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    hi im learning the kideny at the moment and am finding it hard memorising it all. does anyone know any good revision sites? and also can anyone explain selective reabsorption?
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    WAGUM = water, amino acids, glucose, urea, mineral ions are reabsorbed in the prox. conv. tubule... only way I remembered it
    actually about those amino acids..... small proteins are absorbed by the walls of the prox conv tubule, digested, then the amino acids make their merry way into the blood


    http://www.biologymad.com/Kidneys/Kidneys.htm

    Have fun :-)
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    i think(but i may be wrong) that selective reabsorption occurs because only molecules that need to be reabsorbed ie glucose have enough protein carrier molecules, or protein channels in the membrane of the proximal convoluted tubule or membrane? is that right? i find the kidney hard as well, i learnt it by writing out flow charts of what happens
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    thanks guys uve really helped the link looks good. i dont understand why urea is reabsorbed. rep is waiting to be given out!
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    Urea is reabsorbed because it's a small, soluble molecule which can diffuse passively down it's concentration gradient, through the cells of the wall of the convoluted tubule.
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    I do edexcel, but in an past paper question on reabsorption in the PCT, it said Urea was NOT absorbed.
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    The textbook written by the OCR examiners disagrees.
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    (Original post by oneeyedandgreen)
    i think(but i may be wrong) that selective reabsorption occurs because only molecules that need to be reabsorbed ie glucose have enough protein carrier molecules, or protein channels in the membrane of the proximal convoluted tubule or membrane? is that right? i find the kidney hard as well, i learnt it by writing out flow charts of what happens
    Yeah, is right

    Just remember that the by glucose and amino acids being actively transported via carrier proteins in the proximal convoluted tubule, makes the water potential of the blood to become more negative.

    This causes water to move out of the proximal convoluted tubule down a water conc gradient (since it is now less negative in the proximal convoluted tubule), which causes water to move out by osmosis.

    Also the reason the reason why urea concentration increases in the proximal convoluted tubule is because water moves out the proximal convoluted tubule by osmosis... Remember that urea is not reabsorbed in the blood (for Edexcel exams you don't need to know what really happens in the kidney)

    Just keep things simple and you'll be fine.
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    This is for OCR. The OCR textbook makes clear that some urea is reabsorbed.
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    yeah its really strange about the urea thing but apparently ocr say that it is reabsorbed because its small and soluble they also say that some urea is present in your sweat.
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    All the urea is excreted eventually.
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    so does it just go around until it secreted (eventually) then?
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    essential a2 bio for ocr says(this is in my own, basic phrasing) that it is readsorbed when theres low water levels in the blood. ADH leads to the distal conv. tubuel and collecting duct becoming more permeable to urea, this lowers the water potential in the interstitial region thus, more water diffuses into this space via osmosis
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    eventually all the urea is removed but by then you've made more so you're probably going to always have a small amount of urea in the blood
 
 
 
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