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OCR Biology F212 Revision [3rd June 2013] (Now Closed) Watch

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    Thank you so much guy


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    (Original post by amber206)
    Omg. I haven't even looked at this stuff yet.
    Not good D:
    i havent revised it either
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    wondering if anyone can help?
    I know that competitive inhibitors are a similar shape to the substrate molecule, and compete with the substrate for a place in the active site, blocking the substrate from binding to the active site, but are competitive inhibitors complementary shapes to the active site?
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    I'm revising the immune system at the moment.. and getting a little confused.

    So phagocytosis is like the first response, when a pathogen enters your body that it hasn't seen before? Also one of my revision guides is saying that antibodies bind to the antigens on the pathogen, then the receptors on the phagocytes bind to the antibodies that are already attached to the pathogens. Then the phagocyte engulfs the pathogen and you know the rest..

    I thought that antibodies were specific to antigens, so how would this happen if it was the first time a pathogen entered the body? I thought it took time to produce antibodies? And I thought antibodies were part of the immune response, not phagocytosis..

    All the revision guides are saying different things and now i'm just sat here very confused!! Exam is scaring me!!
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    (Original post by zoep23)
    wondering if anyone can help?
    I know that competitive inhibitors are a similar shape to the substrate molecule, and compete with the substrate for a place in the active site, blocking the substrate from binding to the active site, but are competitive inhibitors complementary shapes to the active site?
    No I think they are just 'similar shapes'.. they are complementary I suppose, because they fit, but they are not the perfect fit like the substrate to the active site.
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    Also wondering, is it just macrophages that present pathogens antigens on their surface after phagocytosis? Not neutrophils?
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    (Original post by KTucker93)
    Also wondering, is it just macrophages that present pathogens antigens on their surface after phagocytosis? Not neutrophils?
    Yes. They just use macrophages for OCR, although neutrophil may be correct, however just stick with macrophage for the purpose of the exam


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    Anyone have any predictions for what will come up on this exam?
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    (Original post by KTucker93)
    I'm revising the immune system at the moment.. and getting a little confused.

    So phagocytosis is like the first response, when a pathogen enters your body that it hasn't seen before? Also one of my revision guides is saying that antibodies bind to the antigens on the pathogen, then the receptors on the phagocytes bind to the antibodies that are already attached to the pathogens. Then the phagocyte engulfs the pathogen and you know the rest..

    I thought that antibodies were specific to antigens, so how would this happen if it was the first time a pathogen entered the body? I thought it took time to produce antibodies? And I thought antibodies were part of the immune response, not phagocytosis..

    All the revision guides are saying different things and now i'm just sat here very confused!! Exam is scaring me!!
    thanks for helping me! and what you've described seems like its come out of the purple ocr textbook. This book is great but sometimes its a bit iffy, I'd stick to what the mark scheme says on this one, that the phagocyte has a receptor on its cell surface membrane that recognises the antigen on a pathogen, and binds to the antigen then the process of phagocytosis follows..Antibodies have a constant region which allows them to bind to phagocytic cells and aid in the process of phagocytosis, I think this is what the textbook is using but just stick to the mark scheme and you can't go wrong
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    Revision notes attached for anyone who hasn't already seen/used them.

    Not mine btw.

    Hope the revision's going well everyone! I wish this module wasn't so wishy-washy in terms of content and mark schemes!
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  1. File Type: pdf F212 Revision.pdf (214.9 KB, 238 views)
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    In the specification it says 'describe the structure and mode of action of T lymphocytes and B lymphocytes..'

    None of my revision guides or the text book seem to have anything on the structure of them? None of them seem to go into too much detail about the different types of lymphocytes (memory, helper, killer etc).
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    Ok so tell me if this is wrong... pathogens enter the body, and the infected host cells release histamine. This attracts neutrophils to the area. Neutrophils phagocytose the pathogens. Histamine also causes a response that makes the capillaries leak more. This means more fluid leaves the capillaries into the lypmphatic system. Macrophages are in the lymph nodes. So macrophages phagocytose the pathogens that come into the lymph nodes, but they don't fully engulf the pathogen. They seperate the pathogens antigens and present them on their surface.


