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    Please help with this question
    Explain why diffusion is described as the net movement of molecules or ions.
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    One more question...
    Describe how epithelial cells of the villi absorb molecules of glucose from the gut contents.
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    For the first one: diffusion depends on molecules moving freely in a medium to achieve a uniform concentration. It's the net movement because if you imagine molecules crossing a membrane for example they can move in or out, it's just that they will be moving more towards the side with the lowest concentration.

    The epithelial cells have glucose transporters to take up glucose.
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    (Original post by alkyone)
    For the first one: diffusion depends on molecules moving freely in a medium to achieve a uniform concentration. It's the net movement because if you imagine molecules crossing a membrane for example they can move in or out, it's just that they will be moving more towards the side with the lowest concentration.

    The epithelial cells have glucose transporters to take up glucose.
    Thank you
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    (Original post by Petch_su)
    Please help with this question
    Explain why diffusion is described as the net movement of molecules or ions.
    Thank you
    This is because diffusion occurs when there is a concentration gradient between two regions. It continuous until the same concentration is reached for both regions. While the particles are still moving about ( after the concentration is the same at both regions), the concentration will remain the same as there is no net movement. At this point it is no longer called diffusion!
 
 
 
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