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AQA BIOL1 Biology Unit 1 Exam - 16th May 2011 watch

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    Many different substances enter and leave a cell by crossing its cell surface membrane. Describe how substances can cross a cell surface membrane. (5 Marks)
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    (Original post by EffKayy)
    PanicPanicPanicPanic!!!!!!!!!! I THOUGHT I KNEW MOST OF THE STUFF! I DON'T!!!!!
    What dont you know? : O
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    (Original post by EffKayy)
    For the alveoli, it is essential to say the walls are folded to give a large surface area as the june 2010 paper only allowed that.
    aww, dont worry mate.. i feel exctly the same.. infact i am!! ur not alone, wer in the same boat!!
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    (Original post by TlanTlan)
    For secondary response i put it as:

    There are already many memory cells from a previous infection by a pathogen, and these "remember" the antigen, so during the secondary response more antibodies are produced a lot quicker and these neutralise a pathogen and its toxins before symptoms of a disease begin to appear.

    I use a mixture of nelson thornes and CGP. Then i do all the past papers as both of them use words that AQA don't!
    Think you need to know differences between T memory and B memory cells I think.
    I think T killers remember the shape of antigens and B memory remember how to produce the antibodies to neutralise the antigens.
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    (Original post by swiftylol)
    What dont you know? : O
    I feel like i don't, when I do?!?! I really don't know.

    I'm just quite paranoid i'll forget everything..
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    (Original post by TlanTlan)
    Many different substances enter and leave a cell by crossing its cell surface membrane. Describe how substances can cross a cell surface membrane. (5 Marks)
    Small non-polar substance can enter through the phospholipid bi-layer through diffusion. Those that are too large, eg glucose or polar have to use carrier proteins which is facillitated diffuision and is a passive movement so requires no energy.

    Any examples of polar substances? Is it ions?
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    (Original post by EffKayy)
    I feel like i don't, when I do?!?! I really don't know.

    I'm just quite paranoid i'll forget everything..
    Don't just read over everything, make questions for each chapter and see if you can answer. Questions just testing the content of your own notes. That's what I'm doing.
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    (Original post by TlanTlan)
    Many different substances enter and leave a cell by crossing its cell surface membrane. Describe how substances can cross a cell surface membrane. (5 Marks)
    Simple diffusion - net movement of a molecule/ion from a high concentration to a low concentration down a concentration gradient.
    Facilitated diffusion and active transport requires carrier proteins.
    In the phospholipid bilayer, lipid-soluble molecules can pass through it, whereas water-soluble ones come through protein carriers.
    Active transport - against a concentration gradient, requires ATP and carrier proteins/co-transport mechanism. Sodium potassium transport?!?
    Osmosis - movement of water from a high water potential to a low water potential through a partially permeable membrane.

    I really d on't know what i've wrote!
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    (Original post by jones_wise)
    Correct. That would be enough to get all three marks.
    I've learnt that in this unit being simple gets you the marks :P
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    (Original post by EffKayy)
    Simple diffusion - net movement of a molecule/ion from a high concentration to a low concentration down a concentration gradient.
    Facilitated diffusion and active transport requires carrier proteins.
    In the phospholipid bilayer, lipid-soluble molecules can pass through it, whereas water-soluble ones come through protein carriers.
    Active transport - against a concentration gradient, requires ATP and carrier proteins/co-transport mechanism. Sodium potassium transport?!?
    Osmosis - movement of water from a high water potential to a low water potential through a partially permeable membrane.

    I really d on't know what i've wrote!
    I think simple diffusion is only small, lipid soluble, non polar molecules (i.e. not ions.) Ions pass through ion channels.
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    (Original post by liviaaa)
    No, that's not right. It goes into the blood. Look at June 09, question 7b.
    Bloody hell guys! i thought the same as tlantlan. thank god i checked this! i had to read over my notes again and realised ive written it down wrong this whole time! PHEWWWWWW
    if this comes up then i know who to thank
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    (Original post by EffKayy)
    I feel like i don't, when I do?!?! I really don't know.

    I'm just quite paranoid i'll forget everything..
    Just think, in 24hrs this exam will be over :/
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    (Original post by ??????????????????)
    Think you need to know differences between T memory and B memory cells I think.
    I think T killers remember the shape of antigens and B memory remember how to produce the antibodies to neutralise the antigens.
    I think the main difference is B cells make anti bodies and T cells don't. Both remember the "shape" as both have to bind to kill/produce antibodies.
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    (Original post by liviaaa)
    I think simple diffusion is only small, lipid soluble, non polar molecules (i.e. not ions.) Ions pass through ion channels.
    In the NT book it says molecules OR ions! ?

    Thanks though.
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    (Original post by swiftylol)
    Just think, in 24hrs this exam will be over :/
    YAY But then maths...
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    (Original post by EffKayy)
    In the NT book it says molecules OR ions! ?

    Thanks though.
    I don't think so.. :s
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    (Original post by ??????????????????)
    Small non-polar substance can enter through the phospholipid bi-layer through diffusion. Those that are too large, eg glucose or polar have to use carrier proteins which is facillitated diffuision and is a passive movement so requires no energy.

    Any examples of polar substances? Is it ions?
    yeah i think its ions like K+, Na+, etc. but im not sure....
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    (Original post by liviaaa)
    I think the main difference is B cells make anti bodies and T cells don't. Both remember the "shape" as both have to bind to kill/produce antibodies.
    Yeah thought so. Thanks for comfirming it though
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    Hi, can anyone tell me how I would answer this question in simple terms if this came up as a 6-7 mark question in the exam. 'Describe how water moves from roots to leaves?' Or something like that.. I always end up waffling!!

    I'm having trouble with transports in plants :mad: Also, if anyone can explain how sucrose is loaded into the phloem that would be great also!
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    Hi i'm doing this exam but i'm really stuck on something
    the bronchi and other parts of the lung have smooth muscle but what is this ?
    is this the elastic tissue which controls the blood flow ?

    Please Help
 
 
 
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