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

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    (Original post by vickidougal)
    how come adrenaline forms a substrate receptor complex with the receptor on the CSM then? i thought that only applied to enzymes when their active site binds to a substrate
    Plenty of stuff bind to protein receptors on the cell membrane - antibodies and so on. It isn't exclusively enzymes.



    Adrenaline looks like that



    It just needs hydrogen bond from the OH and NH groups (I suspect) with the receptor protein.
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    (Original post by TlanTlan)
    :eek: are you serious?!
    Unfortunately yes. It was the specimen mark scheme though, hopefully for the real exam they'd notice their mistake!
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    (Original post by percy93)
    summation means the body can respond to smaller stimuluses, because the threashold level for neurotransmitter/ action potential can be exceeded more easily, so it's more finely tuned so to speak
    Ahh right, thanks alot!
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    (Original post by ellmell)
    Do we have to know photosynthesis and respiration in as much detail as we did for the january unit for synoptic essays? Because I can only remember the basic equations
    Well, probably not to such a great extent, but you should definitely revise is as they were the key themes of Unit 4.
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    Does anyone have a past papers link? I can only find June 2010, already done that one three times...
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    (Original post by 5mattcolour)
    I got 65 without really revising (I was expecting an epic fail) when I did it as a mock under exam conditions so it can easily be done
    i dont knw how u managed that
    without revision there were some bits where i got full marks
    and some questions where i got no marks at all
    im just hoping that the bio5 is like the bio4 cos i heard there was hardly hsw in bio4
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    (Original post by abzzzg)
    Totipotent cells are undifferentiated, meaning they can develop into ANY cell. Stem cells are totipotent and they are found in the lining of the small intestine, skin, and bone marrow. Also, fertilised eggs are totipotent, technically known as 'embryonic stem cells'. In plants, however, loads of their cells are totipotent, and this is why you can grow a plant from a cutting, but you can't grow a body from a leg!!

    Basically, because every cell in your body contains the same DNA, every cell has the potential to code for ANY protein. However, we don't want that, as for example, we don't need insulin to be coded for and made anywhere else other than beta cells. So...different genes in different cells are turned on or off (expressed/not expressed), depending on the cell function/requirements. This is called gene expression, and is controlled by preventing transcription or breaking down mRNA before it's translated.

    Hope this helps
    your describing pluripotent stem cells. you don't use totipotent cells in research



    Pluripotent cells cannot turn into the blastocyst - but they can turn into everything else.
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    (Original post by abzzzg)
    Does anyone have a past papers link? I can only find June 2010, already done that one three times...
    There's a specimen paper on the AQA website but that's it. They don't run Unit 5 in January.
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    (Original post by LeBubbled)
    There's a specimen paper on the AQA website but that's it. They don't run Unit 5 in January.
    Hmm better try the specimen paper then! Thanks!
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    What are some big synoptic subjects to look up on? So far I've got:

    Structure of carbohydrates and Proteins (For essays)
    Respiration and photosynthesis (For essays)
    How the SAN functions (Relevent to Unit 5)
    How meiosis works (Relevent to unit 5)
    Tests for reducing sugars, starch and proteins (It just seems like it could be a synoptic 2 marker)
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    (Original post by Cyanohydrin)
    your describing pluripotent stem cells. you don't use totipotent cells in research



    Pluripotent cells cannot turn into the blastocyst - but they can turn into everything else.
    Is this in the spec? In the book, all it says is "stem cells also occur at the earliest stage of development of an embryo, these are embryonic cells."
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    Can someone help me with this?

    One of my biology books say that "high blood pressure is detected by baroreceptors, then impulses are sent to the medulla oblongata, sending impulses along parasympathetic newurons, which secrete acetylecholine, which then binds to receptors on the SAN"

    Whereas my other biology book says that " high blood pressure is detected by baroreceptors, then impulses are sent to the center in the medulla oblongata that decreases heart rate, which then increases the frequency of impulses to the SAN via the parasympathetic nervous system"

    What should I say in my exam then?? :/
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    (Original post by abzzzg)
    Is this in the spec? In the book, all it says is "stem cells also occur at the earliest stage of development of an embryo, these are embryonic cells."
    I don't know. Totipotent stem cells are not embryonic stem cells...

    Embryonic stem cells are pluripotent stem cells derived from the inner cell mass of the blastocyst
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    In Kinesis , more turns means organism moves away from unfavourable to favourable env. right? And turns less while they're in the favourable env.?
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    (Original post by ZacVR)
    Haven't seen anything about the error being an issue. If it was then surely in DNA replication , where a full strand is copied, the chance would be highest and yet that is still valid?
    The error rates get higher as the DNA gets longer - hence there is a limit to the size of fragment that can be amplified by PCR. Also, the chances of the polymerase falling off the DNA strand increase. In addition, the chances of non-specific primer binding also increase.
    PCR works best for fragments between 200 bp to 2000 bp.
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    (Original post by NRican)
    In Kinesis , more turns means organism moves away from unfavourable to favourable env. right? And turns less while they're in the favourable env.?
    Well Kinesis is just a non-directional response that changes the rate of turning and speed. It doesn't have to work like that...

    for example

    Orthokinesis: in which the speed of movement of the individual is dependent upon the intensity of the stimulus. Take, for example, the locomotion of a woodlouse in relation to temperature. With increased humidity there is an increase in the percentage time that the woodlouse will remain stationary.
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    (Original post by appleschnapps)
    PCR is used before the restriction endonucleases, so PCR amplifies the entirety of the sample. This will probably be fairly small regardless in genetic fingerprinting. When using genetic fingerprinting in paternity tests, you're working on the basis that half the bands will match with the offspring - you're not specifically picking the paternal DNA in the first place.



    As long as you remember the key features (e.g. replica plating if the antibiotic is going to kill the bacteria that have incorporated the plasmid), you should be fine. Can't help you with the number of marks per question thing though; we don't really have enough to go on yet.
    Hey yh i get that but why will the sample be small, its still a whole piece of dna your extracting??? and you have 46 chromosomes, so would you extract each chromosome in the fingerprinting for parental ones i dont get it?
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    (Original post by Cyanohydrin)
    Well Kinesis is just a non-directional response that changes the rate of turning and speed. It doesn't have to work like that...

    for example
    But in the NT book questions, it says more turns= stays in favourable conditions longer
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    (Original post by NRican)
    But in the NT book questions, it says more turns= stays in favourable conditions longer
    Yeah they could do that, it's not the only example of kinesis - but it is an example of kinesis...
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    (Original post by Cyanohydrin)
    I don't know. Totipotent stem cells are not embryonic stem cells...

    Embryonic stem cells are pluripotent stem cells derived from the inner cell mass of the blastocyst

    Embryonic stem cells (at the 16 cell stage) are totipotent - each cells is capable of regenerating to all the cells in the body, including the umbilical cord (and therefore a new foetus)

    Beyond the 16 cell stage, they differentiate into two layers and become pluripotent, at this stage they can only differentiate into one of the 3 tissue types - digestive organs, skeletal system or nervous system. They cannot develop into umbilical tissue, hence incapable of forming a new foetus.

    Adult stem cells are multipotent, hence not as powerful as embryonic stem cells

    Here is a website which explains this quiet well:

    http://biomed.brown.edu/Courses/BI10...ersatility.htm
 
 
 
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