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    (Original post by hellosarah)
    hahhaha, i am never ready!! I'm retaking it, if i get an E again, i may just have a mental crisis. Are you ready?
    I don't think you can ever be ready for a test but this one I am seriously not ready for!
    Just had a panic attack feeling I don't know anything!
    I blame my maths exam - I was concentrating on that
    but yh, hope i do well. Good luck! and judging from your posts, I really don't think you'll get an E - you'll do a lot better
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    (Original post by giraffegiraffe)
    - measure size of image given (mm)
    - multiply by 1000 (convert to micrometers)
    - divide by the magnification (given or work it out- see below)
    = actual size (in micrometers)

    If you don't know the magnification and can't work it out from
    magnification = size of image over actual size,

    then work out magnification from the scale line:

    magnification = length of scale line given divided by length of scale line measured (mm)

    hope that helped
    thanks it really did
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    (Original post by hellosarah)
    hahhaha, i am never ready!! I'm retaking it, if i get an E again, i may just have a mental crisis. Are you ready?
    At least your situation is slightly better than mine. If I get a U again then I will have a massive mental crisis and hell knows what will happen. I STILL haven't worked out how I did so bad, I did loads of revision for it the first time and loads for this retake.
    Good luck anyway!
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    livingforthefuture- glad to hear it hope i remember it for tomorrow

    (Original post by pastpaper-guy)
    possible how science works questions?
    potometer setting up/precautions seems to come up a lot, no air bubbles, dry leaves, airtight seal etc!
    do we have to know any other practical stuff?
    oh- spirometer precautions- disinfect the mouthpiece and use soda lime to absorb CO2
    anything else?
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    (Original post by giraffegiraffe)
    livingforthefuture- glad to hear it hope i remember it for tomorrow


    potometer setting up/precautions seems to come up a lot, no air bubbles, dry leaves, airtight seal etc!
    do we have to know any other practical stuff?
    oh- spirometer precautions- disinfect the mouthpiece and use soda lime to absorb CO2
    anything else?
    im just worried they will try to incorporate some of the syllabus into a real example. E.g they give you a question about the heart and talk about a kid who has a condition where the right atria has a hole in it.
    Explain why the kid feels tired alot of the time?


    not exactly like that but u get the point
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    Can anyone willing to help follow this link:
    http://www.thestudentroom.co.uk/show...ghlight=phloem.
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    (Original post by pastpaper-guy)
    im just worried they will try to incorporate some of the syllabus into a real example. E.g they give you a question about the heart and talk about a kid who has a condition where the right atria has a hole in it.
    Explain why the kid feels tired alot of the time?


    not exactly like that but u get the point
    ohhh yeah i see what you mean but gosh i hope not .. the not-straightforward questions are the worst! its so hard to try to realise what they want you to say. the pastpaper questions i've tried so far have been kindof straightforward in the way they're asked but its just getting those exact words in which is a killer!
    is everyone using the black and purple ocr textbook?
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    (Original post by hellosarah)
    1- Membrane bound receptors have a specific recognition site which has a complementary shape to this specific hormone or drug. Any cell with a receptor is called a target tissue.
    So the hormone/drug binds to the receptor on a target cell surface membrane, causing the target cell to respond in a particular way.
    Some medicinal drugs block receptors.

    2 + 3- Epithelial cells:
    Squamous epithelial tissue:
    - Thin, smooth, flat surface.
    - Provides a short diffusion pathway. E.g: in alveoli; for the exchange of oxygen and carbon dioxide.
    Cilliated epithelial tissue:
    - Made up of column-shaped cells; cillia.
    - Cillia wave in a synchronised rhythm to move mucus.
    E.g: in the breathing tract & moving egg cells along the oviduct.

    4 - A developing fetus obtains oxygen from its mother's blood and its own lungs.
    Oxygen arrives at the placenta in combination with haemoglobin.
    The partial pressure of oxygen in the blood vessels in the placenta is relatively low, as the fetus is respiring. Therefore, the mother's haemoglobin releases some oxygen, diffusing from the blood into the fetus's blood across the placenta.
    Partial pressure of oxygen in the fetus's blood is only a little lower than that in its mother's blood, meaning diffusion would occur at a very slow rate.
    BUTT this doesn't happen as fetal haemogblobin combines more readily with oxygen than adult haemoglobin.
    Fetal haemoglobin is said to have a HIGHER AFFINITY for oxygen than adult haemoglobin. So at any partial pressure of oxygen, fetal haemoglobin will take oxygen from adult haemoglobin.

