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AQA BIOL5 Biology Unit 5 Exam - 22nd June 2011 Watch

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    (Original post by angel1992)
    can hormones be lipids, carbs, proteins any?
    proteins and lipids, in this we have to know that oestrogen is lipid so can pass though membrains and insulin and adrenaline are protein and so can not pass though membrain so use 2nd messenger model
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    (Original post by bobsaeed)
    proteins and lipids, in this we have to know that oestrogen is lipid so can pass though membrains and insulin and adrenaline are protein and so can not pass though membrain so use 2nd messenger model
    thankyou, i see the link now between the 2nd messenger model!!!!!!!!
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    do stem cells regenerate themselves, i dont get it, if you insert a gene into a stem cell, why dont you need to periodically supplement more??????
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    are plasmids in cystic fibrosis treatment inserted into the adenovirus with the healthy cftr gene?
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    June 2010 I don't get 3.c I thought potassium ions move out in the end causing repolarisation?
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    (Original post by angel1992)
    do stem cells regenerate themselves, i dont get it, if you insert a gene into a stem cell, why dont you need to periodically supplement more??????
    Because
    - adult stem cells are not as robust at embryonic stem cells and may not last as long.
    - the body might reject the foreign cell
    - the gene may not be expressed in sufficient quantities (due to unknown factors)
    - in SCID the T-cells are involved in the immune response and are "used up"


    (Original post by angel1992)
    are plasmids in cystic fibrosis treatment inserted into the adenovirus with the healthy cftr gene?
    Yes.
    Either
    - the healthy cftr gene is inserted into an adenovirus vecto (ie. the adenovirus genome), which is then inserted into the defective cells
    or - the healthy cftr gene is inserted into a plasmid vector, which is enclosed in a liposome (lipid vesicle), then inserted into healthy cells.
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    I hope the essay is on a unit 5 topic, that way we can get a lot of the unit 5 in and a bit of the other units too if we can. If it's unit 5 we only be able to write about a limited number of things then it's better imo. :p:
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    (Original post by angel1992)
    are plasmids in cystic fibrosis treatment inserted into the adenovirus with the healthy cftr gene?
    Yeah, then the adenovirus inserts the functional CFTR gene into the epithelial cells. They can also be wrapped in lipid molecules so form a lisosome which can then pass across the phospholipid bilayer of the epithelial cells by diffusion.
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    (Original post by Sparkly-Star)
    June 2010 I don't get 3.c I thought potassium ions move out in the end causing repolarisation?
    Yeah! I saw that yesterday! I reckon it's a mistake in the mark scheme, cause all the text books say it's the movement of potassium ions out of the axon that causes repolarisation.
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    (Original post by laura123)
    Yeah! I saw that yesterday! I reckon it's a mistake in the mark scheme, cause all the text books say it's the movement of potassium ions out of the axon that causes repolarisation.
    *Phew* cos in the previous answer we had to write that potassium ions move out as well so yeah I hope it is a mistake.
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    Hey guys...

    The thing is, i think i know my stuff (hopefully!) but im struggling being able to apply it to exam questions...like not being too sure on what the questions asking.

    Anyone got any advice plz?

    Thanks. Gd luck!
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    (Original post by Zakir)
    Hey guys...

    The thing is, i think i know my stuff (hopefully!) but im struggling being able to apply it to exam questions...like not being too sure on what the questions asking.

    Anyone got any advice plz?

    Thanks. Gd luck!
    Look at loads of exam papers and markschemes...might help
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    (Original post by SkyHunter)
    Look at loads of exam papers and markschemes...might help
    yeah i know...but most of the q's are the old spec, and some of the answers don't make sense!!

    :confused:
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    Can anyone please explain kineses?
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    Hey I am planning an essay on shapes of cells relating to their function. Can anyone help me out and give me some topics that i could talk about.

    TIA.
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    (Original post by bobsaeed)
    proteins and lipids, in this we have to know that oestrogen is lipid so can pass though membrains and insulin and adrenaline are protein and so can not pass though membrain so use 2nd messenger model
    Hormones are all proteins, and oestrogen is lipid SOLUBLE, not a lipid... it says this in nelson thornes.
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    I dont think theres much point in planning an essay, because it could be on anything! Best to focus on going through notes the day before i think..
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    can someone help explain to me the all-or-nothing principle please, I'm finding it difficult to understand. Thanks.
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    (Original post by User12399)
    can someone help explain to me the all-or-nothing principle please, I'm finding it difficult to understand. Thanks.
    If the strength of the stimulus does not reach OR exceed the threshold of the neurone, an action potential will not be generated due to not enough sodium ion channels opening meaning the membrane is not depolarised enough to cause more sodium channels to open further down the axon.
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    (Original post by TlanTlan)
    If the strength of the stimulus does not reach OR exceed the threshold of the neurone, an action potential will not be generated due to not enough sodium ion channels opening meaning the membrane is not depolarised enough to cause more sodium channels to open further down the axon.
    thanks, is that all we need to know?
 
 
 
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