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    cells with Hb^s.
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    i think its coz the plasmodium divides in the red blood cells rapidly and so the rb cells burst into the blood stream, causing bouts of fever.
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    (Original post by sparkleyez)
    i think its coz the plasmodium divides in the red blood cells rapidly and so the rb cells burst into the blood stream, causing bouts of fever.
    so plasmodium cannot exsist in cresent shaped RBCs and so they dont burst, im confused.
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    (Original post by w8wizz)
    cells with Hb^s.
    Yeah, this is why carriers of sickel cell anaemia (having one 'normal' allele and one sickel allele fo haemoglobin) have resistance to malaria. Not really sure why the plasmodium cannot exist in sickel red cells...
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    Red cells from people with sickle trait do not sickle to any significant degree at normal venous oxygen tension. Very low oxygen tensions will cause the cells to sickle, however. For example, extreme exercise at high altitude increases the number of sickled erythrocytes in venous blood samples from people with sickle cell trait (Martin, et al., 1989). Sickle trait red cells infected with the P. falciparum parasite deform, presumably because the parasite reduces the oxygen tension within the erythrocytes to very low levels as it carries out its metabolism. Deformation of sickle trait erythrocytes would mark these cells as abnormal and target them for destruction by phagocytes( Luzzatto, et al., 1970)
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    The reason that plasmodium cannot exist in sickel red blood cells is simply because the sickel red blood cells have a much reduced life span that prevents the plasmodium being able to reproduce in red blood cells.
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    (Original post by Revenged)
    The reason that plasmodium cannot exist in sickel red blood cells is simply because the sickel red blood cells have a much reduced life span that prevents the plasmodium being able to reproduce in red blood cells.
    Yes, but people with sickle cell trait will normally have erythrocytes with normal morphology.

    /edit: plus, if i remember correctly the life cycle of the p.falciparum is very short, something like a couple of days, so would be able to reproduce easily in an erythrocyte with even a considerably shortened lifespan.
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    (Original post by j00ni)
    Yes, but people with sickle cell trait will normally have erythrocytes with normal morphology.

    /edit: plus, if i remember correctly the life cycle of the p.falciparum is very short, something like a couple of days, so would be able to reproduce easily in an erythrocyte with even a considerably shortened lifespan.
    Well... I see what you mean, perhaps lecturer was wrong... but i googled and this is what i got:

    'The precise mechanism by which sickle cell trait imparts resistance to malaria is unknown'

    http://www.google.co.uk/search?hl=en...esistance&meta=

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    I think if you're heterozygous for the gene then your RBCs will only crumple into the sickle shape at low partial pressures of oxygen. But when an RBC is infected by plasmodium you get a low partial pressur eof oxygen because of the parasite's respiration, so the red blood cell collapses into the sickle shape and gets disposed of. I think.

    edit: yep http://www.thestudentroom.co.uk/showthread.php?t=183131
 
 
 

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