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    (Original post by Zoze)
    Hi, just wondering if someone can clarify this question about neurones to me. http://biogishumerus.com/2013/04/25/...s-past-papers/ Just click the link and click on nerves and hormones, scroll down and it's the pacinian corpuscle question from 2008.

    I don't really understand how a change in p.d is caused in the sensory neurone at light and medium pressures? surely the voltage gated sodium ion channels in the sensory neurone membrane don't open until the threshold value is reached? So are there other sodium ion channels that open in response to the generator potentials in the sensory receptor cell membrane? Just one final thing, do receptor cells contain voltage gated sodium ion channels, or do they only contain sodium ion channels that respond to changes in energy level i.e. pressure? The action potential doesn't occur in the receptor cell, right?

    The book isn't really that clear on it, neither is the mark scheme :| and I just can't seem to make sense of it.

    Thank you
    The strength of the pressure doesn't change the size of the action potential, instead it changes the frequency. A light pressure would mean the action potential is less frequent but strong pressure would result in so many action potentials forming. As for your second question, yeah I think they have both sodium ion channels to maintain the resting potential and voltage gated sodium ion channels for when there is a stimulus. An action potential has to occur in the receptor cell for it to actual transmit the message.
    Correct me if i'm wrong please.
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    (Original post by Zoze)
    Hi, just wondering if someone can clarify this question about neurones to me. http://biogishumerus.com/2013/04/25/...s-past-papers/ Just click the link and click on nerves and hormones, scroll down and it's the pacinian corpuscle question from 2008.

    I don't really understand how a change in p.d is caused in the sensory neurone at light and medium pressures? surely the voltage gated sodium ion channels in the sensory neurone membrane don't open until the threshold value is reached? So are there other sodium ion channels that open in response to the generator potentials in the sensory receptor cell membrane? Just one final thing, do receptor cells contain voltage gated sodium ion channels, or do they only contain sodium ion channels that respond to changes in energy level i.e. pressure? The action potential doesn't occur in the receptor cell, right?

    The book isn't really that clear on it, neither is the mark scheme :| and I just can't seem to make sense of it.

    Thank you
    From what I understand, the sensory receptor will have pressure gated Na+ channels (or ____ gated, whatever the stimulus is).
    Hence when pressure is applied to the cell, pressure gated Na+ channels open, Na+ diffuses in and threshold potential is reached, causing voltage gated Na+ channels to open, generating an action potential.😊


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    what's the pathway of gluconeogenesis in the liver to make glucose from other molecules?
    Like amino acids or lipids... what's the pathway to them forming glucose? thanks
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    Could anyone be able to explain how to calculate the net gain of ATP in the question on Page 97 of the textbook and Page 20 of this pdf: http://www.pearsonschoolsandfecolleg...it1Module4.pdf
    thanks in advance
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    I'm scared!

    Any predictions? I have a feeling a lot about photosynthesis and respiration will come up :/

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    (Original post by cinderella25)
    I'm scared!


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    I second that!!
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    What are the grade boundaries like over the past few years for F214? Aiming for an A!
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    Plants that live in the Arctic have a relatively short growing season in which the light intensity is always relatively low. Many species growing in these conditions have a high level of anthocyanin pigments in their leaves. The combined effect of these red pigments with the green chlorophyll makes the leaves appear dark purple or black.
    Suggest why this adaptation is useful in increasing photosynthetic rates.

    How do you answer this?
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    (Original post by tewas)
    Plants that live in the Arctic have a relatively short growing season in which the light intensity is always relatively low. Many species growing in these conditions have a high level of anthocyanin pigments in their leaves. The combined effect of these red pigments with the green chlorophyll makes the leaves appear dark purple or black.
    Suggest why this adaptation is useful in increasing photosynthetic rates.

    How do you answer this?
    I'm pretty sure it's going to have something to do with how different photosynthetic pigments absorb light of different wavelengths. How many marks is it?
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    (Original post by tewas)
    Plants that live in the Arctic have a relatively short growing season in which the light intensity is always relatively low. Many species growing in these conditions have a high level of anthocyanin pigments in their leaves. The combined effect of these red pigments with the green chlorophyll makes the leaves appear dark purple or black.
    Suggest why this adaptation is useful in increasing photosynthetic rates.

    How do you answer this?
    It'll be something along the lines of they absorb a greater range of light wavelengths and reflect less, this means they can maximise the amount of light they absorb and thus the rate of photosynthesis in low light intensities.
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    (Original post by Beni24)
    Glycolysis,links and krebs cycle occurs twice for every glucose molecule? why does this happen again?

    Glycolysis only occurs once per glucose molecule but the link reaction and krebs cycle occurs twice per glucose because 2 pyruvate is produced at the end of glycolysis.
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    (Original post by EllieTaorps)
    It'll be something along the lines of they absorb a greater range of light wavelengths and reflect less, this means they can maximise the amount of light they absorb and thus the rate of photosynthesis in low light intensities.
    yes that is right but could you explain how you worked that out from the info given in the question? thanks
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    Just had a dream I missed the exam and failed it. Lol the pressure is getting to me
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    (Original post by domcandrews)
    Could anyone be able to explain how to calculate the net gain of ATP in the question on Page 97 of the textbook and Page 20 of this pdf: http://www.pearsonschoolsandfecolleg...it1Module4.pdf
    thanks in advance
    Can anyone do this? So confused as to how to do it, They always put some sort of calculation in, and this is the hardest one I've seen! Any help?
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    (Original post by ChoccyPhilly)
    Just had a dream I missed the exam and failed it. Lol the pressure is getting to me
    Same here. This unit is the worst!


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    Guys what is photorespiration? its mentioned in the revision guide that increasing temperature will make the rate of photorespiration greater than rate of photosynthesis but it doesn't actually say what it is???

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    Hi, does anyone know where I can find the OCR June 2014 F214 paper? Looked for it everywhere I can't find it!
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    (Original post by domcandrews)
    Could anyone be able to explain how to calculate the net gain of ATP in the question on Page 97 of the textbook and Page 20 of this pdf: http://www.pearsonschoolsandfecolleg...it1Module4.pdf
    thanks in advance
    Just done it, does that make sense?
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    (Original post by LauraS88049)
    Hi, does anyone know where I can find the OCR June 2014 F214 paper? Looked for it everywhere I can't find it!
    biotutor
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    (Original post by LauraS88049)
    Hi, does anyone know where I can find the OCR June 2014 F214 paper? Looked for it everywhere I can't find it!
    http://www.thebiotutor.com/past-papers3.html
 
 
 
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