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    Thank you so much!
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    (Original post by kimmykim1)
    hey can some one sum up the ethics of using stem cells?
    · Destructed embryos were viable ;
    · idea of ‘right to life’ ;
    · stem cells from unfertilised embryos have fewer objections ;
    · arguments that only adult stem cells should be used because there are no embryos destroyed ;
    · however adult stem cells are limited in use ;
    Hope it helps, i got it from one of the revision notes someone posted on this site.
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    (Original post by kevsamuel)
    Could someone list all the topics that we NEED to know, because I don't want to be studying topics like epistatis if it's not actually in the syllabus.

    Thanks
    Search " Edexcel A - level Biology Specification " into Google and click the first link > that will tell you all the topics you need to know + if there is a topic not in there = it won't be tested ; so no need to bother learning it .

    ~ Good Luck :cool:
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    (Original post by Daniel Atieh)
    Help....shall i write 3 or 4 or 5 or 6 points here? Attachment 221926
    My rule of thumb is write one more point that the number of marks

    Eg. One mark = 2 points

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    (Original post by AbiHem)
    Does crossing over of chromatids happen and then independent assortment happen?
    Or are they complete different things?! IM CONFUSED HELP ME PLEASE ANYONE
    Lol I was stressing out over this they both happen and no that are not the same thing

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    (Original post by diggy)
    Lol I was stressing out over this they both happen and no that are not the same thing

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    Ah thank you! At the same time? Or one after the other?
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    Hi, does anyone know if starch is soluble or not ?
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    (Original post by maryam1996)
    Hi, does anyone know if starch is soluble or not ?
    Starch is insoluble as they are large molecules and basically used as a energy store.
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    What experiment do you guys think will be asked? Do we need to remember the practicals from unit 1 as well?
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    61 in Jan 2009 paper....not bad
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    What's the difference between pits (in cell walls) and plasmodesmata?
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    (Original post by LABONNO)
    Starch is insoluble as they are large molecules and basically used as a energy store.
    Thank you
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    (Original post by Kurraiyo)
    What's the difference between pits (in cell walls) and plasmodesmata?
    Both Pits and Plasmodesmata are involved in cell-to-cell transport but the difference is that in plasmodesmata both cell walls are absent (Primary and secondary cell wall) but the pit only has a secondary cell wall absent ( but primary cell wall is still present) Hope this helps
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    (Original post by bubblegummer)
    What experiment do you guys think will be asked? Do we need to remember the practicals from unit 1 as well?
    we won't be tested on the practicals from unit 1. Only on the ones we've done in unit 2: the experiments should be on the spec http://www.edexcel.com/migrationdocu...4%20250510.pdf
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    How does cellulose microfibrils contribute to the physical properties of plant fibres
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    I actually found the specimen paper a lot easier than the June 2012 paper :dontknow:
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    (Original post by Rickrossmmg)
    How does cellulose microfibrils give plants fibres their function
    -Cellulose microfibrils are made up of 50-80 cellulose molecules
    -A cellulose molecule is composed on beta-glucose, 1-4 glycosidic bonds and are unbranched. Hydrogen bonds occur in adjacent OH groups...

    -Microfibrils have a net-like structure
    -This arrangement ensures that plant fibres are both strong and rigid

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    (Original post by Kurraiyo)
    What's the difference between pits (in cell walls) and plasmodesmata?
    Plasmodesmata is the cytoplasmic channels in cell walls that link adjacent cells together. This enables it to communicate and transport substances between cells.

    Pits are regions in the cell wall that are very thin and are arranged in pairs. The pit in one cell is lined up with the pit of an adjacent cell. This allows the transport of substances only.

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    (Original post by AbiHem)
    Ah thank you! At the same time? Or one after the other?
    Crossing over occurs between homologous pairs during Prophase I. In crossing over, homologous pairs line up and twist around each other at chiasmata; parts of the chromatids break off and join the opposite chromatid. Recombinants are created.

    Random/independent assortment happens during Metaphase 1. The homologous pairs randomly line up on the metaphase plate, so ANY combination of alleles in possible in the 4 daughter cells.

    Hope that helped!


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    haaaated this questionnn:Name:  whyy.JPG
Views: 64
Size:  46.0 KB
    whyyyy no side branches....starch do have 1-6 bonds so why no?
    and last one what they mean exactly? any diagram pleaseee...will appreciate ur answers...thanks
 
 
 
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