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

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    how many minutes do we have for essay guys
    and hw many mins should i plan???
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    (Original post by sleungs)
    So if you were asked to define a "stem cell" or a "totipotent cell" what would you say?

    Just read the Wiki article and it seems to me that a zygote is a totipotent cell. There are no other cells which are totipotent. When it divides and develops into an embryo, the cells are then called stem cells? Basically I have no idea what I'm talking about!
    Stem cells are just undifferentiated cells. Totipotent, pluripotent and multipotent cells are types of stem cells. Totipotent stem cells can become all cells, and are present in the early zygote. This ability is lost and cells become pluripotent because these cells can't become placental cells, though they can become all body cells. Multipotent cells are found in adult mammals and can only differentiate into a smaller number of cells E.G. the stem cells in the bone marrow can't become brain cells.

    I think that's right.
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    I would say 5 - 10 minutes planning for an essay, a good fairly detailed plan will give help you write a better essay, 20 - 30 minutes writing.
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    I think tomorrow, I will spend 30 minutes on questions then 30 minutes on the essay. Switch back to finish the questions off and then finally finish the essay as well. That way you have done at least a bit of both.
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    how many marks do you need for full UMS out of 100?
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    possible essay..
    1.) importance enzymes
    Digestion: amylase, maltase, sucrase lactase --> glucose for cells to respire

    Enzyme ATPase to hydrolyse ATP--> movement of myosin heads (contraction), sodium potassium pump, building smaller molecules into larger molecules, secretion (ATP needed to form lysosomes for exocytosis, autolysis, break down of phagocytic vacuole, reuse of useful cell products), Activation of molecues (phosphorylation of glucose in glycolysis)

    Breaking down acetycholine via acetylcholinesterase in muscle contractrion --> recycled/prevent over stimulation

    uses of enzymes in DNA technology: DNA polymerase (add nucleotides in PCR, Sanger method, obtained from bacteria), RNA polymerase (during transcription DNA--> pre mRNA), DNA helicase (during DNA hybridisation when testing how closely related two organisms are)

    Food industry: proteases, lipases and amylase

    talk about enzmes themselves: globular proteins, biological catalysts to lower activation energy

    can anyone think of anything else?
    (i would say that one of the essays could be on DNA tech, but because it has to be synoptic, they're aren't really any synoptic elements we could draw in from other units..)
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    (Original post by Sparkly-Star)
    *Chemo receptors
    *Pressure receptors
    *Influx of sodium ions
    *Temperature
    *Blood glucose conc.
    *Menstrual cycle

    I don't know about the other units haha! :p:
    oh yeah completely forgot about those i feel like ive forgotten everything
    hope this exam goes well otherwise its goodbye uni
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    (Original post by booooom)
    its a past questio. my teacher gave me a list of past essay questions which have come up, what bout the bohr effect frm unit 2--negative feedback??
    what on earth is the bohr effect
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    (Original post by IFondledAGibbon)
    Stem cells are just undifferentiated cells. Totipotent, pluripotent and multipotent cells are types of stem cells. Totipotent stem cells can become all cells, and are present in the early zygote. This ability is lost and cells become pluripotent because these cells can't become placental cells, though they can become all body cells. Multipotent cells are found in adult mammals and can only differentiate into a smaller number of cells E.G. the stem cells in the bone marrow can't become brain cells.

    I think that's right.
    Yes thanks! That's made it really clear
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    (Original post by hahaff)
    oh yeah completely forgot about those i feel like ive forgotten everything
    hope this exam goes well otherwise its goodbye uni
    also, lungs- expiration, inspiration.. atm pressure vs pulmonary pressure..
    and respiration and photosynthesis i guess.. eg, in photosynthesis as RuBP is used up to make GP, TP regenarates it using ATP.. as far as i can remember?
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    (Original post by hahaff)
    what on earth is the bohr effect
    Carbon dioxide reducing haemoglobin's ffinity for oxygen.

    When dissolved in solution, CO2 becomes HCO3, carbonic acid, which can partially denature the haemoglobin, reducing it's oxygen affinity.
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    (Original post by Flux_Pav)
    how many marks do you need for full UMS out of 100?
    depends on the grade boundaries
    hope they are really low this time round
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    (Original post by Vidja)
    Carbon dioxide reducing haemoglobin's ffinity for oxygen.

    When dissolved in solution, CO2 becomes HCO3, carbonic acid, which can partially denature the haemoglobin, reducing it's oxygen affinity.
    i knew that but i didnt knw it was called the bohr effect
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    (Original post by hahaff)
    i knew that but i didnt knw it was called the bohr effect
    Page 152 of the AS textbook if you're interested
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    Urgh panicking big time for this exam.
    Although its my last one <3 Horrayy!
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    (Original post by Vidja)
    Carbon dioxide reducing haemoglobin's ffinity for oxygen.

    When dissolved in solution, CO2 becomes HCO3, carbonic acid, which can partially denature the haemoglobin, reducing it's oxygen affinity.
    It does not denature the haemoglobin, it just displaces the oxygen
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    I am really scared about the weird HSW questions, often the last few questions.
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    (Original post by flowerscat)
    It does not denature the haemoglobin, it just displaces the oxygen
    Oh, really? Thanks. Is it the actual carbonic acid molecule that displaces the oxyegn, or does a CO from the acid displace it or something?

    EDIT: The textbook says the low pH of the acid causes the haemoglobin to change shape?
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    (Original post by Flux_Pav)
    in DNA sequencing, do you pick out only one piece of dna and clone it by PCR ?
    or do you sequence the whole genome by cutting it into pieces ?



    In DNA sequencing, you can do either. As long as you can design some primers that can start off the sequencing. If you were sequencing an entire genome, then it is first cut into pieces by restriction enzymes, inserted into vector, then sequenced. Since you know the sequence of the vector, you will always be able to design primers to start off sequencing.

    and also, how do you know that the fragment that moved the furthest only consisted of one nucleotide?

    it could be any size as long as its the smallest, isn't it?
    Because you are adding four terminator nucleotides.

    The synthesis of the completmentary base to the first base of the sequence can be either by a "normal" base or a terminator base.

    If the terminator base is added, then the first band will correspond to one nucleotide.

    In practice, this does not happen, as you will also have the sequence of the (radiolabelled) primer to account for. So the lowest band = (length of primer + first base)

    Hope this helps.
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    (Original post by Sparkly-Star)
    Page 187, can anyone explain the theory? The last paragraph.
    The one about A-bands and I bands?
 
 
 
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