    Does any of that even make sense? :confused:
    heyy ...yep it has helped especially 1,2 and 3. is 2 and 3 really that simple??..thought it would be complicated!! still a bit :confused: about 4 tho.
    thnx
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    (Original post by giraffegiraffe)
    ohhh yeah i see what you mean but gosh i hope not .. the not-straightforward questions are the worst! its so hard to try to realise what they want you to say. the pastpaper questions i've tried so far have been kindof straightforward in the way they're asked but its just getting those exact words in which is a killer!
    is everyone using the black and purple ocr textbook?

    using the cgp revision guide
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    (Original post by giraffegiraffe)
    is everyone using the black and purple ocr textbook?
    Yeah thats the one I'm using as well as the little thin revision guide to go with it. But the revision guide hasn't got enough information so I just tend to use it for last minute quick revision and the questions.
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    (Original post by pastpaper-guy)
    im just worried they will try to incorporate some of the syllabus into a real example. E.g they give you a question about the heart and talk about a kid who has a condition where the right atria has a hole in it.
    Explain why the kid feels tired alot of the time?


    not exactly like that but u get the point
    Regarding that hypothetical question they might ask you to intepret a Electrocardiograph (ECG) and the shape of it, PQSRT
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    (Original post by PhoTaydo)
    Regarding that hypothetical question they might ask you to intepret a Electrocardiograph (ECG) and the shape of it, PQSRT
    oh u reminded me. ecg was on my list.

    can someone explain what each letter is on a ecg diagram?

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    (Original post by pastpaper-guy)
    oh u reminded me. ecg was on my list.

    can someone explain what each letter is on a ecg diagram?
    P=atrial systole
    QRS=ventricular systole
    T=ventricular diastole

    (ie QRS and T are also atrial diastole)

    yup i'm using the cgp revision guide too, its surprisingly good for this course i think! along with the black and purple ocr book.
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    Another exam to **** up. Nice.
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    (Original post by pastpaper-guy)
    oh u reminded me. ecg was on my list.

    can someone explain what each letter is on a ecg diagram?

    ill talk about the unhealthy ones (this is in the book so i assume it could come up)

    elevation of the ST section is an indicator of a HEART ATTACK

    small & unclear P wave = ATRIAL FIBRILLATION -(dodgy heart beat pattern lol)

    deep S wave = abnormal ventricular hypertrophy (muscle thickness increases)
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    Some quick notes on the movement of water through the xylem.
    • Water moves into the xylem down a water potential gradient.
    • Pressure from water entering the xylem via osmosis gives the bottom of the xylem a high hydrostatic pressure.
    • Transpiration at the leaves creates a low hydrostatic pressure at the top of the xylem.
    • Water, under tension, is pulled up in a continious column.
    • This is aided by: cohesion - the attraction of water molecules to each other, forming hydrogen bonds.
    • adhesion - the attraction of water molecules to the xylem wall.
    • Capillary action also aids the process - this is where the water rises because it is placed in a very narrow tube.
    • All of the above bullet points lead to the water moving up the xylem by mass flow, from a higher hydrostatic pressure to a lower hydrostatic pressure, down a pressure gradient.


    Rep appreciated. :-)
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    Are things like heart block, ventricular fibrillation, bradycardia and tachycardia likely to come up? They're not in the book, but our teacher gave us a load of sheets which had those one?
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    Okay...in the black and purple ocr book, it says normal adult cells of most eukaryotes contain two sets of chromosomes..? so each set contains 23 chromosomes right?, so if we were asked to draw a diagram of this.., what would you do? am i missing something?
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    (Original post by TattyBoJangles)
    Are things like heart block, ventricular fibrillation, bradycardia and tachycardia likely to come up? They're not in the book, but our teacher gave us a load of sheets which had those one?
    i doubt it as they don't seem to give ECGs much emphasis in the book? i think probably what 786girl said about abnormal ECGs will be about it ?
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    Why is there always so little on the heart when it's the area i'm best at.
 
 
 
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