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

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    For the phagocytosis question, I wrote about how the phagocyte engulfs the pathogen via endocytosis, this forms a phagosyme inside the cell, lysosomes fuse with the phagosyme, digesting enzymes are released into the vesicles containing the pathogen and they break down the pathogen into harmless substances. But people have out stuff about lymphocytes so maybe I've missed something or read the question wrong. :\
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    For stuff like the primary structure and enzyme answers for the respective questions if you put polypeptide (primary structure) and protein (enzyme) do you think I'd get those because they would just ignore the wrong answers instead of cancelling it out?

    Other than a few questions like the DNA evidence one and the potato one, I think largely that was a good paper... but I don't want to speak too soon!

    For the essay question on the pathogens were we supposed to write about phagocytosis or B and T cells? Because I thought the question asked what happened when the phagocyte had already become an APC so therefore phagocytosis has already happened right?
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    (Original post by krishkmistry)
    That was a question that deffo asked you to recall f211 knowledge


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    i just did f211 retake so i knew! its that they are push through gaps in cappilarrie walls! by hydrostatic pressure(optional)
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    (Original post by jackitsme)
    so do you think we got our anwsers right? :L
    yep I think so providing my 2 aren't under the same marking point
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    I Should really get off tsr! I've got chem tomorrow and this is really depressing LOL
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    (Original post by Deziah)
    For the phagocytosis question, I wrote about how the phagocyte engulfs the pathogen via endocytosis, this forms a phagosyme inside the cell, lysosomes fuse with the phagosyme, digesting enzymes are released into the vesicles containing the pathogen and they break down the pathogen into harmless substances. But people have out stuff about lymphocytes so maybe I've missed something or read the question wrong. :\
    I put this but also threw in a bit in the end about antigen presentation aiding the activation of the specific immune response as it aids clonal selection blah blah blah
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    for the amino acid structure . the second question . did u need to label the amine group and the carboxyl group or not
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    (Original post by lahabz2012)
    for the amino acid structure . the second question . did u need to label the amine group and the carboxyl group or not
    Oh god I hope not...it didn't say to...
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    What did people write for the question to do with ethanol and toxins?
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    anyone got access to the paper?
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    (Original post by g.k.galloway)
    yep I think so providing my 2 aren't under the same marking point
    ahh you did i hope i did tooo
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    What do u lot think the boundary will be? I think may be around 74 ish
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    (Original post by g.k.galloway)
    Oh god I hope not...it didn't say to...
    i didn't . but am not sure . if can just have a look at the qp, but unfortunately no1 managed to capture it yet
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    For the selective breeding one I put that;
    The farmer should choose the crop with resistance to the disease.
    He should then breed them asexually so that they are genetically identical and crop are resistant to the disease - which is ideal for the short term.
    He should also use another method of breeding to increase genetic diversity and variation, so if a new diseases arises in the future not all the crop will die.
    The breeded crop should pass their resistance to the disease onto their offspring, and he should carry this on for generations.
    Eventually all his crop will be resistant to the disease.
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    UNOFFICIAL MARK SCHEME ???? GRADE BOUNDARIES?? I thought it was terrible. Every body seems to think it was good, that must mean it was terrible. lol
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    Where did people draw bands on the centrifuge test tubes? :confused:
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    the very last question was NOT BECAUSE of micrscopess . it was because the water bear has evolved from a common ancestor by natural selection , mutation and u can mention also some environmental factors like competition and predators.....
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    How many marks was it for drawing hydrogen bonds? I totally misread the question and missed that out :'(


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    (Original post by Kayess67)
    For the 7 mark phagocyte question, it said describe how pathogens are destroyed AFTER the antigens are presented on the phagocyte cell surface. So surely this question was requiring you to talk about the cell-mediated response and T lymphocytes differentiating into T killer cells and secreting H2O2 into infected cells? I wrote about phagocytosis too just in case
    I am no examiner and I may be completely wrong but I think you've just completely misquoted what the question asked. It said explain how pathogens are destroyed after the pathogen binds with the receptor on the phagocyte.

    Nowhere was antigen stated. Antigens are presented AFTER the pathogen is destroyed.

    That said, you may well be right in saying that cytotoxic T cells secret hydrogen peroxide and possibly antibodies clumping pathogens together for phagocytosis.

    But I based my response on the phagocyte's mode of action, I think there is enough you can say there to get the six marks (plus the one mark for the correct sequencing).

    1. Pathogen is engulfed by folding of the membrane made possible by the phagocyte's extensive cytoskeleton - endocytosis/phagocytosis.
    2. Pathogen held in a vesicle named a phagosome.
    3. Lysosomes fuse with phagosome.
    4. Secrete digestive enzymes e.g lysins onto pathogen
    5. Pathogen is digested
    6. Antigen presented on plasma membrane
    7. Sequencing of marks 1-6

    Of course I may be wrong and I believe it may have been referring to cytotoxic cells and antibodies as well, but I think you can get at least the majority of the marks by describing phagocytosis correctly.
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    (Original post by Kayess67)
    Where did people draw bands on the centrifuge test tubes? :confused:
    We did this in class, but I didn't think it would come up. I put the first one in the middle, and the second one a thicker band where 14 was and a thinner band where 15 was
 
 
 
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