    Now this is where i'm getting confused.

    I then think that macrophages 'alert' the T cells, which differentiate into T killer cells, T helper cells and T memory cells (are they a non-specific T cell to start with? are they not already helper or killer or memory?). The T killer cells then attack infected host cells and kill them. T helper cells release cytokines to stimulate the B cells to divide. The B cells develop into plasma cells which produce antibodies. B cells also become memory cells which remain in the blood and are specific to that specific pathogen. They remain in the blood as immunological memory, so if that pathogen enters the body again, it will find it quickly and divide by mitosis.

    Please can someone tell me if thats all right??

    Also what is the difference between T memory and B memory cells?

    Sorry im asking so much but I need help! For some reason this is the module that is scaring me the most..
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    When writing an answer in an exam about water, can we you say 'oxygen has a δ- charge...' or do we have to say 'oxygen has a negative charge...' ??
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    (Original post by AGKhan)
    When writing an answer in an exam about water, can we you say 'oxygen has a δ- charge...' or do we have to say 'oxygen has a negative charge...' ??
    Well this is the thing, oxygen (in a water molecule) doesn't actually have a negative charge; as you have correctly identified it has a delta-negative charge, which is just a very small negative charge which is down to the polarity of the molecule.

    OCR would probably allow you to say "negative charge" but I would personaly go with the delta sign.
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    can anyone help? In the january 2011 paper there is a question "describe the ways in which the structure of collagen is similar to the structure of haemoglobin?"
    the mark scheme says:
    (collagen has)
    amino acid, chain / sequence ;
    peptide bonds ;
    helical / helix ;
    3 bonds / interactions from: disulfide / ionic / hydrogen /
    hydrophobic or hydrophilic ;
    quaternary structure ;
    more than one polypeptide / subunit ;

    Is it just me or does it not say in any textbook/revision guide that collagen also has a quaternary structure? Perhaps it has but i'd always been familiar with haemoglobin having one...
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    (Original post by zoep23)
    can anyone help? In the january 2011 paper there is a question "describe the ways in which the structure of collagen is similar to the structure of haemoglobin?"
    the mark scheme says:
    (collagen has)
    amino acid, chain / sequence ;
    peptide bonds ;
    helical / helix ;
    3 bonds / interactions from: disulfide / ionic / hydrogen /
    hydrophobic or hydrophilic ;
    quaternary structure ;
    more than one polypeptide / subunit ;

    Is it just me or does it not say in any textbook/revision guide that collagen also has a quaternary structure? Perhaps it has but i'd always been familiar with haemoglobin having one...
    Collagen does have a quartenary structure, however i can not find it in the OCR textbook, but i have found a website that does discuss this a liitle-it may be helpful! http://www.elmhurst.edu/~chm/vchembo...atprotein.html
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    Can someone please explain the difference between clonal selection and clonal expansion?
    Thanks
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    Also, with antibodies, do we need to know agglutination, lysis, antitoxins and opsonisation?
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    (Original post by amber206)
    Can someone please explain the difference between clonal selection and clonal expansion?
    Thanks
    Clonal selection is the selection of the correct lymphocyte with the complementary cell surface receptor to the antigen.
    Clonal expansion is when this selected lymphocyte divides many times by mitosis. Hope that helped! Also for antibodies all I've learnt is structure and function, agglutination and how that helps phagocytosis, and neutralisation.


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    (Original post by coco_madem0iselle)
    Clonal selection is the selection of the correct lymphocyte with the complementary cell surface receptor to the antigen.
    Clonal expansion is when this selected lymphocyte divides many times by mitosis. Hope that helped! Also for antibodies all I've learnt is structure and function, agglutination and how that helps phagocytosis, and neutralisation.


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    Thanks!
 
 
 
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