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

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    (Original post by MarkProbio)
    I don't understand how people can come on here saying they are 100% of the answer. I believe this was a suggest question, was it not? Either way, there is often more than 2 points that are valid for a 2 mark question.

    I haven't googled the water bear so perhaps you know more about this than me, and having looked around it seems the microscope - in its early stages - has been around since 1595, not to mention the fact the Romans used glass in experiments. That said, unless you are near certain and have some proof to back your case up, I wouldn't scare people so much by saying their answer is 100% wrong.

    It was an electron microscope though, which isn't an "early form"
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    (Original post by sh7171)
    What did people write for the question to do with ethanol and toxins?
    First of all I put that the enzyme can break down both because they both contain an alcohol group -OH.

    For the next part I said if there is a higher concentration of ethanol in relation to DEG then that is the substrate in excess and is more likely to be broken down than the enzyme due to its high concentration meaning the enzymes can't focus on breaking down the DEG and thus less of the toxin is released.
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    (Original post by MarkProbio)
    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.
    I wrote all that but though it was too short and began to talk about b-cells and antibodies, would I loose marks for including the second bit
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    (Original post by MarkProbio)
    I don't understand how people can come on here saying they are 100% of the answer. I believe this was a suggest question, was it not? Either way, there is often more than 2 points that are valid for a 2 mark question.

    I haven't googled the water bear so perhaps you know more about this than me, and having looked around it seems the microscope - in its early stages - has been around since 1595, not to mention the fact the Romans used glass in experiments. That said, unless you are near certain and have some proof to back your case up, I wouldn't scare people so much by saying their answer is 100% wrong.
    I was debating whether to write about evolution or microscope, but then microscope is in unit 1 so I thought I would just go for evolution

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    (Original post by jackitsme)
    i did R1 as the same...R2 one the same and second band higher

    for valid i wrote-same suger concentration,same number of spins and rate and volume of dna the same

    i put conc of sugar thing
    volume of sugar thing
    how long it is left to spin and same speed


    others could be -temp? volume/length of DNA
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    What were the 3 reasons for low income groups being more likely to get TB?
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    (Original post by niceguy95)
    I wrote all that but though it was too short and began to talk about b-cells and antibodies, would I loose marks for including the second bit
    Same I did that too... hopefully they'll just ignore right??
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    First microscope was invented in 1590
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    (Original post by student_1995)
    It said it was a vertebrate so it is animal
    http://en.wikipedia.org/wiki/Tardigrade

    Tardigrades (commonly known as waterbears or moss piglets)[2] are small, water-dwelling, segmented animals with eight legs.
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    (Original post by Sam_1996)
    What were the 3 reasons for low income groups being more likely to get TB?
    I wrote poor living conditions, overcrowding, and not steralising water
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    (Original post by Liamnut)
    Macrophages dont as far as Im aware. It's the infected cells.
    Ah that's what I meant, my bad
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    (Original post by Sam_1996)
    What were the 3 reasons for low income groups being more likely to get TB?
    I wrote about overcrowding due to smaller houses, can't afford for healthcare and likely to live in polluted area.... hope this is right:s

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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 wrote the exact same thing! I don't understand how others have managed to get lymphocytes out of the questions FFs. Did I read it wrong or something. Then again I guess it was too easy for 7 marks
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    (Original post by rival_)
    The question about why complementary based pairing is important was hard, asexual selective reproduction was just a myth lol
    Weird right.. Which kingdom did you put that silly bear thing into


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    (Original post by Sam_1996)
    What were the 3 reasons for low income groups being more likely to get TB?
    Lack of money means
    Poor ventilation
    Poor diet
    Overcrowding in small houses
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    it's microscopic organism , so evolution happen faster due to short lifespan , it's not a dinosaur to evolve in million years is it !!!
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    (Original post by Sam_1996)
    What were the 3 reasons for low income groups being more likely to get TB?
    more likely to have
    - poor diet
    - HIV/AIDS (weakened immune system)
    - poor housing (overcrowding)

    then I guess things like poor ventilation etc
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    (Original post by Sam_1996)
    What were the 3 reasons for low income groups being more likely to get TB?
    overcrowding
    poor diet
    poor ventilation


    poor working conditions
    poor health-i.e HIV more likely to get it due to weakened immune system
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    Thumbs up if you failed? Thumbs down if you think you done well?
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    (Original post by Sam_1996)
    What were the 3 reasons for low income groups being more likely to get TB?
    I wrote less education therefore less knowledge about how it's spread.
    Overcrowded living conditions
    Poorer countries I.e. Africa, more people have aids therefore more susceptible to tv
 
 
 
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