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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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    someone please explain gel electropherisis? :/
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    (Original post by hiyarearl)
    If I post up an essay I just had a go at could someone read it and maybe suggest what sort of marks I'd have gained/where there are errors or what I could add to it?

    How long should the essay be and in what detail should each topic with it be discussed? The essay below took me about 30 minutes or so to plan and write and took up 2 1/2 sides of A4
    Your essay pretty much covered all the main points. The idea is to go into enough detail for the examiner to think you know your stuff well, but not to end up waffling over the same point for too long. Two sides is fine, although my teacher showed us one person's essay from a previous exam where she wrote 7 sides! How you can write seven pages in max 45 minutes is beyond me!!

    Another tip: do a plan before starting the main essay - examiners are obliged to mark your plan, and they give credit if you've mentioned something in your plan, which you've left out of your main essay (as long as it's relevant!)
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    (Original post by golddust&lipgloss)
    someone please explain gel electropherisis? :/
    GF is used to spearate DNA fragments according to their length:

    1. Place the DNA fragments in a little well at one end of an agar plate.
    2. Apply a voltage across both ends of the agar gel.
    3. The negatively charged phosphate group is attracted towards the positive cathode
    4. Smaller fragments travel further and faster in a set time - the order of fragments determines the DNA sequence.


    Hope this helps
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    (Original post by ben10)
    hey do you have the essay booklet online? if so please could i have a copy

    Im so sorry, but i dont! Our teacher gave us the booklet! Im sure if you googled you could find them!
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    (Original post by xelaman)

    QS: Explain the role and action of transcriptional factors.
    Where does it say on the spec we need to know about them!!
    Are they them things that cause the stuff thats blocking some enzyme that allows for a particular bit of DNA to be transcribed?

    If they are, they can be involved in the specailisation of cells?

    Tell tell!
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    (Original post by ben10)
    does anyone know how too calibrate the gel electropherisis.. ?
    you could put in dna strand of known lengths to see how far they go to compare againts.
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    is it me or is there so many stages in bio 5, **** loads...

    hvent really practiced essays, any1 got any tips and how to tell if essay is gd

    many thanks :P
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    ShortQuestion: Explain the role of phosphocreatin in muscle contraction.
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    (Original post by kingsmod1)
    is it me or is there so many stages in bio 5, **** loads...

    hvent really practiced essays, any1 got any tips and how to tell if essay is gd

    many thanks :P
    I dont think it is as daunting as people make it out or it could just be my Biology teacher making our class to relaxed :/, but just put through 4/5 strong points in detail and you have your marks in a bag. I think its a bad idea doing loads of questions because the essay is all about your knowledge and how in depth it is not the way you right essays. So im preparing by looking over some of the main concepts of unit 4 unit 2 and unit 1.
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    (Original post by Ramin Gorji)
    I dont think it is as daunting as people make it out or it could just be my Biology teacher making our class to relaxed :/, but just put through 4/5 strong points in detail and you have your marks in a bag. I think its a bad idea doing loads of questions because the essay is all about your knowledge and how in depth it is not the way you right essays. So im preparing by looking over some of the main concepts of unit 4 unit 2 and unit 1.
    Do you have any essay questions I could practice, NOT from the specimen or 2010 june paper?

    When ever I see a question i can think of a sentence to answer it and thats it.
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    (Original post by emmaaa65)
    your essay is really good!! it makes me depressed about how bad my essays are! haha, ermm im not too sure what mark you would gues, but it seems like you have literally covered ATLEAST one thing from each unit so well done! im going to have to start revising more for this essay i havent even finished revising for unit 5 :afraid:
    Thanks. Don't worry, even if I can do the essays(ish) I have about 1/2 of unit 5 to still revise! Oh well, will just have to work SUPER hard. Good luck and I'm sure you'll get better with practice! How much have you covered for bio5 so far?
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    Edit: Oops, my bad for double post!

    (Original post by Seasick Steve)
    Your essay pretty much covered all the main points. The idea is to go into enough detail for the examiner to think you know your stuff well, but not to end up waffling over the same point for too long. Two sides is fine, although my teacher showed us one person's essay from a previous exam where she wrote 7 sides! How you can write seven pages in max 45 minutes is beyond me!!

    Another tip: do a plan before starting the main essay - examiners are obliged to mark your plan, and they give credit if you've mentioned something in your plan, which you've left out of your main essay (as long as it's relevant!)

