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

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    (Original post by Ambitions)
    Why do vaccines need to be continually updated? Apart from mutations... (for a 3 mark question say? )
    Could pathogens become resistant to the vaccine? Like, they adapt so that the antibodies produced by the plasma cells, which will have formed from the memory cells, are no longer complimentary and are ineffective? I'm really not sure about that though, probably making up biology.
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    (Original post by fluker6696)
    Quick query, in the Jan 2013 paper there was a question on the number of species in the world. I put that speciation is an ongoing process and so the number of species is constantly increasing, yet the mark scheme specifically said 'IGNORE refs to speciation' and accepted 'concept of species, difficult to define' (BS). Anyone know why this was the case? Ignoring the quality of OCR's exam writers :rolleyes: ...
    Speciation would take too long so wouldnt have affected this

    concept of species, difficult to define refers to it being different to differentiate between grasses for example, they may have grouped grass into a general group but really there are many different types of grass- although it is difficult to define how many
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    How would you describe the global impact of HIV/T.B/Malaria??

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    (Original post by kited4)
    What is the chance we could get a long question (8) marks comparing the action of B and T lymphocytes?

    - that would give us the chance to talk about T mature in thymus, B have antibodies on the surface but T have receptors, T action kills other cells but B doesnt, both produce memory cells
    and stuff like that?

    that would be a fab question
    Agreed


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    Explain the three different types of adaptation 6marks
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    Guys why is the induced fit hypothesis a better theory than the lock and key hypothesis? ( Btw is it hypothesis or model?)
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    (Original post by YouKnowMyName)
    Explain the three different types of adaptation 6marks
    Behavioural adaptation - an aspect of an organsism where its behaviour helps it to survive
    e.g. a worm when touched coils up even though it doesn't have any eyes to protect itself (isnt that cute?)

    Biochemical adaptations - How its biochemistry enhances survival so yeast cells respire anaerobically

    Anatomical - Structural adaptations
    So sperm cells have flagella that help it to move
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    (Original post by Beni24)
    Guys why is the induced fit hypothesis a better theory than the lock and key hypothesis? ( Btw is it hypothesis or model?)

    There is more evidence which supports it and it explains why the activation is lowered when the enzyme is present
    i tend to say model but i dont think it matters x
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    (Original post by Beni24)
    Guys why is the induced fit hypothesis a better theory than the lock and key hypothesis? ( Btw is it hypothesis or model?)
    Because it helps scientists understand why substrate molecules that are not exactly complementary to the active site of an enzyme still form enzyme substrate complexes....because the active site slightly changes it shape

    And its hypothesis
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    (Original post by HeyMickey6)
    i would say starch is made from amylose and amylopectin which both form alpha helix structures, not just starch is coiled.

    You may not get the mark for saying coiled cause you can have a left handed helix which is the structure collagen
    Oooh okay thanks
    What IS amylopectin?
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    (Original post by Beni24)
    Guys why is the induced fit hypothesis a better theory than the lock and key hypothesis? ( Btw is it hypothesis or model?)
    Its a model because it illustrates how an enzyme actually works.

    The induce fit model provides a better theory because it explains how an enzyme act as a biological catalyst, helping to speed up a chemical reaction.

    Thats what I would say, I believe it to be correct :bl:
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    (Original post by greatwhiteshark)
    An organism that carries a disease from one host to another.
    So a mosquitto would be a vector?
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    Go on the Human Biology Spec June 2012 Past paper, they asked that question so you may want to memorise mark scheme
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    Hi
    If I have an A in my coursework and I do bad and get a D for unit 2 (hopefully this won't happen) do they bring ur coursework grade down ? Or will it stay an A

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    (Original post by HelenPaddock)
    Something that transports a disease/pathogen (eg the mosquito is the vector for the plasmodium pathogen)
    Legend. Here have a thumbs up.
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    I'm feeling a bit better about this now- I've been using the technique for answering that I saw in one of the reports, and I feel like I don't start to panic-write answers :P Might be a different story at 11am tomorrow though.

    Good luck to everyone sitting it tomorrow
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    (Original post by rival_)
    So a mosquitto would be a vector?
    Yeah a mosquito is a vector.
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    (Original post by samiwami)
    Oooh okay thanks
    What IS amylopectin?
    Amylopectin is a long branched chain of alpha glucose. It's side branches allow the enzymes that break down the molecules to get the glycosidic bonds easily. This means that the glucose can be released quickly
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    Hi, this is not mentioned in my book but the mark scheme says it. Just wondering if any of you can confirm whether it is true. It says that when memory cells detect their specific antigen/pathogen then they differentiate into plasma cells, which release the antibodies that neutralise the foreign pathogen.

    I didn't realise that memory cells can turn into plasma cells. What else can they do?
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    (Original post by samiwami)
    Oooh okay thanks
    What IS amylopectin?
    Starch consists of amylose and amylopectin. Amylopectin has the same structure as glycogen apart from its present in plants and glycogen in present in animals.

    Amylopectin is,
    -branched
    -has 1-4 and 1-6 glycosidic bonds
    etc same as glycogen
 
 
 
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