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    hey will give rep


    so i'm reading these notes I have and i understand whats going on apart from one bit. It first speaks about how we have the ATPase pump which actively transports sodium ions out and potassium in so we get a higher con of sodium outside the epithelium cells (i.e. in the lumen of the gut). Okay then we we have the sodium-glucose transporter protein to which we get glucose and sodium binding. So since the Atpase pump has created the high con gradient of sodium ions the sodium ions are gonna diffuse into the cell down their gradient. I've basically just summarised what I've learnt from the notes

    anyway then it goes on to say 'so while the sodium ions are diffusing DOWN their conc gradient, the glucose molecules can be carried up their con gradient. Now this is the bit I don't understand up the gradient means it will be carried from low to high concentration ..but if you look at the diagram in the lumen the glucose would be in a high concntration and in the blood it would be in a lower concentration so isn't it going from high to low ...I know its active transport of glucose so it's got to be going from low to high but looking at the diagram it doesn't seem as if this is what is occuring :confused:
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    (Original post by CasualSoul)
    hey will give rep


    so i'm reading these notes I have and i understand whats going on apart from one bit. It first speaks about how we have the ATPase pump which actively transports sodium ions out and potassium in so we get a higher con of sodium outside the epithelium cells (i.e. in the lumen of the gut). Okay then we we have the sodium-glucose transporter protein to which we get glucose and sodium binding. So since the Atpase pump has created the high con gradient of sodium ions the sodium ions are gonna diffuse into the cell down their gradient. I've basically just summarised what I've learnt from the notes

    anyway then it goes on to say 'so while the sodium ions are diffusing DOWN their conc gradient, the glucose molecules can be carried up their con gradient. Now this is the bit I don't understand up the gradient means it will be carried from low to high concentration ..but if you look at the diagram in the lumen the glucose would be in a high concntration and in the blood it would be in a lower concentration so isn't it going from high to low ...I know its active transport of glucose so it's got to be going from low to high but looking at the diagram it doesn't seem as if this is what is occuring :confused:
    For a start, don't forget that there's glucose in the cell as well-I just did a cheeky google, and whilst I can't find a figure to put on [intracellular glucose], I did see that glucose moves from cell to blood via GLUT2 transporters (which mediate facilitated diffusion)-this shows glucose concentration is higher in the cell than the bloodstream.

    That aside, let's remember that the luminal glucose concentration will fall gradually as more and more glucose is absorbed. Even if luminal glucose starts off higher than intracellular glucose, eventually you'll reach a point where enough has been absorbed from the lumen that glucose concentration is equal across the cell membrane; to keep absorbing past this point, you need some sort of active process.
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    (Original post by schtim)
    For a start, don't forget that there's glucose in the cell as well-I just did a cheeky google, and whilst I can't find a figure to put on [intracellular glucose], I did see that glucose moves from cell to blood via GLUT2 transporters (which mediate facilitated diffusion)-this shows glucose concentration is higher in the cell than the bloodstream.

    That aside, let's remember that the luminal glucose concentration will fall gradually as more and more glucose is absorbed. Even if luminal glucose starts off higher than intracellular glucose, eventually you'll reach a point where enough has been absorbed from the lumen that glucose concentration is equal across the cell membrane; to keep absorbing past this point, you need some sort of active process.
    thanks, run out of rep today. Promise to give tomorrow
 
 
 
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