transport into the small intestine cells from the lumen...and facilitated diffusion from the small intestine cells into the capillaries?

    The text in the book is wrong, right?
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    active transport apparently, my teacher picked up on the same thing n sed it was wrong in the small book but correct in the large main book. Ridiculous seein as its written by the same bloke
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    (Original post by wednesburywench)
    active transport apparently, my teacher picked up on the same thing n sed it was wrong in the small book but correct in the large main book. Ridiculous seein as its written by the same bloke
    Thats brilliant thanks. Just as long as I know I'm revising the right thing.
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    active transport uses carrier proteins in the membrane and ATP energy to move thigs against the conc gradient... right?

    does faciliated diffusion also carrier proteins as well... what stops these productions from simply diffusing back out again?

    and do these carrier proteins change shape when the substrate lands on the causing the substrate to be brought into the cell...

    soz, it was ages ago i did unit 1
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    nah facilitated diffusion uses protein channels
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    what exactly is the difference?
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    (Original post by animaluvva)
    Thanks for answering endeavour, I wasn't sure anyone would bother cos the post was so long - so active transport into the small intestine cells from the lumen...and facilitated diffusion from the small intestine cells into the capillaries?

    The text in the book is wrong, right?
    i got confused wiv the same thing.
    so is it active transport into the epithelial cells from the lumen for amino acid and glucose. im confused cos the book says that glucose and amino acid are different.
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    (Original post by ky1986)
    i got confused wiv the same thing.
    so is it active transport into the epithelial cells from the lumen for amino acid and glucose. im confused cos the book says that glucose and amino acid are different.
    Hey, from the answers I got on here and from what I have read I'd say yeah, active transport into the cell from the lumen and facilitated diffusion out the other side into the capillaries.

    I'm still confused about the book saying that they're different because I don't know what the difference between glucose absorption and amino acid absorption could be. If anyone knows that'd be great?
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    I thought glucose and amino acids were absorbed in the same way too...
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    The mechanism you're talking about is normally referred to as a type of active transport as it does use energy from ATP hydrolysis to drive in amino acids to the cells against their concentration gradient.
    The thing is, the mechanism relies of the facillitated diffusion of Na+ ions down their concentration gradient (which was set up by active transport) through a channel (cotransport) protein.

    So in other words - it is active transport of amino acids using facillitated diffusion of Na+ ions.
    There are several methods of glucose transport, but as far as I know - the one that happens in the human digestive system is the same as the above mechanism but relies of different channel proteins (as they are specific to the substrate).
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    (Original post by oxymoron)
    The mechanism you're talking about is normally referred to as a type of active transport as it does use energy from ATP hydrolysis to drive in amino acids to the cells against their concentration gradient.
    The thing is, the mechanism relies of the facillitated diffusion of Na+ ions down their concentration gradient (which was set up by active transport) through a channel (cotransport) protein.

    So in other words - it is active transport of amino acids using facillitated diffusion of Na+ ions.
    There are several methods of glucose transport, but as far as I know - the one that happens in the human digestive system is the same as the above mechanism but relies of different channel proteins (as they are specific to the substrate).
    ohhhhhh thanks, so much clearer
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    every1 who is confused try this link.....
    but its still different from the AQA A textbook tho

    http://www.biologymad.com/Digestion/...iles/frame.htm
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    (Original post by animaluvva)
    Hey, from the answers I got on here and from what I have read I'd say yeah, active transport into the cell from the lumen and facilitated diffusion out the other side into the capillaries.

    I'm still confused about the book saying that they're different because I don't know what the difference between glucose absorption and amino acid absorption could be. If anyone knows that'd be great?
    hey in the June 04 paper page 10, it shows the absorption of amino acid, which is same as described in the text book. check it out

    http://www.aqa.org.uk/qual/gceasa/qp...W-QP-Jun04.pdf
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    (Original post by ky1986)
    hey in the June 04 paper page 10, it shows the absorption of amino acid, which is same as described in the text book. check it out

    http://www.aqa.org.uk/qual/gceasa/qp...W-QP-Jun04.pdf
    Oh man, you're right - this stresses me out soooo much :mad: If they just wrote the book right in the first place for God sake, I mean something's wrong, the text in the book or the diagram but what are supposed to do, guess?

    I suppose we're gonna have to go with facilitated diffusion then and look at it in the way that oxymoron posted that its facilitated diffusion of sodium ions rather than the amino acids. I'm still kinda confused and getting more and more p**sed off with this book by the minute!
 
 
 
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