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

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    (Original post by jessplease)
    oh okay, thanks! so the number of chromosomes doesn't change unless its a haploid cell?
    Exactly
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    (Original post by parallal)
    I'm not sure about the structures of cellulose and starch. Could someone please explain?

    I know that cellulose is made up of beta glucose and starch is made up of alpha glucose. Cellulose has many Hydrogen bonds between its chains for strength and it forms criss-crossing micro fibrils (also for strength). Starch is spiral-shaped to be compact so it takes up less space, and it is branched so that it can be readily hydrolyzed.

    Is there anything else I need to know?
    Celluose has straight glysocidic bonds.
    Starch has branches. I think so it can hydrolyse them easier as they are shorter chains?
    Starch has amylose and amylopectin. Amylose is the non branched part and amylopectin is the branch. Starch is insoluble in water which is useful as it does not affect water potential so doesn't affect osmosis.
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    (Original post by parallal)
    I'm not sure about the structures of cellulose and starch. Could someone please explain?

    I know that cellulose is made up of beta glucose and starch is made up of alpha glucose. Cellulose has many Hydrogen bonds between its chains for strength and it forms criss-crossing micro fibrils (also for strength). Starch is spiral-shaped to be compact so it takes up less space, and it is branched so that it can be readily hydrolyzed.

    Is there anything else I need to know?
    Starch
    -Made from alpha glucose
    -Joined by condensation [forms glycosidic bonds]

    Features:
    -Compact - able to store a large amount in a small space
    -Insoluble - no effect on water potential
    -Has branches which can be hydrolysed to release glucose

    Cellulose
    -Made from Beta-Glucose
    -Joined by condensation
    -Carbons 1 & 4, 1 & 6
    -Flipping over of alternate molecules

    Features:
    -Unbranched chains lie side by side
    -To form microfibrils
    -Hydrogen bonds link the cross-linkages of chains to give tensile strength

    Starch - Plants
    Glycogen - Animals [Muscles/Liver]
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    I think it's clear to say its the HSW questions that f us all over.
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    (Original post by parallal)
    I'm not sure about the structures of cellulose and starch. Could someone please explain?

    I know that cellulose is made up of beta glucose and starch is made up of alpha glucose. Cellulose has many Hydrogen bonds between its chains for strength and it forms criss-crossing micro fibrils (also for strength). Starch is spiral-shaped to be compact so it takes up less space, and it is branched so that it can be readily hydrolyzed.

    Is there anything else I need to know?
    You may also want to add that starch is the storage compound in plants and it is suitable for this role as it does not affect the water potential of the cell and therefore being insoluble it does not draw water into/out of cells, and it itself does not diffuse out of cells.
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    (Original post by LifeIsGood)
    Starch
    -Made from alpha glucose
    -Joined by condensation [forms glycosidic bonds]

    Features:
    -Compact - able to store a large amount in a small space
    -Insoluble - no effect on water potential
    -Has branches which can be hydrolysed to release glucose

    Cellulose
    -Made from Beta-Glucose
    -Joined by condensation
    -Carbons 1 & 4, 1 & 6
    -Flipping over of alternate molecules

    Features:
    -Unbranched chains lie side by side
    -To form microfibrils
    -Hydrogen bonds link the cross-linkages of chains to give tensile strength

    Starch - Plants
    Glycogen - Animals [Muscles/Liver]
    Thanks so much!
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    (Original post by ??????????????????)
    Celluose has straight glysocidic bonds.
    Starch has branches. I think so it can hydrolyse them easier as they are shorter chains?
    Starch has amylose and amylopectin. Amylose is the non branched part and amylopectin is the branch. Starch is insoluble in water which is useful as it does not affect water potential so doesn't affect osmosis.
    (Original post by ScienceGeek3)
    You may also want to add that starch is the storage compound in plants and it is suitable for this role as it does not affect the water potential of the cell and therefore being insoluble it does not draw water into/out of cells, and it itself does not diffuse out of cells.
    Thanks to you two as well. (:
    I'm feeling a bit more confident about this exam.
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    Hey all, I have just created a thread in the revision forum. It is just a place for people who want to cram this evening and maybe late into the night. Luckily for us our exam is in the afternoon meaning we can sleep in. Please just join and you can ask others for help on concepts or learning things. Join and we can get through the next evening/night to get the best gread we can get. HERE IS THE LINK.


    http://www.thestudentroom.co.uk/show...5#post31700415
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    (Original post by mclovin123)
    Hey all, I have just created a thread in the revision forum. It is just a place for people who want to cram this evening and maybe late into the night. Luckily for us our exam is in the afternoon meaning we can sleep in. Please just join and you can ask others for help on concepts or learning things. Join and we can get through the next evening/night to get the best gread we can get. HERE IS THE LINK.


    http://www.thestudentroom.co.uk/show...5#post31700415
    Lucky you getting to sleep in Most people here have got S1 in the morning I think?
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    (Original post by ??????????????????)
    Lucky you getting to sleep in Most people here have got S1 in the morning I think?
    s1? what is this? Are you talking about biol2?
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    (Original post by ??????????????????)
    Lucky you getting to sleep in Most people here have got S1 in the morning I think?
    Or C2
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    (Original post by mclovin123)
    s1? what is this? Are you talking about biol2?
    Statistics 1.
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    (Original post by ??????????????????)
    Statistics 1.
    damn man, sorry to hear that
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    (Original post by ??????????????????)
    Lucky you getting to sleep in Most people here have got S1 in the morning I think?
    I really hate that they are both on the same day! I'm so gonna flop one of them . Stupid Stats.
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    (Original post by TlanTlan)
    A species is a group of organisms that can reproduce together to produce fertile offspring. The difficulty in establishing this could result from species being rare and hard to make mate in isolation, and the ethical implications of interfering with the organism to get the DNA sample or what-not.

    Taxonomy is the classification of organisms into a hierarchy. The hierarchy simply being large groups containing smaller groups with no overlap, and allowing organisms to be classified by their common ancestor and evolutionary relationship(phylogenetic classification), or grouping into groups of similar phenotypes/characteristics and alleles.

    The ethical implications of antibiotic resistance mean that bacteria have gained a selection advantage as a result of their mutated resistance gene, and due to this modern antibiotics may not work on them, and without use of multiple antibiotics can result in strains of bacteria resistant to multiple antiobiotics. This can result in more suffering for patients and animals who are infected with these strains as they cannot be treated as effectively as well as leading them to die in this time.

    (Original post by ??????????????????)
    -Might be extinct, nocturnal.
    -Because some countries have different names for the same organisms so a scientific name helps to identify what they are talking about.
    -Not sure what you mean? Like testing antibiotics on animals?
    Thanks
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    (Original post by HaimishaParekh)
    I really hate that they are both on the same day! I'm so gonna flop one of them . Stupid Stats.
    I have C2 the same daay! And chem 2 the day after
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    If Fe2+ is green and haemoglobin contains Fe2+ why is our blood red
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    (Original post by liviaaa)
    I have C2 the same daay! And chem 2 the day after
    I have the same as you PLUS economics on Friday along with chem 2, I think I win
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    (Original post by oHellno)
    Yeah, the DNA replicates during interphase, that's why the chromosomes appear as the 'X' shape. Originally, it's just one 'strand', one chromatid. After replication, you have two sister chromatids, which are then separated during mitosis.
    so why does the number of chromosomes stay the same shouldn't it double during interphase and then return to normal at telophase?
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    (Original post by liviaaa)
    I have C2 the same daay! And chem 2 the day after
    Oh my! Thank god, Biol2 is my last exam Good luck for yours though!
 
 
 
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