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Thread: Facilitated diffusion, active diffusion & simple diffusi

  1. #1 Facilitated diffusion, active diffusion & simple diffusi 
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    Hi help I'm stuck! I need to write an essay that talks about the different types of diffusion across a cell membrane. Specifically I need to compare a neurone cell, with either a blood cell, or a epithelial cell. My tutor has given some strong hints that she would prefer a comparison of a neurone with a blood cell though. (I'm not sure if she means red or white however?) as both of these apparently show the full range of difference membrane transport methods. I seem to be doing OK with Neurones as there appears to be plenty of information out there, however I'm having a terrible time sourcing any information on the full range/function of membrane transport in blood cells.

    Can anyone please point me to some sources where I might be able to find out something about this?

    Thanks!


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  3. #2  
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    Concerning iron transport into red blood cells:

    From:

    http://courses.washington.edu/conj/bess/iron/iron.htm

    Iron is brought into the cell through an active transport process involving the protein DMT-1 (divalent metal transporter-1), which is expressed on the apical surface of enterocytes in the initial part of the duodenum. DMT-1 is not specific to iron, and can transport other metal ions such as zinc, copper, cobalt, manganese, cadmium or lead.

    Once inside the enterocyte, there are two fates for iron:


    It may leave the enterocyte and enter the body via the basolateral transporter known as ferroportin.

    It can be bound to ferritin, an intracellular iron-binding protein. For the most part, iron bound to ferritin in the enterocyte will remain there. This iron will be lost from the body when the enterocyte dies and is sloughed off from the tip of the villus.
    Iron that enters the body from the basolateral surface of the enterocyte is rapidly bound to transferrin, an iron-binding protein of the blood. Transferrin delivers iron to red blood cell precursors, that take up iron bound to transferrin via receptor-mediated endocytosis.

    Normally, the capacity of transferrin to bind iron in the plasma greatly exceeds the amount of circulating iron. The transferrin saturation (percent of transferrin occupied by iron) is measured to determine if an individual has an excessive load of iron in the body. The normal transferrin saturation is in the range of 20-50%.


    --------------------------------------------------------------------------------

    Iron absorption by the enterocyte is programmed to match the body's needs. There are two major signals that affect iron absorption.

    1. One signal reflects the need for iron due to hematopoiesis (red blood cell generation). The hormone erythropoietin (produced by the kidneys) stimulates red blood cell production, but it is NOT the signal that stimulates iron absorption. Rather, once hematopoiesis is stimulated, another signal is generated that stimulates iron absorption.

    2. A second signal depends upon the amount of iron in body stores. Iron absorption is stimulated if the level in body stores is low.

    These signals (and others) regulate iron absorption in the proximal duodenum, where iron is absorbed. An important player in this regulation is the recently discovered hormone hepcidin. Hepcidin is produced by hepatocytes when iron stores are full. Inflammation can also stimulate hepcidin production.


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  4. #3  
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    Thanks, that's great!!! But I specifically need something that talks about the different kinds of membrane transport for each specific cell type. I think I need to cover all (or at least the majority) of different membrane transport types. The advantage (or so my tutor has led me to believe) of using blood cells and neurons is that these cover the full range of transport types and may (although I'm not clear about this yet!) in some cases even use membrane transport mechanisms that are different from each other. (Or that are specific to that cell type only).

    Ideally I do need a resource that talks about membrane transport, giving more than the one example above (which is still great BTW)

    This is a kind of "contrast and compare" type exercise, as in contrast and compare the membrane transport mechanisms of one type of cell with the membrane transport mechanisms of another type of cell.

    Any help would be greatly appreciated.
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