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    (Original post by imaam)
    Can anyone please summarise what phytokines do and all that Pr and Pfr stuff - its just too confusing... PLEASE
    Phytochromes are the photoreceptors in leaves, stem, root and shoot of plants.

    Pr is converted to Pfr in daylight, and Pfr is converted to Pr in night time.

    They control the flowering of plants (and germination of some). 'Long Day' plants will flower with a lot of Pfr as there is not much darkness so not much Pfr is converted back to Pr. 'Short Day' plants will flower with lots of Pr as there is enough darkness to convert the Pfr back to Pr.

    This means plants can flower in different seasons depending on the day length.

    There is also the fact that Pfr is changed back to Pr in far-red light, but that is unlikely to come up.
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    (Original post by Hibz93)
    In the article it says "viruses are recognized and destroyed by the immune system".
    How does that happen? In one of the notes here it says that blymphocytes produces antibodies that destroys it. But doesn't antibodies only destroy bacteria, or can it also destroy viruses?
    t killer cells causes the infected cell to lyse
    also the antibodies stop toxins reaching human cells
    and it binds to the capsid coat in clumps for the macrophages to easily recognise the clump and engulf it
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    hey guys.. how do we calculate heart rate from an ECG? i suck ath that!!! there is a que in specimen paper like that
    thnx in advance
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    Could someone please explain to me what we might need to know about stem cells?
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    (Original post by Hibz93)
    In the article it says "viruses are recognized and destroyed by the immune system".
    How does that happen? In one of the notes here it says that blymphocytes produces antibodies that destroys it. But doesn't antibodies only destroy bacteria, or can it also destroy viruses?
    B lymphocytes can recognise the viral antigens and become APCs themselves. The T-helper cells can then bind to the B cell APC and cause it to divide into B memory and B effector cells which differentiate into plasma cells which produce the antibodies. The anti-bodies can label the viruses which are still in the blood and allow the macrophages to engulf them. The viruses which have already infected the somatic cells can be destroyed by the T-killer cells.

    Someone correct me if I'm wrong though, my memory is a bit fuzzy.


    (Original post by Kayak)
    I'm too slow- get rather caught up in my game/book! And even when I do, by strange coincidence, a text will go off, so I will be accused of texting and not revising!
    Lol, practise makes perfect. I've done it so many times that it's turned into a reflex
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    i am sorry to ask guys, but does anyone have a link to the specimen paper and / or MS? i can't seem to find it anywhere!
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    (Original post by abuelzouz)
    hey guys.. how do we calculate heart rate from an ECG? i suck ath that!!! there is a que in specimen paper like that
    thnx in advance
    They should have time along the bottom. See how long it takes to get from one R wave to the next, that'll tell you how long each beat takes, then turn that into beats per minute.
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    (Original post by Meesta)
    i am sorry to ask guys, but does anyone have a link to the specimen paper and / or MS? i can't seem to find it anywhere!

    here u go ... all here

    http://www.edexcel.com/migrationdocu...ce-biology.pdf

    gd luck
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    oh god, im going to flop this for sure...... i know nothing....
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    (Original post by abuelzouz)
    here u go ... all here

    http://www.edexcel.com/migrationdocu...ce-biology.pdf

    gd luck
    ahhh thanks
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    (Original post by sheep_go_baa)
    You live in Kuwait?? So you're doing this syllabus from there?! wow
    yeaaah .. :P
    Cant see why that was shocking
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    (Original post by gildartz)
    They should have time along the bottom. See how long it takes to get from one R wave to the next, that'll tell you how long each beat takes, then turn that into beats per minute.
    thnx for replying bro..
    under graph it says 1 second.. (10 small blocks) and between each R wave there are 10 blocks also... 3 R waves... wts next?
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    Some people have suggested to do the last, 30 mark pre-release based question first.
    I don't even think that will have any benefit, is anyone here going to do that, and why?
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    List five distinctive effects of light on plant growth. (5)

    any ideas..? Not reli sure how to answer this

    Thanks, Charli
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    Wait, how come the June 2010 paper was 1h 30mins, but the Jan 2011 paper is 1h 45mins...are they not both out of 90???
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    (Original post by abuelzouz)
    thnx for replying bro..
    under graph it says 1 second.. (10 small blocks) and between each R wave there are 10 blocks also... 3 R waves... wts next?
    So 10 blocks correspond to 1 second? If so then the heart rate would be 60 bpm since each beat lasts for a second
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    (Original post by sheep_go_baa)
    Wait, how come the June 2010 paper was 1h 30mins, but the Jan 2011 paper is 1h 45mins...are they not both out of 90???
    In the examiner report it mentions that they found people struggled due to the time limitations, so they extended it. People couldn't finish all the pre-release questions apparently.
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    (Original post by Adam9)
    Some people have suggested to do the last, 30 mark pre-release based question first.
    I don't even think that will have any benefit, is anyone here going to do that, and why?
    prob to get the heart breaking questions out of the way!!! but i'm just going to do from 1-7.
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    (Original post by billybo_h)
    In the examiner report it mentions that they found people struggled due to the time limitations, so they extended it. People couldn't finish all the pre-release questions apparently.
    Oh phew! I thought there may have been some sneaky extra questions
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    exam is am righT?
 
 
 

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