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

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    does anyone know if we need to know about how virus / fungi cause disease SPECIFICALLY
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    What is cell fractionation?
    Why is there a need to filter the solution?
    Why was the solution placed in a cold, isotonic and buffered solution?
    What is homogenization?
    Describe the process of ultracentrifugation.

    Describe the differences between TEM and SEM.
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    (Original post by Sparkly-Star)
    What is cell fractionation?
    Why is there a need to filter the solution?
    Why was the solution placed in a cold, isotonic and buffered solution?
    What is homogenization?
    Describe the process of ultracentrifugation.

    Describe the differences between TEM and SEM.
    Splitting up the cells into separate organelles?

    To remove debris / cellular waste.

    Cold - reduce enzyme activity
    Isotonic - No osmotic effects on organelles
    Buffered - constant PH, so no enzymes denatures

    Homogenization - Breaking open the cell to release organelles

    1 - Homogenised
    2 - Filtered
    3 - Put in centrifuge, spun at low speed
    4 - Organelles at the bottom are filtered off
    5 - Supernatant respun, at higher speeds etc..

    TEM - electrons absorbed, prepared with heavt metals
    SEM - electrons refected, 3D image, prepared with gold
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    (Original post by emmaaa65)
    monocolonal antibodies are antibodies that are identical in structure and therefore will respond to the same type fo antigen


    what is the difference between passive and active immunity?
    They are genetically identical not just identical. Knowing AQA this will probably the main word needed to get the mark.
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    (Original post by liviaaa)
    All 3 have been on previous mark schemes. You could also mention 3D image, unless it specifies TEM rather than SEM.
    Oh okay cos I would've thought by saying higher resolving power it'd be obvious that you can magnify things better so the wavelength point is more important in that sense? But if there is a 3 marker I will write those. :yep:
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    What's in an oral reyhdration solution, and how does it help diahorea?
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    (Original post by Sparkly-Star)
    Oh okay cos I would've thought by saying higher resolving power it'd be obvious that you can magnify things better so the wavelength point is more important in that sense? But if there is a 3 marker I will write those. :yep:
    Magnification and resolution are different though. Magnification is about enlarging, and resolution is about the ability to distinguish between 2 points.
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    (Original post by liviaaa)
    Describe the structure of an antibody.
    Made out of 4 polypeptide chains, 2 heavy chains and 2 light chains. It has a variable region which has a specific tertiary structure and a constant region that does not change. Ugh I can't do this.
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    (Original post by liviaaa)
    Magnification and resolution are different though. Magnification is about enlarging, and resolution is about the ability to distinguish between 2 points.
    Hmm yeah I guess lol.
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    (Original post by liviaaa)
    What's in an oral reyhdration solution, and how does it help diahorea?
    Water to rehydrate the tissues.
    Potassium, sodium and citrate ions to replace lost ions.
    Potassium to boost appetite.
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    (Original post by Sparkly-Star)
    Made out of 4 polypeptide chains, 2 heavy chains and 2 light chains. It has a variable region which has a specific tertiary structure and a constant region that does not change. Ugh I can't do this.
    Yeah I don't really know what else.. I don'tunderstand, why does it need a variable region if it's specific to one antigen?
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    (Original post by Sparkly-Star)
    What is cell fractionation?
    Why is there a need to filter the solution?
    Why was the solution placed in a cold, isotonic and buffered solution?
    What is homogenization?
    Describe the process of ultracentrifugation.

    Describe the differences between TEM and SEM.
    Cell Fractionation: The process of separating organelles from the rest of the cell.

    Filtration isrequired to separate the organelles from the connective tissue of the cell

    Homogenization is required to break open the plasma membranes and release organelles into solution.

    Solution is cold to prevent enzyme activity, isotonic to prevent osmotic activity (which may shrink/make cells turgid) and bugger tio required to keep PH constant.

    In ultracentrifugation, the solution containing a mixture of organelles is spun in a centrifuge, first at low speed. Sediment forms at bottom = a pellet, firstly the pellet is the nuclei. The solution of lighter organelles at the top is known as supernatant and this is drained off and poured into another tube, put into centrifuge again and spun at a higher speed. This continues untill all organelles are separate. Order = nuclei, mitocondria, lysosomes, ER and ribosomes.

    SEM: Scannig beam of elextrons across specimen, knocks electrons of specimen, gathered in cathode ray tuve to form an image. Lower res and mag than TEM, can be used on thick specimens, can form 3D image. Yet only shows surface of specimen. Long prep time (often needs to be coated in gold), yet specimen can be alive.

    TEM: Electromagnets focus a beam of electrons through specimen, denser parts of specimen absorb more electrons and so show up darker. Higher res and mag than SEM. Yet only used on thin specimens and do not show 3D image. Specimen needs to be dead too.
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    (Original post by Sparkly-Star)
    Water to rehydrate the tissues.
    Potassium, sodium and citrate ions to replace lost ions.
    Potassium to boost appetite.
    I would also talk about how the ions are reabsored into cells out of lumen, lowering water potention, so water moves from l. intestine into cells by osmosis.
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    (Original post by liviaaa)
    Yeah I don't really know what else.. I don'tunderstand, why does it need a variable region if it's specific to one antigen?
    Its exactly the same as an enzymes active site, specific, complementary to one antigen. Needs variable region to make it specific.
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    (Original post by Tericon)
    SEM: Scannig beam of elextrons across specimen, knocks electrons of specimen, gathered in cathode ray tuve to form an image. Lower res and mag than TEM, can be used on thick specimens, can form 3D image. Yet only shows surface of specimen. Long prep time (often needs to be coated in gold), yet specimen can be alive.
    It's not alive - it's in a vacuum.
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    (Original post by liviaaa)
    I would also talk about how the ions are reabsored into cells out of lumen, lowering water potention, so water moves from l. intestine into cells by osmosis.
    Haha I was gonna write that and thought nahh I can't be bothered right now.
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    (Original post by jsmith6131)
    does anyone know if we need to know about how virus / fungi cause disease SPECIFICALLY
    or is it just

    toxin production
    damaging host cells
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    (Original post by Tericon)
    Its exactly the same as an enzymes active site, specific, complementary to one antigen. Needs variable region to make it specific.
    Ohh so it means the variable region changes shape on the different antibodies! I thought it meant on 1 antibody it kept changing shape. Thanks!
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    (Original post by liviaaa)
    I would also talk about how the ions are reabsored into cells out of lumen, lowering water potention, so water moves from l. intestine into cells by osmosis.
    You can also mention use of amino acids to increase co transport of sodium ions
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    any1 has an idea whatt the two 5 markers will be....i know the paper will have 7 questions....got it from the aqa website...since its a 16 page booklet.
 
 
 
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