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

  • View Poll Results: Are you resitting this unit?
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    (Original post by Jin3011)
    Damn OCR and their stupidness. I've got the non-Mei exam
    Have you done much revision for it? I seem to be taking biology as my top priority when I know I need to do well in stats after I messed up C4 lol.
    Revision for S2 is alright, I feel. I don't think i've done too well on C4 either so have concentrated more on S2. As for Biology, I've still got the muscle bit to do, gene therapy, fingerprinting and regulation of transcrpition and translation.
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    (Original post by irn_bru)
    I have a book with 20 sample essays, and theres a title Lipids in health and disease which includes the following:
    Triglycerides (formed by condensation of glycerol and 3 fatty acids)
    Thermal insulators (so help in maintaining body temperature by homeostatis)
    As fuels (Hydrolysis of triglycerides by lipase enzymes releases fatty tissues which can be converted to respiratory substrates such as glucose in the process gluconeogenesis)
    Obesity (atheroma, myocardial infarction, risk factor in diabetes)
    Phospholipids (Fluid-mosaic model, hydrophilic heads, hydrophobic tails)
    Cholesterol (adds strength to membrane)
    Myelination of neurons (important in acceleration of nerve impulses).
    Thankyou soo much, i repped!!
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    (Original post by 123trident)
    Revision for S2 is alright, I feel. I don't think i've done too well on C4 either so have concentrated more on S2. As for Biology, I've still got the muscle bit to do, gene therapy, fingerprinting and regulation of transcrpition and translation.
    Quite a bit to do then. g'luck with that
    I'm just happy knowing that after this exam, we may never have to do an AQA bio exam again!
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    heyy wondering if someone could help....
    what kind od essay could you write for
    i) hydrogen
    ii) ions

    any help greatly appreciated && major rep for life!
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    (Original post by appleschnapps)
    You're welcome! Typing stuff up like this helps me too.

    Sliding filament theory: When an action potential stimulates a muscle cell (i.e. after a neuromuscular junction, it depolarises the sarcolemma (membrane of the muscle) and this depolarisation is carried down the T-tubules (formed by folds in the sarcolemma) to the sarcoplasmic reticulum. This causes the sarcoplasmic reticulum to release calcium ions into the sarcoplasm. The ions then bind to troponin, which changes its shape and so pulls the tropomyosin it is attached to out of the way. This exposes the actin-myosin binding site.

    The globular myosin head on the myosin protein has an ADP molecule attached. This allows the myosin head to bind to the actin and form a cross-bridge. The myosin head then changes its angle, causing the actin to move (or slide), and the ADP molecule is released. In its place an ATP molecule attaches, which then breaks the cross bridge. The calcium ions activate the enzyme ATPase, which hydrolyses the ATP to ADP and inorganic phosphate (so you have an ADP molecule attached to the myosin head again!), and the energy released allows the myosin head to return to its original angle, so the process can continue. It does this until nervous stimulation stops.

    When this happens, the energy released from the ATP is used to return the calcium ions to the sarcoplasmic reticulum (so this is an example of active transport). Without the calcium ions, the tropomyosin moves back into position and the binding site is no longer exposed, so the myosin heads can no longer form cross-bridges.

    http://i56.tinypic.com/if0bo3.png

    So, if that's our relaxed sarcomere, when it is contracted the actin filaments slide over the myosin.

    http://i51.tinypic.com/o0eclx.png




    The sarcomere itself is contracted, but the actin and myosin remain the same size. The actin filaments have just moved closer together. Normally when describing this contraction from diagrams, it gets split into different parts.

    http://i51.tinypic.com/izz2mg.png

    The A-band is where you have myosin and some actin, the H-zone is entirely myosin and the I-bands are entirely actin. When the actin slides over, the A-bands stay the same (because the myosin doesn't move, only the actin!), the H-zone gets smaller and the I-bands get smaller.

    http://i52.tinypic.com/npexau.png

    If you can stand the excitement, sometimes they don't label it and instead just use different light levels. Now, because myosin is thicker than actin, areas with myosin are darker than with actin - but because combined they're denser still, the darkest area has both myosin and actin. When the sarcomere contracts, the darkest area gets wider, and the light and medium-dark areas get narrower.

    ... So you know, like an hour later you get a response. Sorry!
    WOW! you really really do know your stuff!! I have another query
    what kind od essay could you write for
    i) hydrogen
    ii) ions

    youll probz be asleep but o thought i would take my chances. Thanks so much for all your help...... youll defo get an A! thank youuuuuuuuuu
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    (Original post by *QueenBeee)
    heyy wondering if someone could help....
    what kind od essay could you write for
    i) hydrogen
    ii) ions

    any help greatly appreciated && major rep for life!

    Hydrogen- helps to maintain the structure of the tertiary structure in enzymes.
    Bonds bases together in DNA.


    Ions

    Sodium- potassium pump
    Resting and action potential
    Calcium ions in transfer of nerve impulse across synapses.
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    (Original post by *QueenBeee)
    WOW! you really really do know your stuff!! I have another query
    what kind od essay could you write for
    i) hydrogen
    ii) ions

    youll probz be asleep but o thought i would take my chances. Thanks so much for all your help...... youll defo get an A! thank youuuuuuuuuu
    Hydrogen - mentioned above + Elec transport chain , coenzymes reduction of GP etc
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    ****.. I feel sleepy. I'm gonna head off now. I'll wake up at 5 and finish the rest. Cya guys.
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    Is there no jan 2011 paper? Apparently the only paper we have is june 2010?
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    Yep that's true. June is the only paper.
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    Anyone still here?
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    Yeah, im here and im struggling
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    Any ideas on essay titles ??
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    I'm dead, oh well might as well purchase those South Korea tickets then, my mum can't find me there when she sees my results...
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    My teacher said lipids but its really hard to predict as theres only 2 papers
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    Can someone help about siRNA?

    Ok how are double-stranded RNA molecules made? I know after it is cut to make siRNA and the separation, protein complex blah blah
    But how do they make the dsRNA in the first place?

    Thanks!!
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    This paper is gonnA BE suchh a *****hhh! anyone kno wat kinda mark youll need 4 a B ?
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    Double-stranded RNA (dsRNA) is RNA with two complementary strands, similar to the DNA found in all cells. dsRNA forms the genetic material of some viruses (double-stranded RNA viruses). Double-stranded RNA such as viral RNA or siRNA can trigger RNA interference in eukaryotes, as well as interferon response in vertebrates.
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    (Original post by sunil10)
    This paper is gonnA BE suchh a *****hhh! anyone kno wat kinda mark youll need 4 a B ?
    Not sure about mark but going from last years paper, probably about 55/100.
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    (Original post by sunil10)
    This paper is gonnA BE suchh a *****hhh! anyone kno wat kinda mark youll need 4 a B ?
    Last year it was 55 out of 100 for a B
    BUt thats the only past unit 5 paper
 
 
 
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