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AQA BIOL2 Biology Unit 2 Exam - 26th May 2011 watch

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    Oh god. Imagine if the six marker is to do with the plant classification bit :|
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    (Original post by SmithytheDrummer)
    Oh god. Imagine if the six marker is to do with the plant classification bit :|
    What plant classification bit...?
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    What on earth is plant classification?
    What ways are used to determine evolutionary history between 2 organisms?
    what are the features of cellulose, starch and glycogen? I know cellulose is made of beta-glucose, present in plant cell walls, provides turgidity and strength. But whats the role of hydrogen bonds and microfibrills?
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    (Original post by Nuss)
    Need help with mitosis



    could someone explain why the answer is BCDEA

    and this question 5, i have no answers, but it makes no sense

    In B the DNA has unravelled and replicated.
    In C it has condensed to doubled armed chromosomes from 2 sister chromatids attached y the centromere.
    In D the nuclear envelope has been broken down so the chromosomes are free in the cytoplasm.
    In E the centromere has replicated and the spindle fibres are contracting and pulling the chromatids to opposite ends of the cell.
    In A the chromatids are now called chromosomes again.

    In Q5 the pictures are terrible, I can't make it out.
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    Is crossing over a rare process? Q5c June 2010.
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    (Original post by Mina!SS)
    What on earth is plant classification?
    What ways are used to determine evolutionary history between 2 organisms?
    what are the features of cellulose, starch and glycogen? I know cellulose is made of beta-glucose, present in plant cell walls, provides turgidity and strength. But whats the role of hydrogen bonds and microfibrills?
    First one I have no idea.

    Second question DNA hybridisation. Protein immunology and comparing amino acid sequences. You could also do it by looking for similar and different characterisitics but this method was used when DNA hybridisation and protein immunology was not invented.

    Long straight chains with glycosidic bonds are formed between beta glucose molecules. There are rows of these long straight chains.
    The long straight chains are attached by hydrogen bonds. To form microfibrils. Many hydrogen bonds give the structure strength and rigidity.
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    (Original post by Some random guy)
    Is crossing over a rare process? Q5c June 2010.
    Yes.
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    (Original post by Mina!SS)
    What on earth is plant classification?
    What ways are used to determine evolutionary history between 2 organisms?
    what are the features of cellulose, starch and glycogen? I know cellulose is made of beta-glucose, present in plant cell walls, provides turgidity and strength. But whats the role of hydrogen bonds and microfibrills?
    H bonds provide further structural strength between the cellulose chains. Hundreds of these chains linked together are called microfibrils.
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    When is everyone leaving? I live close to my centre so I'll leave at 1:10
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    Urghhhh.
    I have a bad feeling the 6mark question is going to be on Meiosis and genetic variation.
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    (Original post by Some random guy)
    When is everyone leaving? I live close to my centre so I'll live at 1:10
    I'm getting ready now leaving in about 15 minutes do some revision recap in school.
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    (Original post by Limitless)
    I'm getting ready now leaving in about 15 minutes do some revision recap in school.
    GOOD LUCKKKKKKKKK AAH I'm nervous as hell
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    Thank you.
    if we get a 6mark Q on Tissue fluid and how it returns back to the capillary, is mentioning presence of large proteins a mark? how pressure has overcome friction? and lymph vessels?

    Im really feeling the pressure now :/
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    (Original post by Mina!SS)
    What on earth is plant classification?
    What ways are used to determine evolutionary history between 2 organisms?
    what are the features of cellulose, starch and glycogen? I know cellulose is made of beta-glucose, present in plant cell walls, provides turgidity and strength. But whats the role of hydrogen bonds and microfibrills?
    I need to know myself, is it even in our syllabus!
    DNA hybridisation - DNA is obtained from both species, one is radioactively/fluorescent marked, then heated to seperate the DNA strands. As it cools the complementary bases from each strand combine to form hydrogen bonds. More complementary bases in DNA are identified by more hydrogen bonds, so upon heating higher temperature will be needed for two species which are more closely related - hence have a recent ancestor.

    Evolutionary comparisons of proteins - Serum extracted from Species A inject >>> species B. Species B produces antibodies complementary to the antigens of Species A. So these antibodies extracted from Species B and serum extracted from Species which need to be compared (eg. C,D, E...) are mixed. The antibodies will make an antibody-antigen complex with corresponding antigens. These complexes are the precipitate, so more precipitate = more closely related because they contain the same proteins, which are coded by similar amino acids, which are coded by similar nucleotide bases.

    Hydrogen bonds only exist in cellulose because of long unbranched chain and rotation of b-glucose. The cellulose is a polymer of the b-glucose monomers joined by condensation reactions, forming glycosidic bonds. These only exist as layers because of no branching. So.. to connect these layers (cross linkages) together hydrogen bonds form. Microfibrils are basically lots of these b-glucose molecules bonded together to make thin fibrils (hence the name).
    Hope that helped.
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    (Original post by EffKayy)
    GOOD LUCKKKKKKKKK AAH I'm nervous as hell
    Thanks. My dad was trying to get me psyched up. Lol.
    Good luck to you too.
    (Original post by Mina!SS)
    Thank you.
    if we get a 6mark Q on Tissue fluid and how it returns back to the capillary, is mentioning presence of large proteins a mark? how pressure has overcome friction? and lymph vessels?

    Im really feeling the pressure now :/
    Yeah all those things will get you a mark. I hope a question on this does not come back it is the only thing I am weak at.
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    Stuck on 5dii on June 2010. Why is the answer 8?
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    (Original post by Some random guy)
    Stuck on 5dii on June 2010. Why is the answer 8?
    MAXIMUM PAIRS = 2^pairs of chromosomes
    e.g.
    2^3 = 8
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    (Original post by EffKayy)
    MAXIMUM PAIRS = 2^pairs of chromosomes
    e.g.
    2^3 = 8
    I still don't get it
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    I really hope there aren't many questions about the movement of water through plants!
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    (Original post by heavencanwait_)
    What plant classification bit...?
    The bit where they got 565 plant species and mapped 3 genes in order for a more accurate comparisons and a phylogenitic tree can could be constructed.
 
 
 
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