    Thanks for the advice. I'll try not to waffle too much, I guess letting the examiner know I know my stuff is the important bit - doing too much could also lead to mistakes in my explanations being picked out too, which wouldn't be good ! 7 sides seems pretty rediculous in 45 minutes, they must have finished the paper very quickly! I'll make sure I plan properly as I have a bad tendency to just start writing and see where it leads.
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    (Original post by Destroyviruses)
    ShortQuestion: Explain the role of phosphocreatin in muscle contraction.
    If I remember:

    Phosphocreatine stores are an adaptation of a fast-twitch muscle fibres. Fast twitch muscle fibres are adapted for intensive exercise and so respiring muscles in this situation require such vast quantities of ATP that the rate of aerobic respiration and hence the oxygen required exceeds that of what can be delivered to the respiring muscle by the blood. This results in anerobic respiration which means ATP cannot be reformed as most ATP is regenerated from ADP during the respiration of pyruvate i the mitochondria which requires oxygen. Phosphocreatine acts as an additional source of inorganic phosphate molecules that can be combined with ADP to reform ATP providing energy for muscle contraction. When the muscle relaxes this store of phosphate is replenished via the breakdown of ATP into ADP and phosphate.
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    (Original post by hiyarearl)
    If I remember:

    Phosphocreatine stores are an adaptation of a fast-twitch muscle fibres. Fast twitch muscle fibres are adapted for intensive exercise and so respiring muscles in this situation require such vast quantities of ATP that the rate of aerobic respiration and hence the oxygen required exceeds that of what can be delivered to the respiring muscle by the blood. This results in anerobic respiration which means ATP cannot be reformed as most ATP is regenerated from ADP during the respiration of pyruvate i the mitochondria which requires oxygen. Phosphocreatine acts as an additional source of inorganic phosphate molecules that can be combined with ADP to reform ATP providing energy for muscle contraction. When the muscle relaxes this store of phosphate is replenished via the breakdown of ATP into ADP and phosphate.
    Yey welldone! You said so much. I'm probably say something dumb like, the phrovide phospates to change ADP back ATP, 'nuf said! And lose A LOAD of marks!
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    (Original post by parallal)
    I don't know if anyone has posted anything like this but here are some condensed notes I made. Hope they're helpful (If there is already notes then just let me know and I'll take these down)
    They're not perfect so if there's anything I missed out or anything like that let me know

    I'll add the notes on genes as soon as I'm done with them.
    Thanks so much! Superstar!
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    Just looked at the spec and it says " The technique of genetic fingerprinting .... and its use in determining the genetic variability within a population."

    what does this mean?! and how would you determine the variability?
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    (Original post by parallal)
    I don't know if anyone has posted anything like this but here are some condensed notes I made. Hope they're helpful (If there is already notes then just let me know and I'll take these down)
    They're not perfect so if there's anything I missed out or anything like that let me know

    I'll add the notes on genes as soon as I'm done with them.
    Hi, about your muscle contraction notes.

    You've put that initially there is an ATP attached to the myosin head but according to the textbook. Initially it is ADP.The myosin moves and then the ADP is released. THEN ATP joins with myosin to remove it from the actin and but the head back in the "cocked" position. Then atpase hydrolysis ATP to ADP so its able to join to actin again.

    I just double checked on the textbook.
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    Yeah, myosin has the ADP attached initially. Ca2+ binds to troponin, causing the tropomyosin to shift and open up binding sites on actin for the myosin.

    Myosin bulbous heads bind to actin. They release the ADP and as they do so the angle of the myosin head changes. ATP binds to the actin head, meaning it detaches.

    ATP is hydrolysed to provide the energy for the myosin head to return to its original angle, leaving ADP attached in preparation for the next cycle.
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    (Original post by hiyarearl)
    Thanks. Don't worry, even if I can do the essays(ish) I have about 1/2 of unit 5 to still revise! Oh well, will just have to work SUPER hard. Good luck and I'm sure you'll get better with practice! How much have you covered for bio5 so far?
    i finished going over chapter 13 yesterday which im still struggling with but ohwell!
    im going to start going over chapter 14 today and hopefully get all the genetics stuff out of the way by the middle of this week... i hate chapters14-16 theyre so long!!!
    after thats done im going to go over past exam papers and all that stuff!
    this exam is getting to close! :eek:
 
 
 
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