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

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    (Original post by nasira372)
    Cardiac cycle

    atrial systole-Atria contract. Pressure in the atria is higher than in the ventricles so the AV valves open causing the blood to move out of the atria
    and into the ventricles. Atria volume decreases, ventricles volume increases

    Ventricular systole-Ventricles contract from base up. Pressure in the ventricles is higher than the atria so the AV valves close to stop backflow. The pressure is the ventricles is also
    higher than the aorta so the SL valves open causing the blood to move into the aorta. Volume in the ventricles decreases, volume in the aorta increases

    Diastole-Both ventricles and atria relax. Pressure is low

    Could anyone tell me if this is enough for the whole of the cardiac cycle. Also, does anyone know what is happening to the AV and SL valves at diastole (are they open or closed). Thanks
    Think you should mention that in diastole, the walls of the ventricles and atria are relaxed, hence the pressure in the ventricles in lower than in the aorta and P. artery and hence the semi-lunar valves shut. I think that AV are open during diastole.
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    (Original post by GottaLovePhysics! :))
    Ugh, feeling fine about the exam but only just found out there are answers to the examination questions in the AQA book!
    ****! Why didnt they put the answers in the book the ****'s!

    Also, why is Unit 2 a doss when Unit 1 has the immunology questions (which seems to be the harest part of the course)
    Immunology hardest part? Nah hearts hardest part for me :P

    Unit 2 is the only unit i haven't had to resit because i miraclously got an A first try....its supposed to be harder than Unit 1 but this is my second time resitting this damned unit now.
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    Hi guys I was just wondering for the non reducing sugar test when you add sodium hydrogen carbonate why do you have to add it slowly ? Doubt it will come up bit you never know with aqa ! Good luck guys x
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    (Original post by Tericon)
    Can anyone please help with this...its maths and my brain just shuts down:

    Calculate how much risk is increased by smoking 25 a day compared with not smoking at all:

    Not smoking: 0.17 25 a day: 4.17
    If your asking in % change then its the difference / original * 100
    So in this case its 4/0.17 * 100 = 2352.9 % increased chance

    If your asking how many times higher it is, you just divide 4.17 by 0.17 = 24.53
    24.53 Times higher risk.

    Hope that helps, correct me if im wrong
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    (Original post by animal*nature)
    Hi guys I was just wondering for the non reducing sugar test when you add sodium hydrogen carbonate why do you have to add it slowly ? Doubt it will come up bit you never know with aqa ! Good luck guys x
    Sodium hydrogen carbonate is an alkali so it neutralises the hydrochloric acid used to break the glycosidic bonds in the non-reducing sugars which causes them to become reducing sugars. I can only think you add it slowly to make sure you don't make the solution alkali instead of neutralising the HCL.
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    (Original post by animal*nature)
    Hi guys I was just wondering for the non reducing sugar test when you add sodium hydrogen carbonate why do you have to add it slowly ? Doubt it will come up bit you never know with aqa ! Good luck guys x
    Would like to know answer to that too, as you seem to know about that can i pick your brains?

    So with non-reducing, if its a positive result, it could be reducing still....why is this? Why does reducing test have to be done to rule out it being a reducing?
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    (Original post by Tericon)
    Can anyone please help with this...its maths and my brain just shuts down:

    Calculate how much risk is increased by smoking 25 a day compared with not smoking at all:

    Not smoking: 0.17 25 a day: 4.17
    i think you just do

    4.17 - 0.17 = 4

    then 4/4.17 X 100 = 95.92% ???
    or you do 4/0.17 X100 but that would give you 2352.94 % which seems too big.. i dunno
    im rubbish at maths
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    Why is the Secondary immune response much QUICKER and GREATER than the primary immune response?
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    I would actually cry if most of the exam turned out to be on lungs
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    (Original post by Tericon)
    Can anyone please help with this...its maths and my brain just shuts down:

    Calculate how much risk is increased by smoking 25 a day compared with not smoking at all:

    Not smoking: 0.17 25 a day: 4.17
    For any increase/decrease equation remember the following:

    (Difference/original) x 100

    So in this case:

    (4.17 - 0.17) / 0.17 x 100 = 2353 % (What? So high? )
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    (Original post by nasira372)
    If your asking in % change then its the difference / original * 100
    So in this case its 4/0.17 * 100 = 2352.9 % increased chance

    If your asking how many times higher it is, you just divide 4.17 by 0.17 = 24.53
    24.53 Times higher risk.

    Hope that helps, correct me if im wrong
    Looks good to me thanks, I was thinking all you had to do was take 0.17 from 4.17....but thats just the difference I hate that we have to cope with bits of maths in Biology

    Thanks everyone, there isn't enough rep to go around
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    (Original post by animal*nature)
    Hi guys I was just wondering for the non reducing sugar test when you add sodium hydrogen carbonate why do you have to add it slowly ? Doubt it will come up bit you never know with aqa ! Good luck guys x
    maybe to make sure you dont OVERneutralise it making it become an alkaline solution instead of neutral?
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    (Original post by emmaaa65)
    i think you just do

    4.17 - 0.17 = 4

    then 4/4.17 X 100 = 95.92% ???
    or you do 4/0.17 X100 but that would give you 2352.94 % which seems too big.. i dunno
    im rubbish at maths
    You divide the 4 by 0.17, not 4.17
    95% increase seems a little low because 100% doubles the figure to 0.34 which is nowhere near 4.17
    2352.94% is correct
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    (Original post by Insanity514)
    Why is the Secondary immune response much QUICKER and GREATER than the primary immune response?
    Because in the secondary response memory cells are already developed, so they will be able to recognize the antigens on the pathogens straightaway. Whereas in the primary response they will have no memory cells developed against the pathogen so they have to go through the whole process of T - cells and B - cells placing the antigens of the pathogen on their cell - surface membranes in order to produce plasma and memory cells which is a slower process.
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    On the specification, we are required to know 'The essential difference between humoral and cellular responses as shown by B cells and T cells.' As a revision exercise, would anyone be willing to give a short summary of what we would be required to know? Many thanks.
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    (Original post by emmaaa65)
    maybe to make sure you dont OVERneutralise it making it become an alkaline solution instead of neutral?
    Yeah that's a good point cos you would want to check the pH with pH paper as you're doing it.
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    Heres a quick question

    How do ventillation and circulation maintain a difference in concentration
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    (Original post by Tericon)
    Would like to know answer to that too, as you seem to know about that can i pick your brains?

    So with non-reducing, if its a positive result, it could be reducing still....why is this? Why does reducing test have to be done to rule out it being a reducing?
    I suppose with non reducing test it could still be a reducing sugar but that is why you do the reducing sugar test first to prove that it it is not a reducing sugar heat it with benedicts reagents and it will stay blue.
    To prove it is a non reducing sugar add hcl to hydrolyse any disaccharides into it's constituent monosaccharides and then add Sodium hydrogencarbonate to neutralise and retest with benedicts you will see a red ppt If non reducing sugar is present for example sucrose hope that helps xx
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    People are revising for this when there are two English exams looming ahead of them before Biology? :eyeball: I'm leaving revision for this 'til Wednesday!
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    (Original post by und)
    People are revising for this when there are two English exams looming ahead of them before Biology? :eyeball: I'm leaving revision for this 'til Wednesday!
    What exam are you on about this is AS Level Unit 1 biology. The exam is first thing tomorrow morning.
 
 
 
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